In addition, the 12B-immunoreactive cells were observed around the pars tuberalis closely bordering the median eminence and in the blood vessels of the primary portal plexus in the anterior pituitary gland. 
These data show that all peptides tested are active and supports the concept that their effect is mediated by a target upstream of the pituitary, such as the median eminence..
Finally, necdin is necessary for generation of the full complement of GnRH neurons during mouse development and extension of GnRH axons to the median eminence.
Leptin injected twice daily for 4 days either into the right ventromedial hypothalamus (VMH) or into the right lateral cerebral ventricle (ICV) and using Real-Time Taqmantrade mark RT-PCR, mRNA expression levels of selected genes in the arcuate nucleus-median eminence (ARC-ME) complex were quantitatively measured.
Physiological studies have indicated that these effects occur via a direct activation of the GnRH neurons, and at an unknown site in the median eminence or directly on the gonadotropes.
Lesions in the median eminence (ME) produce a well-known neurological model of polydipsia and polyuria in rats.
In Cape mole-rats, GnRH-1-ir processes are particularly dense within the lateral margins of the median eminence, which is enfolded by a large pars tuberalis of the pituitary gland. Natal mole-rats display GnRH-1-ir processes across the breadth of the median eminence, which is abutted by a relatively small pars tuberalis. In female and male Natal mole-rats, GnRH-1-immunoreactivity in the median eminence is less dense in the reproductive animals; no such difference was found in Cape mole-rats between the breeding and non-breeding seasons.
The present study was designed to assess effects of intracerebroventricular (ICV) injection of leptin and CNTF on gene expression in micropunched hypothalamic arcuate nucleus-median eminence (ARC-ME) complex samples from rats.
Gonadotropin releasing hormone (GnRH) neurons must undergo a complex and precise pattern of neuronal migration to appropriately target their projections to the median eminence to trigger gonadotropin secretion and thereby control reproduction.
Specific radioimmunoassays demonstrated that the increase in PC1/3 and PC2 levels following long-term morphine led to increased TRH biosynthesis as evidence by increased TRH/5.4 kDa C-terminal proTRH-derived peptide ratios in the median eminence.
Kisspeptin immunoreactive varicose fibers extended from the preoptic area to the mammillary nuclei, with important densities especially in the anterior periventricular area and the median eminence (ME).
The median eminence, facial colliculus, striae medullaris, auditory tubercle, and inferior fovea were seen in the majority of cases.
FRAs were present in the nuclei of a few astrocytes in the median eminence and infundibular nucleus of the tuber.
Varicose cell processes emanated from irCOPT neurones, some of which projected caudally and traversed the internal layer of the median eminence, and terminated in the posterior pituitary.
Lowering hypothalamic KAP3 protein levels via intraventricular administration of an antisense oligodeoxynucleotide (AS ODN), resulted in reduced release of both glutamate and GnRH from the median eminence (ME), and delayed the onset of puberty.
Dense aggregations of GnRH1-ir fibres are present in the organum vasculosum of the lamina terminalis and the external zone of the median eminence.
AVP-, but not CRH-immunoreactivity staining in the external zone of the median eminence was increased by testosterone in sham animals, and MPN lesions blocked this increment in AVP.
Cells containing TRH were found in the hypothalamic paraventricular and periventricular nuclei and their projections to the median eminence were corroborated.
In contrast to mammals, teleost fish do not have a median eminence; the anterior pituitary is innervated by numerous neuronal cell types and thus, pituitary hormone release is directly regulated.
Their immunoreactive processes extended into the arcuate nucleus, ventromedial hypothalamus and the median eminence.
Gonadotropin releasing hormone (GnRH)-secreting neurons in mammal's project principally to the median eminence-arcuate (ME-ARC) region where they make contact with basal lamina and open into the pericapillary space of the primary hypophyseal portal plexus.
Using an antiserum raised against RFRP-3, cells were localized to the dorsomedial hypothalamic nucleus/paraventricular nucleus of the ovine brain and shown to project to the neurosecretory zone of the ovine median eminence, predicating a role for this peptide in the regulation of anterior pituitary gland function.
In non-treated rats, stress decreased AT(1) receptor binding in the median eminence and basolateral amygdala, increased AT(2) receptor binding in the medial subnucleus of the inferior olive, decreased AT(2) binding in the ventrolateral thalamic nucleus and increased tyrosine hydroxylase mRNA level in the locus coeruleus.
In the median eminence, the content of ir somatostatin in the terminals decreased in the peripubertal compared to the prepubertal group (P<0.001).
areas that lack a BBB, the median eminence and its close relationship with the hypothalamic arcuate nucleus plays an important role in controlling the entry of blood-borne substances to neurons of the mediobasal hypothalamus. In order to clarify the nature of the BBB in the median eminence-arcuate nucleus complex, we have used immunohistochemistry and antisera to protein components of the BBB-(1) tight junctions, claudin-5 and zona occludens-1 (ZO-1); (2) endothelial cells: (a) all endothelial cells: rat endothelial cell antigen-1 (RECA-1), (b) endothelial cells at BBB: endothelial barrier antigen (EBA), glucose transporter 1 (GLUT1) and transferrin receptor (TfR), and (c) endothelial cells at CVOs: dysferlin; (3) basal lamina: laminin; (4) vascular smooth muscle cells: smooth muscle actin (SMA); (5) pericytes: chondroitin sulfate proteoglycan (NG2); (6) glial cells: (a) astrocytes: glial fibrillary acidic protein (GFAP), (b) tanycytes: dopamine- and cAMP-regulated phosphoprotein of 32kDA (DARPP-32), (c) microglia: CD11b.
Structural constituents of the median eminence, adenohypophysis and neurohypophysis contain elements of glutamatergic transmission, including glutamate receptors and enzymes of the glutamate/glutamine cycle.
The available evidence suggests that glial cells of the median eminence regulate GnRH secretion via two related mechanisms. GnRH axons reach the median eminence, at least in part, directed by basic fibroblast growth factor. It is envisioned that, within the median eminence, soluble factors and adhesion molecules work coordinately to control delivery of GnRH to the portal vasculature..
In the median eminence, the internal and external layer showed strong fluorescence for eGFP after osmotic stimuli and stressful conditions, respectively, again indicating appropriate transport of transgene traslation products.
The medial preoptic area (MPOA) proved to be a major integrating centre, with axon terminals from this region terminating at the median eminence releasing factors into the portal vessels to give a direct route from brain to pituitary.
Oxt-ir fibers were found traveling toward and through the median eminence, as well as in the tenia tecta, septum, and nucleus of the diagonal band of Broca.
Previous studies have harvested CSF for GnRH analysis from the median eminence region, but it is unknown whether GnRH in CSF is restricted to this region. The present study shows: 1) the median eminence region is likely to be the major, if not only, source of GnRH entering the cerebroventricular system; and 2) exogenous GnRH crosses the blood-brain barrier, but extremely high doses are required to elevate CSF concentrations to physiological levels.
Blockaded DA-2 receptors led to different responses in GnRH-R mRNA in various parts of the hypothalamus; increased GnRH-R mRNA levels in the preoptic/anterior hypothalamic area, and decreased GnRH-R mRNA amounts in the ventromedial hypothalamus stalk/median eminence. It is suggested that the increase of GnRH gene expression in the anterior pituitary gland and LH secretion in sulpiride-treated ewes are related with an increase of biosynthesis GnRH with concomitant decreased biosynthesis of GnRH-R protein in the ventromedial hypothalamus/stalk median eminence allowing to an increase of GnRH release..
In the median eminence, kisspeptin and GnRH axons were found in extensive and intimate association. These findings indicate that nonsynaptic pathways of communication in the median eminence should be considered as a possible mechanism of kisspeptin regulation of GnRH release, and provide an anatomical basis for reciprocal control of kisspeptin neuronal activity by GnRH..
Analysis of forebrains of homozygous hpg/GFP-positive mice immunostained for GFP revealed a normal population size and appropriate distribution of GnRH neurons in hpg mice, with immunoreactive neuronal processes present at the median eminence.
In only persistently infected fetuses, encephaloclastic lesions resulting in pseudocysts were observed in the subependymal zone in the region of the median eminence and adjacent corona radiata as well as in the region of the external capsule associated with lenticulostriate arteries.
In addition, CCK mRNA was also detected in the external zone of the median eminence where axons of the neuroendocrine hypophysiotropic systems terminate.
Gal-immunoreactivity was first observed in the brain just after hatching in anterior preoptic area, infundibular area, median eminence and pars distalis of the pituitary as well as in the olfactory epithelium. In the median eminence and pars distalis of the pituitary many Gal-ir fibers were found during development indicating that Gal may play a role in the modulation of hypophyseal secretion.
Gpr54 expression was detected outside of the median eminence, in the pars tuberalis.
This study measures the release of kisspeptin-54 in the stalk-median eminence (S-ME) during puberty and examines its potential role in the pubertal increase in LHRH-1 release in female rhesus monkeys.
The push-pull perfusions of the infundibular nucleus-median eminence (IN/ME) were made in lactating ewes (n=7) twice, to identify dopamine (DA)-derived salsolinol and the changes in its extracellular concentration in response to suckling.
The majority of these juxtapositions were found in the infundibular nucleus/median eminence where NPY-IR fiber varicosities often covered a significant surface area of the GHRH neurons.
In the rat, the sexual dimorphism in growth hormone release is driven by sex steroids, and is suggested to result mainly from differences in somatostatin (SOM) release patterns from the median eminence.
Leptin receptors are localized in several regions of the brain implicated in regulation of energy balance and reproductive function, including the arcuate nucleus/median eminence, paraventricular nucleus, and ventromedial nucleus.
Most SOM-ir cells were found in the preoptic area and hypothalamus and abundant SOM-ir fibres coursed along the hypothalamic floor towards the median eminence, suggesting a hypophysiotrophic role for SOM in sturgeon.
However, as in other vertebrates, TRH neurons were abundant in the hypothalamic nuclei that presumably project to the median eminence and the neural lobe of the hypophysis.
During puberty, modifications in the morphology and chemistry of astrocytes and tanycytes in the hypothalamus and median eminence influence the maturation of the neuronal circuits controlling the secretion of GnRH. During adult reproductive life, the glial cells participate in the transient remodeling of neuronal connectivity in the preoptic area, the arcuate nucleus, the median eminence, and other brain regions involved in the control of reproduction.
In diencephalon, moderate staining was found in all thalamic nuclei but was strong in medial habenular nucleus and the hypothalamic nuclei including suprachiasmatic nucleus, optic chiasm, arcuate nucleus and median eminence.
Ten minutes after ewe killing, sagittal midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus with the median eminence, 2 mm thick, 2 per sheep) were dissected, placed in oxygenated minimum essential media-alpha (MEM-alpha) at 4 degrees C and within 2 h were singly perifused at 37 degrees C with oxygenated MEM-alpha (pH 7.4; flow rate 0.15 ml/min), either with or without E(2) (24 pg/ml).
This global objective comprises three major aims: (1) to analyze the possible differential MTX effects in norepinephrine and serotonin concentration an in serotoninergic metabolism in anterior, mediobasal and posterior hypothalamus and median eminence; (2) to evaluate effects induced by MTX exposure on gonadotropins and testosterone; 93 to elucidate whether the regulatory interactions in the hypothalamic-pituitary-testicular axis are modified by this pesticide. We can conclude that MTX exposure: (1) could exert differential effects in norepinephrine and serotonin concentration an in serotoninergic metabolism in anterior, mediobasal and posterior hypothalamus and median eminence, being the anterior hypothalamus the most sensitive region to the pesticide; (2) could inhibit LH and testosterone secretion without changing FSH; (3) four potential pathways might be involved in MTX effects on testosterone secretion (changing LH secretion; modifying serotonin and norepinephrine at the hypothalamic level; alterating the direct neural pathway between brain and testes; and/or by a direct effect in testes)..
From the hypothalamic magnocellular nucleus, CARTp-containing axons run to the neurohemal median eminence, and to the neural pituitary lobe to form neurohemal terminals, as shown by immunoelectron microscopy.
Relative staining area for corticotropin-releasing hormone or neurophysin II, a vasopressin carrier protein, was increased in the external zone of the median eminence in vehicle control, but was equivalent to that of intact control in the dexamethasone-injected group. Dual-labeling experiments revealed no colocalization of NPY with hypophysiotropic or other peptides examined in single fibers of the median eminence.
This provides further evidence for the possible role of the pituicytes in controlling the release of the pituitary hormones given that, in teleost fishes, there is no distinct portal system or true median eminence..
In the present study, we examined enzyme activity and phosphorylation state of tyrosine hydroxylase (TH) in the stalk-median eminence of cycling female rats on proestrus and estrus and related these to circulating progesterone levels. Our study suggests that decreased TH phosphorylation at Ser-19, Ser-31, and Ser-40 contributes to the decline in TH activity in the stalk-median eminence on proestrous afternoon and that progesterone may cause this initial cytoplasmic response of TH dephosphorylation..
Bromodeoxyuridine incorporation was lower (P < or = 0.01) in 6-month PRL-treated normal mice than in 6-month PRL-treated dwarfs in the subventricular zone of the lateral ventricle and in the dentate gyrus, and lower (P < or = 0.05) in 4-month untreated dwarfs than in 4-month untreated normal mice in the median eminence and the periventricular area surrounding the third ventricle.
Neurotransmitter concentrations [ dopamine, gamma-aminobutyric acid (GABA) and taurine] were measured by high pressure liquid chromatography in the median eminence and the pituitary. Dopamine and GABA concentrations in the median eminence or in the adenohypophysis remained unmodified by moderate beer or ethanol consumption.
Cell bodies and terminals containing these neuropeptides are localized in the suprachiasmatic nucleus (SCN) and median eminence, respectively. Orbital enucleation combined with pinealectomy (Ex plus Px) decreased the expression of fGRP precursor mRNA and content of mature fGRP and fGRP-RPs in the diencephalon including the SCN and median eminence.
Salusin-beta-LI fibres and varicosities in the internal zone of the median eminence and the neurohypophysis were also increased after osmotic stimuli.
Further, there was no GnIH-ir labeling in the median eminence on either capture dates, suggesting that GnIH is not released to the pituitary gland via the portal vein at this time of year, but there were fewer GnIH-ir fibers in the preoptic area of birds caught during the monsoon season.
Activation of micro opioid receptors decreased GnRH mRNA levels in the hypothalamus and led to complex changes in GnRH-R mRNA: an increase of GnRH-R mRNA in the preoptic area, no change in the anterior hypothalamus and decrease in the ventromedial hypothalamus and stalk/median eminence.
Whereas the presence of [ 125I]pPYY(3-36)-related labeling was detected in the area postrema, subfornical organ, and median eminence.
GnRH-R mRNA at different concentrations was found throughout the preoptic area, anterior and ventromedial hypothalamus, stalk/median eminence and in the anterior pituitary gland. The highest GnRH-R mRNA levels were detected in the stalk/median eminence and in the anterior pituitary gland.
Although numerous investigators in 1970s to 1980s have reported the distribution of LH-RH nerve fibers in the median eminence, a few LH-RH fibers have been shown to be present in the pars tuberalis.
Immunoreactive contactin is most abundant in GnRH nerve terminals projecting to both the organum vasculosum of the lamina terminalis and median eminence, implying GnRH axons as an important site of contactin-dependent cell adhesiveness.
GnIH immunoreactive fiber terminals were present in the external layer of the median eminence in addition to the preoptic area and midbrain, where GnRH-I and GnRH-II neuronal cell bodies exist, respectively.
Moreover, to determine possible mechanisms involved in parity-mediated changes in prolactin secretion, both dopamine utilisation within the arcuate nucleus/median eminence and expression of dopamine D(2) receptor mRNA (short and long forms) in the anterior pituitary were measured across the afternoon of pro-oestrous in reproductively experience and inexperienced females.
Previous studies in male rats have demonstrated that the orexigenic peptide galanin (GAL), in neurones of the anterior parvocellular region of the paraventricular nucleus (aPVN) projecting to the median eminence (ME), is stimulated by consumption of a high-fat diet and may have a role in the hyperphagia induced by fat.
The expression of PSA-NCAM and glial fibrillary acidic protein (GFAP) on GnRH cell bodies and axon terminals in the medial preoptic area (mPOA) and median eminence-arcuate (ME-ARC) region of hypothalamus was studied in the proestrous phase of cycling rats treated with alpha-adrenergic receptor blocker phenoxybenzamine (PBZ) and gamma-aminobutyric acid (GABA) by using dual immunohistofluorescent staining and Western blot hybridization.
Within 10 min of ewe killing, saggital midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus along with the median eminence, 2-mm thick, two per ewe) were dissected, placed in oxygenated minimum essential media (MEM)-alpha at 4 degrees C and within 2 h were singly perifused at 37 degrees C with oxygenated MEM-alpha (pH 7.4; flow rate 0.15 ml/min), either with or without E(2) (24 pg/ml).
The aim of this study was to investigate the effects of valproic acid treatment on the expression of gonadotropin releasing hormone, gamma amino butyric acid and polysialylated form of neural cell adhesion molecule (PSA-NCAM) a marker of neuronal plasticity in the median preoptic area (mPOA) and median eminence-arcuate (ME-ARC) region having GnRH neuron cell bodies and axon terminals, respectively.
Salsolinol does not alter the dopamine release in median eminence in vitro, providing evidence for the lack of interaction with presynaptic D2 dopamine receptors.
Migrating GnRH-1 neurons follow a branch of the vomeronasal nerve caudally into the hypothalamus, where they extend processes to the median eminence and halt their migration. The release of GnRH-1 into the capillaries of the median eminence starts the cascade that activates pituitary gonadotropin (luteinizing hormone and follicle-stimulating hormone) production and secretion.
Hypothalamic growth hormone-releasing hormone (GHRH) mRNA and immunoreactive (IR) GHRH dramatically decreased (P < 0.01 and P < 0.001) in the old rats, as did median eminence IR-GHRH. Decreases of hypothalamic IR-somatostatin (SS; P < 0.001) and SS mRNA (P < 0.01), and median eminence IR-SS were found in old rats as were GHS receptor and IGF-I mRNA (P < 0.01 and P < 0.05).
the median eminence of the hypothalamus). In line with these light microscopy data, ultrastructural examination of GnRH-immunoreactive neurones showed numerous glial cells in direct apposition to pre-embedding-labelled GnRH cell bodies and/or dendrites in the infundibular nucleus, whereas postembedding immunogold-labelled GnRH nerve terminals were often seen to be enwrapped by glial cell processes in the median eminence.
(2) Other female rats were randomly divided into median eminence (ME) lesions group and control group, which were used to observe the influence of hypothalamic ME lesion on the effect of EA of CV4 in regulating GnRH, LH and estradiol (E2) levels.
The increase in response to sodium chloride was significantly greater in groups E3/E4 and E2 than in the non-lesioned group and in animals with polydipsia induced by lesion of the median eminence.
Within the median eminence of the hypothalamus, alterations of the anatomical relationship that exists between GnRH axon terminals and ependymoglial cell processes belonging to tanycytes regulate the direct access of GnRH neurosecretory axons to the vascular wall. It is becoming increasingly clear that among the different factors that may be involved, glial cells use growth factor members of the epidermal growth factor (EGF) family, acting via receptors endowed with tyrosine kinase activity, to produce morphological changes and release neuroactive substances that directly excite nearby neurons, whereas endothelial cells of the median eminence employ nitric oxide to induce neuroglial plasticity and facilitate GnRH release..
SSTR1 is strongly localized in neurons in all major hypothalamic nuclei as well as in nerve fibers in the zona externa of the median eminence and the ependyma of the third ventricle. In contrast, SSTR3 is localized primarily in the paraventricular nucleus, dorsomedial hypothalamic nucleus, arcuate nucleus, and median eminence. SSTR4-like immunoreactivity is mainly confined to the arcuate nucleus, ventromedial hypothalamic nucleus, median eminence, and ependymal cells of third ventricle, with the rare SSTR4-positive neuron in the paraventricular nucleus. SSTR5 is the least expressed subtype occurring only in few cells in the inner layer of the median eminence.
BACKGROUND: Dopamine release from tuberoinfundibular dopamine neurons into the median eminence activates dopamine-D2 receptors in the pituitary gland where it inhibits lactotroph function.
In addition, a prominent TPH2-IR fiber network was found in the human median eminence.
Compared to HSR monkeys, SS monkeys exhibited a significantly higher number and density of GnRH cell bodies, as well as a higher number of soma with extremely robust expression of GnRH mRNA, but SS monkeys exhibited a lower density of immunostained GnRH fibres in the median eminence.
In addition, almost all GnRH fibers and terminals in the external zone of the median eminence, the site of neurosecretory release of GnRH, also colocalized OFQ.
Phospho-EF2 was localized in the soma of the neurons in PVN and SON, and in the swellings of the median eminence where axonal tracts of the neurons in the PVN and SON exist.
The arcuate nucleus-median eminence area, a region with a weak blood-brain barrier, contains at least two neuronal cell populations that exert opposing actions on energy balance.
We assessed the possible link between endothelin receptor mediated phosphoinositide breakdown and NO/cGMP signaling pathways in rat arcuate nucleus-median eminence fragments (AN-ME), brain structures known to contain a rich plexus of nitric oxide synthase (NOS)-containing neurons and fibers, together with densely arranged endothelin ETB-receptors-like immunoreactive fibres.
In vivo 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposure caused an initial decrease (by 4 h) in dopamine (DA) in brain regions containing axon terminals of TIDA (median eminence [ ME]), NSDA (striatum [ ST]) and MLDA (nucleus accumbens [ NA]) neurons.
Migration of GnRH neurons into the hypothalamus appears normal with appropriate axonal connections to the median eminence and total GnRH content.
These structures include the circumventricular organs (organum vasculosum of the lamina terminalis, subfornical organ, area postrema), some of the ependymal cells along the wall of the ventricles, tanycytes in the third ventricle's ependyma and the median eminence, as well as in the epithelial cells of the choroid plexus in the lateral, third and fourth ventricles.
In control rats, median eminence dopamine (DA), serotonin (5-HT), gamma-aminobutyric acid (GABA), and taurine levels exhibited two maxima, the major one preceding prolactin release and a second one during the first part of the resting phase. median eminence DA and 5-HT turnover (as measured by 3,4-dihydroxyphenylacetic acid, DOPAC/DA, and 5-hydroxyindoleacetic acid, 5-HIAA/5-HT ratio) showed a single maximum preceding prolactin, at 0100 h. Ethanol treatment did not affect median eminence DA or 5-HT levels but it decreased significantly their turnover rate. Ethanol intake suppressed the night peak in median eminence GABA and taurine (at 0100 h) as well as the midday peak of GABA.
CRH neurons project not only to the median eminence but also into brain areas where they, e.g., regulate the adrenal innervation of the autonomic system and affect mood.
In addition to the OFC variations, quantitative immunohistochemistry indicated that the chronic stressor treatment increased CRH immunoreactivity in the median eminence of C57BL/6ByJ mice, but co-expression of CRH and arginine vasopressin (AVP) immunoreactivity was not provoked by the stressors.
The purpose of this study was to test the hypothesis that IL-6 in the stalk median eminence (SME) can be directly involved in stimulating ACTH secretion in response to acute stress in female swine.
CB1-IR innervation of the arcuate, ventromedial, dorsomedial, and paraventricular nuclei and the external zone of the median eminence corroborated the important role of CB1 in the regulation of energy homeostasis and neuroendocrine functions. In conclusion, the study revealed the dense and differential CB1-IR innervation of most hypothalamic nuclei and the median eminence of the mouse brain.
Also, in contrast to the controls, we found in hypertensives a very high number of CRH fibers running from the most rostral part of the Pa to the median eminence and innervating the caudal part of the suprachiasmatic nucleus (SCh).
The RT-PCR (reverse transcription polymerase chain reaction) technique was used to analyze GnRH mRNA and GnRH-R mRNA in the preoptic area, anterior and ventromedial hypothalamus, and GnRH-R mRNA in the stalk/median eminence and anterior pituitary gland of follicular ewes subjected to short (3 h during one day) or prolonged (5 h daily during four consecutive days) footshock stimulation. In short stressed ewes the significant augmentation of mRNA encoding GnRH-R was detected in the preoptic area, entire hypothalamus, stalk/median eminence and anterior pituitary gland.
The internal and the external layer of the median eminence showed numerous bundles of immunostained axons.
Tanycytes comprise a heterogeneous population of specialized cells of glial origin that line the floor and ventrolateral walls of the third ventricle between the rostral and caudal limits of the hypothalamic median eminence. While morphologic and ultrastructural features suggest a role as barrier cells, creating separate compartments between the cerebrospinal fluid, median eminence and hypothalamus, tanycytes likely have multiple other important functions that have yet to be fully elucidated.
Immunoreactive cell processes were detected mostly in the internal layer of the median eminence.
At the level of the median eminence at the base of the brain, where GnRH and other hypothalamic releasing hormones are secreted into the capillary system leading to the anterior pituitary gland, there is non-synaptic regulation of neurohormone release by a number of central neurotransmitters. Western blots of fractionated median eminence support the presence of NMDAR1 in subcellular fractions containing large dense-core vesicles.
BACKGROUND AND PURPOSE: Hypothalamic dopamine (DA), the physiological regulator of pituitary prolactin (PRL) secretion, is synthesized in the neuroendocrine dopaminergic neurons that projects to the median eminence and the neurointermediate lobe of the pituitary gland. Immunohistochemistry, using antibodies raised against to native as well as phosphorylated TH were used to compare their distributions in the arcuate nucleus-median eminence region. On the other hand, systematic application of the alpha-methyl-p-tyrosine that inhibits TH activity located in DA terminals of the median eminence and the neurointermediate lobe, resulted in the most significant elevation of PRL.
Meantime, increased levels of immunoreactive ANP were measured in the median eminence, due to the accumulation of the peptide in the transected axons centrally to the transected stalk and in the paraventricular nucleus.
Using the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) technique, the gonadotropin releasing-hormone (GnRH) mRNA and GnRH receptor (GnRH-R) mRNA were analyzed in the preoptic area (POA), anterior (AH) and ventromedial (VM) hypothalamus, stalk/median eminence (SME) and anterior pituitary gland (AP) of anestrous ewes subjected to short or prolonged footshock stimulation.
For instance, it was found that dopamine may be released as a prolactin inhibitory factor from the median eminence, indicating an alternative mode of dopamine communication in the brain.
Nineteen adult females (n = 8 ovary-intact in the mid-follicular phase; n = 11 ovariectomised) were fitted with long-term cranial pedestals, and a push-pull cannula was temporarily placed in unique locations within the pituitary stalk-median eminence (S-ME) 2 days prior to each PPP session.
Here, using immunohistochemistry, we explored how this applies to the postnatal development and masculinization of the neurokinin B (NKB)-containing system of the arcuate nucleus/median eminence complex (ARC/ME).
The VP/CRH coexpression within PVN and median eminence was investigated by double immunocytochemistry. VP-immunoreactive neurons also coexpressed CCK within PVN and median eminence of control and stressed jerboas.
Expression of TGFalpha mRNA was induced in the median eminence by the stimulus of long days, and this induction was observed at dusk on the first long day. Expression analysis of epidermal growth factor receptors revealed strong expression of erbB4 and weak expression of erbB1 and erbB2 in the median eminence.
In the hypothalamus, high density of CTLA-2alpha mRNA labeling was seen in the suprachiasmatic nucleus (Sch), optic tract, arcuate nucleus, and median eminence.
In the present study, AVP-enhanced green fluorescent protein (eGFP) transgenic rats were used to investigate changes in AVP-eGFP expression in the hypothalamic paraventricular nucleus (PVN) and the median eminence (ME) upon exposure to stress conditions.
The expression of PPT A mRNA significantly decreased at 10d in most of the brain regions of MSG-treated mice including the cerebral cortex (CC), hippocampal subregions of CA1, CA2 (CA1, CA2), habenula nucleus (HAB), hypothalamic periventricular nucleus (PE), hypothalamic arcuate nucleus (AR), median eminence (ME), amygdala nucleus (AMY), endopiriform nucleus (EN), and hypothalamic ventromedial nucleus (VMH) and dorsomedial nucleus (DMH).
Quantitative RT-PCR revealed that the KiSS-1 mRNA level was significantly lower in the arcuate nucleus (ARC)-median eminence region in lactating ovariectomized (OVX) and estrogen-treated OVX rats than in nonlactating controls. GPR54 mRNA levels were significantly lower in lactating than nonlactating rats in the anteroventral periventricular nucleus, but the levels in lactating mothers of the preoptic area and ARC-median eminence were comparable with nonlactating controls.
The contents of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) in the median eminence (ME) of the male rats decreased during restraint stress; however, the fluctuations in CRH and AVP were eliminated by NBQX administration.
Most of the SOM-ir neurons were found in the preoptic area and hypothalamus and showed a clear projection to the median eminence.
Orexinergic fibres project to the septal-preoptic and arcuate nucleus-median eminence regions--two areas of the brain directly involved in the synthesis and release of gonadotropin-releasing hormone (GnRH).
The EPL can be located at the median eminence or at the path of the pituitary stalk. The frequency of the location of EPL was similar in patients with VPS and NPS: 35% at median eminence and 65% at the path of the stalk. CONCLUSIONS: ACTH deficiency is frequent in patients with hypopituitarism and NPS (85%), the location of EPL at the median eminence was not predictive of the hormonal profile [ isolated GH deficiency (IGHD) or CPHD], and LHX4 and HESX1 genes mutations remain rare causes of hypopituitarism associated with EPL..
As in other mammals, VP-immunoreactive (-ir) somata were found in the paraventricular (PVN) and supraoptic nuclei (SON) and VP-ir projections from these nuclei ran through the internal and external zone of the median eminence.
Gonadotropin-releasing hormone (GnRH) neurons arise in the olfactory placode, migrate into the preoptic area (POA), and then extend axons to the median eminence during embryogenesis.
The present studies were aimed to map the neuronal sources of VGLUT2 in the median eminence and the posterior pituitary, the main terminal fields of hypothalamic neurosecretory neurons. Dual-label immunofluorescent studies of the median eminence and posterior pituitary to determine the subcellular location of VGLUT2, revealed the association of VGLUT2 immunoreactivity with SV2 protein, a marker for small clear vesicles in neurosecretory endings. These data suggest that neurosecretory neurons located mainly within the paraventricular, anterior periventricular and supraoptic nuclei and around the organum vasculosum of the lamina terminalis and the preoptic area secrete glutamate into the fenestrated vessels of the median eminence and posterior pituitary.
Labelled fibres and terminals were located in the external and internal zones of the anterior and posterior median eminence.
LHRH, GABA, and glutamate levels in the stalk-median eminence before and after lesions were assessed over two 6-h periods (0600-1200 and 1800-2400) using push-pull perfusion.
Salsolinol did not affect the in vitro release of dopamine (DA) in the median eminence, and did not inhibit the L-DOPA induced increase of DA level in the median eminence. Using tissue catecholamine contents as indicators of the interaction between salsolinol and 1MeDIQ we found no interaction between these two agents to explain the changes in prolactin release in the median eminence, lobes of the pituitary, superior cervical and stellate ganglion.
In support of a hypothalamic site of action, we found that, after intraperitoneal injections, anti-FGFR1c (IMC-A1), but not a control antibody, accumulated in the median eminence and adjacent mediobasal hypothalamus and that FGFR1c is enriched in the hypothalamus of mice.
While mifepristone decreased the intensity of TH immunoreactivity in the arcuate and periventricular nuclei and in fibers of the median eminence, naloxone treatment had no further effect.
Projection fibers also coursed through the tuberal hypothalamus into the median eminence.
The study was conducted to determine gene expression of short form of leptin receptor (OB-Rs) using real time RT-PCR in distinct tissues of the central nervous system (medial basal hypothalamus, preoptic area, stalk median eminence), pituitary and reproductive tract (corpus luteum, ovarian stroma, endometrium, myometrium, and trophoblast) in pigs during luteal phase of the cycle and early gestation.
Majority of the GHRH neurons projecting to the median eminence is situated in the arcuate nucleus and the somatostatin neurons in the anterior periventricular nucleus.
In addition, we observed dense to moderate NEI innervation of areas related to reproduction, including the organum vasculosum of the lamina terminalis, the anteroventral periventricular nucleus (AVPV) and the median eminence. In the median eminence, NEI varicosities and terminal-like structures were in close proximity to blood vessels and GnRH fibers. Our results suggest that NEI might induce LH secretion in one of the following ways: by direct release into the median eminence, by modulation of GnRH neurons located in the preoptic area, by modulation of the GnRH terminals located in the median eminence or by an additive effect involving other neurotransmitters or neurohormones.
The fibers of these cells extend to circumventricular organs (CVOs) and to astrocytes located inside the parenchyma of key autonomic regulatory hypothalamic areas, with highest densities in the supraoptic nucleus (SO), arcuate nucleus (Arc), area postrema (AP), median eminence (ME), medial preoptic nucleus, tuber cinereum, and accessory neurosecretory nuclei.
In these rats, salt loading for 5 days caused a marked increase of the eGFP fluorescence in the magnocellular divisions of the paraventricular nucleus (PVN), the supraoptic nucleus (SON) and the internal layer of the median eminence.
Because CCK is involved in the phenotypical plasticity of CRH-containing neurones in response to an environmental stress, we also explored their coexpression by double immunocytochemistry within the PVN and the median eminence (i.e.
Cells expressing DBI mRNA were mostly observed in the arcuate nucleus, the median eminence and the ependyma bordering the third ventricle. In the median eminence and the ependyma bordering the third ventricule, the DBI gene expression was decreased in ADX rats and a single injection of corticosterone to ADX rats induced a significant increase in DBI gene expression at 3 and 12 h time intervals without completely restoring the basal DBI mRNA expression observed in intact mice. In the median eminence and arcuate nucleus, neither CX or dihydrotestosterone administration modified DBI mRNA levels.
GnRH-I cell bodies are located primarily in the preoptic-septal region and primarily project to the median eminence.
In adult animal, hypophysectomy induced a significant increase in NOS-IR in the supraoptic (SON), paraventricular nuclei (PVN) and median eminence (ME) by 3 days post-lesion. Following hypophysectomy, a large number of fibers were observed in the contact zone of the median eminence and the adjacent lumen of the third cerebral ventricle (V3) in adult rats, whereas few fibers could be found in the lumen of the V3 in the immature rats after the same injury.
PKR2 mRNA is detected throughout the brain, with prominent expression in olfactory regions, cortex, thalamus and hypothalamus, septum and hippocampus, habenula, amygdala, nucleus tractus solitarius, and circumventricular organs such as subfornical organ, median eminence, and area postrema.
A dense plexus of double-labeled prodynorphin/proNKB-ir fibers was found within the arcuate nucleus extending to the median eminence and throughout the periventricular zone of the hypothalamus.
Immunostaining for AVT confirmed that the lesions placed in the region of the median eminence virtually eliminated AVT located in the neurohypophysial tract, and the pars nervosa.
The cell bodies and terminals containing this peptide were localized in the suprachiasmatic nucleus and median eminence, respectively.
D2 immunoreactivity is prominent in glial cells of the infundibular nucleus/median eminence region and in tanycytes lining the third ventricle.
We have previously shown that luteinising hormone (LH)-surge associated changes in hypothalamic neuropeptide Y (NPY) gene expression and median eminence (ME) NPY levels seen in young rats do not occur in middle-aged (MA) rats.
The outer layer of the median eminence displayed numerous fibers located close to the portal system, while scarce fibers were seen in the inner median eminence and neural lobe of the hypophysis.
Immunohistochemistry with the same anti-oxytocin antibody detected strong staining in the neurohypophysis and in few fibers in the inner zone of the median eminence, which was not abolished by pre-adsorption of this antibody with oxytocin, vasopressin, vasotocin or mesotocin and might not be attributed to oxytocin.
Successfully transplanted hpg mice with preoptic area grafts contained GnRH-positive neurons, consistent with our previous experience, and the host median eminence was innervated by GnRH immunoreactive fibers.
The median eminence and area postrema are characterized by a deficiency of the blood-brain barrier.
The hypothalamic infundibular area is located outside the blood-brain barrier and includes, the ventromedial arcuate nucleus (vmARC) sensing circulating substances, and the median eminence (ME) where neurohormones are released into the hypothalamo-hypophysial vasculature.
We examined the effects of VGF on growth hormone (GH) expression and secretion in porcine pituitary slices, incubated alone (group 1) or with stalk median eminence (SME) (group 2).
Fibres that stained positively for both DYN and NKB were seen in the arcuate nucleus, where they formed close appositions with DYN/NKB-positive neurones, and in the external zone of the median eminence.
In the study we evaluated the effects of infusion of exogenous leptin to the third ventricle of the brain on the expression of immunoreactive (ir) neuropeptide Y (NPY) neurons in the hypothalamus and ir gonadotrophin releasing hormone (GnRH) nerve terminals in the median eminence of prepubertal lambs in the conditions of short fasting. In conclusion, the enhanced by fasting immunoreactivity of the ARC NPY perikarya and varicose nerve fibers and restrained immunoreaction of GnRH terminals in the median eminence were reversed by exogenous leptin.
In addition, CART is present in the majority of hypophysiotropic TRH neurons and in TRH-containing axon terminals adjacent to the capillary vessels in the median eminence.
In contrast to colocalization within cell bodies, GnRH fibers in the median eminence did not colocalize GABA-B receptor subunits.
D2 enzyme activity was detectable in the infundibular nucleus/median eminence (IFN/ME) region coinciding with local D2 immunoreactivity in glial cells.
With immunoelectron-microscopic double labeling, we found co-localization of oxytocin and sex hormone binding globulin in a portion of the large dense-core vesicles in paraventricular and supraoptic perikarya and in axonal varicosities in the median eminence and in the posterior lobe. Our observations show that SHBG is processed, transported and stored along with oxytocin suggesting that SHBG is released from nerve terminals in the posterior lobe, the median eminence and possibly the brain similarly to and in conjunction with oxytocin..
Stained fibers occurred in the median eminence and infundibulum. Double immunofluorescence staining showed coexistence of these substances in axonal varicosities in the median eminence.
CBG was also observed in widespread axonal projections throughout the lateral hypothalamus, the median eminence and the posterior pituitary lobe.
Six TFs of GnRH neurons were found including the organum vasculosum of lamina terminalis (OVLT), preoptic recess (POR), hypothalamic recess (HR), lateral septum adjacent to the ventral horn of the lateral ventricle (SL-VLvh) associated with the choroid plexus, subseptal organ (SSO), and external zone of the median eminence.
Numerous varicose kp10-ir fibers were found in the preoptic area where GnRH neurons reside and in the median eminence, seemingly projecting around small capillaries in its external zone.
Therefore, in the present study, an expression of genes coding for leptin and long-form leptin receptor (Ob-Rb) was determined by a semiquantitative reverse transcription polymerase chain reaction (RT-PCR) in the discrete areas of porcine hypothalamus (medial basal hypothalamus - MBH, preoptic area - POA, stalk median eminence - SME) and pituitary (anterior - AP and posterior/neural - NP parts) during the luteal phase of the cycle (days 10-12 and 14-16) and two early stages of pregnancy (days 14-16 and 30-32).
Immunohistochemical studies using an antiserum against the mouse INSL5 peptide revealed INSL5-immunoreactive (irINSL5) neurons in the paraventricular, supraoptic, accessory secretory, and supraoptic retrochiasmatic nuclei and immunoreactive cell processes in the internal layer of the median eminence.
The present study suggests that NPY-ir neurons present in the infundibular nucleus can play a role in the preovulatory GnRH discharge from the median eminence..
The possible signaling pathway of ferutinin (1) in nervous tissue in vitro was assessed and the results showed that this compound is able to increase nitric oxide synthase activity and inositol monophosphate accumulation (49%, each) in the median eminence of the rat brain, suggesting that compound (1) is associated to the activation of phosphoinositide breakdown and nitric oxide production (NO), the last is a gaseous intercellular messenger known to play a broad role in human biology from homeostasis to pathology..
To investigate the anatomical basis of suggestions that TIP39 affects the secretion of several hypophysiotropic hormones we performed double-labeling studies and found that only somatostatin fibers contain PTH2R in the median eminence, which suggests that somatostatin release could be directly regulated via the PTH2R. However, several hypothalamic nuclei projecting to the median eminence contain a high density of both TIP39 and PTH2R fibers and terminals.
Following intravenous injection, OHSt was found in astrocytes of the median eminence and medial part of the arcuate nucleus whereas WGA intensely labelled the blood vessels and ependymal cells throughout the hypothalamus. In complete contrast, intracerebroventricular (icv) injection into the lateral ventricle resulted in OHSt uptake by ependymocytes and astrocytes in the area adjacent to the third ventricle, with virtually no uptake in regions taking up this dye following systematic injections, i.e., the median eminence and medial arcuate. The median eminence and medial arcuate take up molecules from the circulation, with different cell types taking up different molecules. Molecules in the CSF appear to be excluded from the median eminence and medial arcuate region..
Interestingly, the distribution of tuberomammillary hyperdipsia throughout the day was similar to that in non-lesioned animals, in contrast to the lack of rhythmicity observed in rats with anodic lesion to median eminence.
T+ males also had lower density of GnRH-immunolabelled fibers in the preoptic area and lower intensity of GnRH immunolabelling in the median eminence than C males, suggesting an inhibition of GnRH-I neuronal activity.
In drug-naive rats, acutely injected heroin significantly depleted NPFF-immunoreactive material within the neurons of the nucleus of solitary tract (NTS), significantly decreased the density of NPFF-immunoreactive nerve fibers within the median eminence, pituitary stalk, and neurohypophysis, and markedly increased NPY-immunoreactive neurons and nerve fibers in the thalamic paraventricular nucleus and bed nucleus of stria terminalis. In drug-sensitized rats, heroin significantly increased the number and immunostaining intensity of the NPFF-immunoreactive neurons within the NTS and induced minor changes in the NPFF-immunoreactive nerve fiber network of the median eminence, pituitary stalk, and neurohypophysis and a relatively minor increase in NPY neurons in the thalamic paraventricular nucleus and bed nucleus of stria terminalis.
Immunoreactive axons and axon terminals were also observed in the median eminence, suggesting that sst1 is also located pre-synaptically.
Associated changes in dopamine (DA) content in the anterior (AH), mediobasal (MBH) and posterior hypothalamus (PH) and median eminence (ME) were evaluated.
In the hypothalamus, intense staining was present in neurons of the supraoptic (SO), paraventricular (PVH), and accessory neurosecretory nuclei and in cell processes of median eminence.
Orexins and their receptors are expressed in the hypothalamic paraventricular nucleus and median eminence and orexin receptors in pituitary corticotropes, adrenal cortex, and medulla.
Hypothalamic and stalk median eminence contents of GnRH were not influenced (P> or =0.2) by fasting at any time period.
GnIH fibers are present in the median eminence (ME) and are in apparent contact with chicken GnRH (cGnRH)-I and -II neurons and fibers.
The study revealed that photoperiodic treatment, including the onset of photorefractoriness, had no significant effect on the size or number of GnRH-I, pro-GnRH-GAP or GnRH II immunoreactive cells, or the density of the GnRH-I, pro-GnRH-GAP immunoreactive fibres at the median eminence. GnRH-II was not found in the median eminence, suggesting that it does not regulate pituitary gonadotrophin secretion.
This work assesses the possible changes in gamma amino butyric acid (GABA) and taurine content in the hypothalamus, the median eminence and striatum after the exposure to various doses of cadmium. As far as the median eminence, 5 or 10 ppm of CdCl2 increased taurine concentration, and at a dose of 5 ppm enhanced GABA content.
In a previous study, we demonstrated seasonal morphological changes in the neuro-glial interaction between gonadotrophin-releasing hormone (GnRH) nerve terminals and glial endfeet in the median eminence (ME).
The hypothalamoneurohypophyseal system (HNS) consists of the large peptidergic magnocellular neurons of the supraoptic hypo thalamic nucleus (SON) and the paraventricular hypothalamic nucleus (PVN), the axons of which course through the internal zone of the median eminence and terminate at blood capillaries of the posterior lobe of the pituitary gland.
The objective of this study was to determine, in neonatal female rabbits after acute separation from the doe for 48 h, the changes in 24-h rhythms of plasma prolactin and median eminence and anterior pituitary concentration of dopamine (DA) and serotonin (5HT). In addition, median eminence concentration of the excitatory amino acid transmitters glutamate (GLU) and aspartate (ASP) and of the inhibitory amino acid transmitters gamma-aminobutyric acid (GABA) and taurine (TAU) was measured. Hemicircadian changes of median eminence DA were found in controls, whereas a single daily peak (at 17:00 h) was found in the separated pups. Plasma prolactin and median eminence DA correlated significantly and inversely in the control group only. Pup isolation decreased median eminence 5HT levels, augmented pituitary 5HT levels and disrupted their 24 h rhythmicity. Circulating prolactin correlated inversely with median eminence 5HT and directly with adenohypophysial 5HT only in controls. Isolation of pups generally modified the 24 h pattern of median eminence excitatory and inhibitory amino acid content by causing a prominent decrease at the beginning of the light phase.
Several areas, however, proved to be immunonegative: the central canal, the subcommissural organ, the ependymal zone of the median eminence in rat but its whole thickness in chicken, the subtrochlear organ, and the paraventricular organ. Presence of tight junctions coincides with the absence of aquaporin-4 in the ependyma of spinal cord, the subcommissural organ and the ependyma of median eminence..
Double-labelling immunofluorescence and confocal microscopy revealed that DORs are exclusively present in a subpopulation of GnRH nerve terminals, with the highest density in the external layer of the median eminence.
From the median basal hypothalamus, the median eminence releases gonadotrophin releasing hormone into the portal circulation to reach the anterior pituitary gland.
Thereafter, this induction occurs in the hypothalamic regions (such as the temperature-regulating centers), paraventricular nucleus (releasing and inhibiting hormone neurons), and the arcuate nucleus (a region containing these neurons and axons bound for the median eminence).
Within the hypothalamus, TACE is most abundantly expressed in astrocytes of the median eminence (ME), and its enzymatic activity increases selectively in this region at the time of the first preovulatory surge of gonadotropins.
An increasingly released AVP of magnocellular origin seems to provide a negative tonus on ACTH secretion most probably via inhibiting the release of ACTH secretagogues from the median eminence into hypophyseal portal blood..
The preoptic area has been implicated as a primary site of action of NMDA, while non-NMDA agonists have been suggested to act primarily at the arcuate/median eminence level.
AS-ODN injections differentially affected DA turnover in the axon terminals of the median eminence (ME), neural lobe (NL) and intermediate lobe (IL) of the pituitary gland, resulting in a significant decrease in DA release in the early subjective night in the ME (TIDA), a significant increase in DA release at the beginning of the day in the IL (PHDA), and no effect in the NL (THDA).
-
[ View All ]
