The posterior pretectal nucleus and the parvocellular superficial pretectal nucleus receive afferents from the ipsilateral nucleus isthmi. The posterior pretectal nucleus projects to the inferior hypothalamic lobe. 
Although only a small change of VGluT2 immunoreactivity was observed in the contra- and ipsilateral suprachiasmatic nuclei, olivary pretectal nucleus, anterior pretectal nucleus, and posterior pretectal nucleus, moderate reduction of VGluT2 was found in these regions after bilateral enucleation.
Accordingly, the 'nucleus lentiformis' (which contains numerous NPY cells) corresponds to the nucleus of the optic tract, the 'nucleus sublentiformis' (containing a dense network of NPY fibres) to the posterior pretectal nucleus, and the 'nucleus of the pretectal area' corresponds to the medial pretectal nucleus.
Enzymatic removal of CSs by chondroitinase ABC after optic nerve crush significantly increased the number of animals showing erroneous growth of optic axons into the nonretinorecipient magnocellular superficial/posterior pretectal nucleus (83% vs 42% in controls).
The highest density of clock transcripts was observed in the periventricular layer (SPV) of the optic tectum, but a weaker expression was detected in some pretectal nuclei, such as the posterior pretectal nucleus (PO) and the periventricular regions of the diencephalon.
Also, the posterior pretectal nucleus which is absent in Polypterus but which has been identified as a small nucleus both in Lepisosteus and Amia is represented in Acipenser by a small group of scattered cells..
The pretectal area contained degenerated fibers which were widespread in (i) the nucleus of the optic tract, (ii) olivary pretectal nucleus, (iii) anterior pretectal nucleus, and (iv) the posterior pretectal nucleus.
The posterior pretectal nucleus and nucleus of the optic tract may also project to the zona incerta.
Three regions were found to evoke the accommodation response: the posterolateral pretectum, including the nucleus of the optic tract and the posterior pretectal nucleus; the posteromedial pretectum, including the nucleus of the posterior commissure (NPC) and adjacent commissural fibers; and the MRF area dorsolateral to the oculomotor nucleus.
All recorded neurons were located in the nucleus of the optic tract and in the posterior pretectal nucleus.
Pretectal cells afferent to the LGNd were located in the nucleus of the optic tract (NOT), adjacent dorsal terminal nucleus of the accessory optic system (DTN), and posterior pretectal nucleus (NPP).
Following the injection of biocytin, in the ascending projections, labeled terminals were seen mainly in the caudal portion of the nucleus of the optic tract, the nucleus of the posterior commissure, the posterior pretectal nucleus, the olivary pretectal nucleus, the mesencephalic reticular formation at the level of the oculomotor nucleus, and the lateral posterior nucleus of the thalamus on the ipsilateral side. Following the injection of muscimol into the pretectum, including the nucleus of the optic tract, the posterior pretectal nucleus, and the nucleus of the posterior commissure, accommodative responses evoked by microstimulation of the superior colliculus were reduced to 33-55% of the value before the injections. These findings suggest that the accommodation area in the superior colliculus projects to the oculomotor nucleus through the ipsilateral pretectal area, especially the nucleus of the optic tract, the nucleus of posterior commissure, and the posterior pretectal nucleus, and also projects to the pupilloconstriction area (the olivary pretectal nucleus), the vergence-related area (the mesencephalic reticular formation), and the active visual fixation-related area (the nucleus raphe interpositus)..
The posterior pretectal nucleus received sparse projections from area 7 and the cortex lining the intraparietal sulcus (dorsomedial part of area 19 and POa).
In the same cases, many cell bodies containing HRP reaction product also were found 1) ipsilaterally in the motor cortex, anterior pretectal nucleus, and a restricted area of the caudal part of the substantia nigra pars reticulata; 2) contralaterally in the anterior and posterior interposed cerebellar nuclei as well as in a portion of the lateral cerebellar nucleus; and 3) bilaterally in the zona incerta, the posterior pretectal nucleus, the pedunculopontine tegmental nuclei, the spinal trigeminal nucleus, the dorsal column nuclei, and the spinal cord.
Furthermore, projections are traced to the ipsilateral brainstem, including two areas of the pretectal complex: (1) one in the NOT, extending in some cases to the adjacent lateral portion of the posterior pretectal nucleus (PPN), and (2) one in the pars compacta of the anterior pretectal nucleus (APNc).
There have been conflicting reports on the chemical nature of the projection of the pretectal nuclei [ nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract (NOT-DTN complex) and posterior pretectal nucleus] to the lateral geniculate nucleus and inferior olive. We were able to demonstrate glutamic acid decarboxylase mRNA expression in up to 70% of lateral geniculate nucleus-projecting NOT-DTN and posterior pretectal nucleus neurons but in none of the pretecto-olivary projection neurons.
Four nuclei of the pretectal complex, the olivary pretectal nucleus, the medial pretectal nucleus, the nucleus of the optic tract and the posterior pretectal nucleus, all have a demonstrated role in visual function.
Following monocular injection of either horseradish peroxidase or rhodamine-B-isothiocyanate, four pretectal nuclei, including the nucleus of the optic tract, posterior pretectal nucleus, anterior pretectal nucleus and the olivary pretectal nucleus, could be identified to receive direct retinal input in both pigmented and albino strains.
Apomorphic features include the presence of a single, large, circular lamina that surrounds a central neuropil in all but the most caudal part of nucleus anterior, a lack of bilateral asymmetry in the habenular nuclei, the relatively small size of the periventricular nucleus of the posterior tuberculum, the presence of two, distinguishable caudomedial nuclei in the posterior tuberculum, elongation and folding of the neuropil of nucleus pretectalis superficialis pars parvicellularis, and the relatively large size of nucleus pretectalis superficialis pars magnocellularis and the posterior pretectal nucleus..
Compared to non-stimulated control rats or rats in which EA was applied to a non-acupuncture point, both 4-Hz and 100-Hz EA-treated groups exhibited a significantly greater number of Fos-labeled neurons in the dorsal horn of the L2 spinal cord segment, lateral parabrachial nucleus, substantia nigra, nucleus raphe pallidus, dorsal raphe, locus coeruleus, posterior pretectal nucleus, and the lateroventral periaqueductal gray.
The posterior pretectal nucleus, previously identified in teleosts and in the bowfin Amia, is also present in gars. The small size of the posterior pretectal nucleus in gars supports the hypothesis that this nucleus was small plesiomorphically. The superficial pretectal nuclei, including the posterior pretectal nucleus, are strongly positive for AChE.
Single neurons in the pretectal nucleus of the optic tract and posterior pretectal nucleus were extracellularly recorded in anaesthetized cats and tested for antidromic activation after electrical stimulation of the ipsilateral dorsal lateral geniculate nucleus.
Of particular note, a posterior pretectal nucleus and, possibly, a homologue of nucleus corticalis were found to be present in the pretectum. The posterior pretectal nucleus is relatively small in the bowfin, and the distribution of a small, versus a large, posterior pretectal nucleus in Teleostei and Halecomorphi suggests that this nucleus was small plesiomorphically.
Another important difference between axons that project to GLd layers 3 and 6 is that those that project to layer 6 give off collaterals to the posterior pretectal nucleus, whereas at least some axons that project to layer 3 send a collateral to the ventral lateral geniculate nucleus (GLv).
The posterior pretectal nucleus, which in Osteoglossum receives second order visual input and projects to the inferior lobe of the hypothalamus, was identified and characterized in species from all major groups of non-neoteleost teleosts. The hypothesis that the posterior pretectal nucleus in these species is homologous to both the pars intermedius of the superficial pretectal nucleus and nucleus glomerulosus in acanthopterygians is supported by multiple similarities in relative position and cytoarchitecture. Nucleus corticalis, which receives retinal input and projects to the posterior pretectal nucleus (or to nucleus glomerulosus), was identified in species belonging to three of the four major teleost radiations. Both the posterior pretectal nucleus and nucleus corticalis are plesiomorphic for teleosts. The presence of glomeruli in the posterior pretectal nucleus and nucleus glomerulosus in esocids and acanthopterygians, respectively, and the presence of two nuclei, the pars intermedius and nucleus glomerulosus, in acanthopterygians, as opposed to one nucleus, the posterior pretectal nucleus, are apomorphies..
In both types of injection we found labeled pretectal cells mainly in the nucleus of the optic tract but also found some cells labeled in the olivary pretectal nucleus and the posterior pretectal nucleus.
It is demonstrated that AChE is a highly selective and reliable interspecific marker for all divisions of the superficial pretectum, the nucleus corticalis, the posterior pretectal nucleus (or nucleus glomerulosus) and portions of the inferior lobe.
Neurons in the superior colliculus were found to be arranged in a mediolateral array that corresponds to the rostromedial to caudolateral array of their axon projections to the nucleus of the optic tract and posterior pretectal nucleus.
Smaller and sparser collections of stained cell bodies could be found in the ventromedial hypothalamus, the posterior pretectal nucleus, the nucleus of the posterior commissure, the peripeduncular nucleus, the periaqueductal central gray, the contralateral anterior pretectal nucleus, and the locus coeruleus.
These neurons are composed of fusiform cells and small-sized multipolar cells in the olivary pretectal nucleus, superficial horizontal cells, fusiform cells, small-, medium- and large-sized multipolar cells in the optic tract nucleus, and small- and medium-sized multipolar cells in the posterior pretectal nucleus.
In the pretectum, the projections to the rostral pretectal areas were greatly increased in area, especially in the region of the olivary pretectal nucleus and posterior pretectal nucleus.
(1) Injection of tracer into the spinal enlargements resulted in dense terminal labeling in the parabrachial nucleus (PBN) and the periaqueductal gray matter (PAG); moderate termination was observed in the intercollicular nucleus (Inc), the intermediate and deep gray layers of the superior colliculus (SGI, SGP), the posterior pretectal nucleus (PTP), and the nucleus of Darkschewitsch (D); and scattered terminal fibers were seen in the cuneiform nucleus (CNF) and the pars compacta of the anterior pretectal nucleus (PTAc).
The lateral part of the nucleus of the optic tract (NTO) receives afferents from the superior retina, and the medial part of NTO and posterior pretectal nucleus (NPP) receives afferents from the inferior retina.
In some areas dendrites extended into the neuropil of the adjacent dorsal terminal nucleus of the accessory optic system and the posterior pretectal nucleus.
In wild-type mice, strong contralateral retinal projections covered the entire nucleus of the optic tract, the anterior and posterior divisions of the olivary pretectal nucleus, and the posterior pretectal nucleus. The pattern of contralateral retinal projection to the nucleus of the optic tract and posterior pretectal nucleus in mutants was indistinguishable from that seen in the normal wild-type mice.
Pretectal neurons were HRP-labeled primarily in the contralateral medial pretectal nucleus with a smaller number in the ipsilateral posterior pretectal nucleus.
Minor projections to the intercollicular nucleus, posterior pretectal nucleus and nucleus of Darkschewitsch were found.
Area 7a projects to none of these structures, but it does project to the posterior pretectal nucleus.
The posterior pretectal nucleus (PP) is composed predominantly of (1) multipolar cells with horizontally and vertically oriented dendrites extending out transverse to the optic axons; (2) piriform cells with dendrites extending dorsally toward the brachium; and (3) small multipolar neurons.
In both species the retinal projection terminated bilaterally in the suprachiasmatic, dorsal lateral geniculate, ventral lateral geniculate, and pretectal olivary nuclei and contralaterally in the posterior pretectal nucleus, superficial gray layers of the superior colliculus, and nuclei of the accessory optic system.
All luminance detectors were located in the olivary pretectal nucleus, whereas darkness detectors were located in the posterior pretectal nucleus. The olivary pretectal nucleus may therefore be involved in pupilloconstruction in the light, and the posterior pretectal nucleus, with pupillodilation in the dark..
In the posterior pretectal nucleus their target areas were smaller and located more ventromedially.
After injections of HRP into the olive in six cats, cells were labeled ipsilaterally in the anterior pretectal nucleus (NPA), the posterior pretectal nucleus (NPP), the nucleus of the optic tract (NOT), and the dorsal terminal nucleus of the accessory optic tract (DTN).
The main terminal areas were the periaqueductal gray matter, the intercollicular nucleus, the posterior pretectal nucleus and the nucleus of Darkschewitsch.
Labelled cells were identified in a variety of structures, including the nucleus of the optic tract (NOT), the posterior pretectal nucleus (NPP), the superior colliculus (SC), the parabigeminal nucleus (PBN), the midbrain reticular formation (MRF), locus coeruleus and nucleus sub-coeruleus, the substantia nigra (SN), and parts of the raphe complex.
The results show large projections to the lateral and ventrolateral parts of the periaqueductal gray (PAG1), the posterior pretectal nucleus (PP) and the nucleus of Darkschewitsch (D).
Fairly dense terminal networks are found in the posterior pretectal nucleus (PP) and the compact part of the anterior pretectal nucleus (PAc) as well.
On the contralateral side terminal labeling was found in both pigmented and albino rabbits in the nucleus of the optic tract (NOT), the anterior pretectal nucleus (PA), the posterior pretectal nucleus (PP) and the pretectal olivary nucleus (PO).
By embryonic day 56, five distinct bilateral fields of retinal fiber termination are apparent within the following regions: (i) the nucleus of the optic tract; (ii) the pretectal olivary nucleus; (iii) the posterior pretectal nucleus; (iv) the anterior pretectal nucleus; and (v) the medial pretectal nucleus.
When the injections were placed in the lateral part of the motor area of the hand or arm regions, silver grains were manifested in the nucleus of Darkschewitsch (ND) in its whole rostrocaudal extent, and they were observed also in the ventrolateral part of the anterior pretectal nucleus (PA) and in the caudal portion of the posterior pretectal nucleus (PP).
In addition, the parvocellular division of the red nucleus and the posterior pretectal nucleus contained large numbers of cells when the injection spread into the inferior olive.
In the midbrain the periaqueductal gray, the nucleus of Darkschewitsch and the posterior pretectal nucleus contained fairly dense labeling.
Injections in LD result in retrogradely labeled neurons in all nuclei of the pretectal complex, including the nucleus of the optic tract (NTO), the posterior pretectal nucleus (NPP), the anterior pretectal nucleus (NPA), the pretectal olivary nucleus (NOL), and the medial pretectal nucleus (NPM).
In the pretectum, the DN fibers terminated ventrally in the reticular part of the anterior pretectal nucleus and the posterior pretectal nucleus. THe AIN fibers terminated ventrally in the compact part of the anterior pretectal nucleus and the posterior pretectal nucleus.
The greatest concentration of radioactivity within each optic center was found in the visuotopic aspect subserving the superior visual field; particularly the medial aspects of the superior colliculus, olivary pretectal nucleus, and posterior pretectal nucleus, and the anterior portion of the nucleus of the optic tract.
A caudal field is located within the sub-brachial nucleus of the optic tract, located between the brachium of the superior colliculus and the posterior pretectal nucleus.
Areas 19 and LS project also the contralateral pretectal nuclei, mainly to the posterior pretectal nucleus.
Labelled cells were only found in the posterior pretectal nucleus (NPP), the nucleus of the optic tract (NOT) and the anterior pretectal nucleus (NPA).
The endings of retinal axons form three terminal fields in the pretectum in: 1, olivary pretectal nucleus (PO), bilaterally; 2, posterior pretectal nucleus (PP), bilaterally; and 3, nucleus of the optic tract (NTO), contralaterally.
Injection of HRP into the caudal dorsal accessory olive resulted in dense neuronal labelling in the ipsilateral caudal pole of the posterior pretectal nucleus (PPN).
Visual structures: ventral lateral geniculate nucleus, parabigeminal nucleus, pretectal area (nucleus of the optic tract, posterior pretectal nucleus, nuclei of the posterior commissure). Evidence is presented that only the parabigeminal nucleus, the nucleus of the optic tract, and the posterior pretectal nucleus project to the superficial collicular layers (striatum griseum superficiale and stratum opticum), while all other afferents terminate in the deeper layers of the colliculus.
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