Distribution of calbindin, parvalbumin and calretinin in the lateral geniculate nucleus and superior colliculus in Cebus apella monkeys

Time course of dorsolateral geniculate nucleus plasticity in adult monkeys with laser-induced retinal lesions

We studied changes in the expression of growth-associated protein 43 (GAP43), glial fibrillary acidic protein (GFAP), and calcium-binding proteins (calbindin [Cb] and parvalbumin [Pv]) in the dorsal lateral geniculate nucleus (dLGN) of four capuchin monkeys with laser-induced retinal lesions. The lesions were generated with the aid of a neodymium-YAG dual-frequency laser with shots of different intensity and at different survival time in each animal. The expression of these proteins in the layers of the dLGN was evaluated by performing histodensitometry of coronal sections throughout the nucleus. High-power laser shots administered at the border of the optic disc (OD)-injured fibers resulted in large scotomas. These lesions produced a devastating effect on fibers in this passage, resulting in large deafferentation of the dLGN. The time course of plasticity expressed in this nucleus varied with the degree of the retinal lesion. Topographically, corresponding portions of the dLGN were inferred by the extent of the ocular dominance column revealed by cytochrome oxidase histochemistry in flattened preparations of V1. In the region representing the retinal lesion, the expression of GFAP, GAP43, Pv, and Cb increased and decreased in the corresponding dLGN layers shortly after lesion induction and returned to their original values with different time courses. Synaptogenesis (indicated by GAP43 expression) appeared to be increased in all layers, while "cleansing" of the glial-damaged region (indicated by GFAP expression) was markedly greater in the parvocellular layers, followed by the magnocellular layers. Schematic drawings of optic discs laser lesions and of series of coronal sections of the dLGN, in three monkeys, depicting the areas of the nucleus deafferented by the lesions.

Regional chemoarchitecture of the brain of lungfishes based on calbindin D-28K and calretinin immunohistochemistry

Lungfishes are the closest living relatives of land vertebrates, and their neuroanatomical organization is particularly relevant for deducing the neural traits that have been conserved, modified, or lost with the transition from fishes to land vertebrates. The immunohistochemical localization of calbindin (CB) and calretinin (CR) provides a powerful method for discerning segregated neuronal populations, fiber tracts, and neuropils and is here applied to the brains of Neoceratodus and Protopterus, representing the two extant orders of lungfishes. The results showed abundant cells containing these proteins in pallial and subpallial telencephalic regions, with particular distinct distribution in the basal ganglia, amygdaloid complex, and septum. Similarly, the distribution of CB and CR containing cells supports the division of the hypothalamus of lungfishes into neuromeric regions, as in tetrapods. The dense concentrations of CB and CR positive cells and fibers highlight the extent of the thalamus. As in other vertebrates, the optic tectum is characterized by numerous CB positive cells and fibers and smaller numbers of CR cells. The so-called cerebellar nucleus contains abundant CB and CR cells with long ascending axons, which raises the possibility that it could be homologized to the secondary gustatory nucleus of other vertebrates. The corpus of the cerebellum is devoid of CB and CR and cells positive for both proteins are found in the cerebellar auricles and the octavolateralis nuclei. Comparison with other vertebrates reveals that lungfishes share most of their features of calcium binding protein distribution with amphibians, particularly with salamanders.

Parvalbumin and GABA Microcircuits in the Mouse Superior Colliculus

The mammalian superior colliculus (SC) is a sensorimotor midbrain structure responsible for orienting behaviors. Although many SC features are known, details of its intrinsic microcircuits are lacking. We used transgenic mice expressing reporter genes in parvalbumin-positive (PV⁺) and gamma aminobutyric acid-positive (GABA⁺) neurons to test the hypothesis that PV⁺ neurons co-localize GABA and form inhibitory circuits within the SC. We found more PV⁺ neurons in the superficial compared to the intermediate SC, although a larger percentage of PV⁺ neurons co-expressed GABA in the latter. Unlike PV⁺ neurons, PV⁺/GABA⁺ neurons showed predominantly rapidly inactivating spiking patterns. Optogenetic activation of PV⁺ neurons revealed direct and feedforward GABAergic inhibitory synaptic responses, as well as excitatory glutamatergic synapses. We propose that PV⁺ neurons in the SC may be specialized for a variety of circuit functions within the SC rather than forming a homogeneous, GABAergic neuronal subtype as they appear to in other regions of the brain.

Architectonic characteristics of the visual thalamus and superior colliculus in titi monkeys

Titi monkeys are arboreal, diurnal New World monkeys whose ancestors were the first surviving branch of the New World radiation. In the current study, we use cytoarchitectonic and immunohistochemical characteristics to compare titi monkey subcortical structures associated with visual processing with those of other well-studied primates. Our goal was to appreciate features that are similar across all New World monkeys, and primates in general, versus those features that are unique to titi monkeys and other primate taxa. We examined tissue stained for Nissl substance, cytochrome oxidase (CO), acetylcholinesterase (AChE), calbindin (Cb), parvalbumin (Pv), and vesicular glutamate transporter 2 (VGLUT2) to characterize the superior colliculus, lateral geniculate nucleus, and visual pulvinar. This is the first study to characterize VGLUT2 in multiple subcortical structures of any New World monkey. Our results from tissue processed for VGLUT2, in combination with other histological stains, revealed distinct features of subcortical structures that are similar to other primates, but also some features that are slightly modified compared to other New World monkeys and other primates. These included subdivisions of the inferior pulvinar, sublamina within the stratum griseum superficiale (SGS) of the superior colliculus, and specific koniocellular layers within the lateral geniculate nucleus. Compared to other New World primates, many features of the subcortical structures that we examined in titi monkeys were most similar to those in owl monkeys and marmosets, with the lateral geniculate nucleus consisting of two main parvocellular layers and two magnocellular layers separated by interlaminar zones or koniocellular layers.

Distribution of calcium-binding proteins in the pigeon visual thalamic centers and related pretectal and mesencephalic nuclei. Phylogenetic and functional determinants

Multichannel processing of environmental information constitutes a fundamental basis of functioning of sensory systems in the vertebrate brain. Two distinct parallel visual systems - the tectofugal and thalamofugal exist in all amniotes. The vertebrate central nervous system contains high concentrations of intracellular calcium-binding proteins (CaBPrs) and each of them has a restricted expression pattern in different brain regions and specific neuronal subpopulations. This study aimed at describing the patterns of distribution of parvalbumin (PV) and calbindin (CB) in the visual thalamic and mesencephalic centers of the pigeon (Columba livia). We used a combination of immunohistochemistry and double labeling immunofluorescent technique. Structures studied included the thalamic relay centers involved in the tectofugal (nucleus rotundus, Rot) and thalamofugal (nucleus geniculatus lateralis, pars dorsalis, GLd) visual pathways as well as pretectal, mesencephalic, isthmic and thalamic structures inducing the driver and/or modulatory action to the visual processing. We showed that neither of these proteins was unique to the Rot or GLd. The Rot contained i) numerous PV-immunoreactive (ir) neurons and a dense neuropil, and ii) a few CB-ir neurons mostly located in the anterior dorsal part and associated with a light neuropil. These latter neurons partially overlapped with the former and some of them colocalized both proteins. The distinct subnuclei of the GLd were also characterized by different patterns of distribution of CaBPrs. Some (nucleus dorsolateralis anterior, pars magnocellularis, DLAmc; pars lateralis, DLL; pars rostrolateralis, DLAlr; nucleus lateralis anterior thalami, LA) contained both CB- and PV-ir neurons in different proportions with a predominance of the former in the DLAmc and DLL. The nucleus lateralis dorsalis of nuclei optici principalis thalami only contained PV-ir neurons and a neuropil similar to the interstitial pretectal/thalamic nuclei of the tectothalamic tract, nucleus pretectalis and thalamic reticular nucleus. The overlapping distribution of PV and CB immunoreactivity was typical for the pretectal nucleus lentiformis mesencephali and the nucleus ectomamillaris as well as for the visual isthmic nuclei. The findings are discussed in the light of the contributive role of the phylogenetic and functional factors determining the circuits׳ specificity of the different CaBPr types.

Parvalbumin-immunoreactive cells in the superior colliculus in dog: distribution, colocalization with GABA, and effect of monocular enucleation

Parvalbumin (PV) is thought to play a major role in buffering intracellular calcium. We studied the distribution, morphology of PV-immunoreactive (IR) cells, and the effect of enucleation on the PV distribution in the superior colliculus (SC) in dog (Canis familiaris) and compared PV labeling to that of calbindin D28K (CB) and GABA. These cells formed three laminar tiers in the dog SC; 1) the upper superficial gray layer (SGL), 2) the lower optic layer (OL) and the upper intermediate gray layer, and 3) the deep layer. The third tier was not very distinct when compared with the other two tiers. The distribution of PV-IR cells is thus complementary to that of CB-IR tiers. Our present data on the distribution of PV-IR cells within the superficial layers are strikingly different from those in previously studied mammals, which show PV-IR cells within the lower SGL and upper OL. However, there were no distinct differences in distribution within the deep layers compared with that of previously studied mammals. PV-IR cells in the SC varied dramatically in morphology and size, and included round/oval, vertical fusiform, stellate, horizontal and pyriform cells. Two-color immunofluorescence revealed quantitatively that 11.67% of the PV-IR cells colocalized with GABA. Monocular enucleation appeared to have no effect on the distribution of PV-IR cells in the contralateral SC. Similar to CB, these data suggest that retinal projection may not control the expression of PV in the dog SC. These results provide important information for delineating similarities and differences in the neurochemical architecture of the visual system.

Immunocytochemical Localization of Calbindin D28K, Calretinin, and Parvalbumin in Bat Superior Colliculus

The purpose of this study was to investigate the localization of cells containing the calcium-binding proteins (CBPs) calbindin D28K (CB), calretinin (CR), and parvalbumin (PV) in the superior colliculus (SC) of the bat using immunocytochemistry. CB-immunoreactive (IR) cells formed a laminar tier within the upper superficial gray layer (SGL), while CR-IR cells were widely distributed within the optic layer (OL). Scattered CR-IR cells were also found within the intermediate gray, white, and deep gray layers. By contrast, PV-IR cells formed a laminar tier within the lower SGL and upper OL. Scattered PV-IR cells were also found throughout the intermediate layers, but without a specific laminar pattern. The CBP-IR cells varied in size and morphology: While most of the CB-IR cells in the superficial layers were small round or oval cells, most CR-IR cells in the intermediate and deep layers were large stellate cells. By contrast, PV-IR cells were small to large in size and included round or oval, stellate, vertical fusiform, and horizontal cells. The average diameters of the CB-, CR-, and PV-IR cells were 11.59, 17.17, and 12.60 μm, respectively. Double-immunofluorescence revealed that the percentage of co-localization with GABA-IR cells was 0.0, 0.0, and 10.27% of CB-, CR-, and PV-IR cells, respectively. These results indicate that CBP distribution patterns in the bat SC are unique compared with other mammalian SCs, which suggest functional diversity of these proteins in visually guided behaviors.

Subcortical connections of area V4 in the macaque

Area V4 has numerous, topographically organized connections with multiple cortical areas, some of which are important for spatially organized visual processing, and others which seem important for spatial attention. Although the topographic organization of V4's connections with other cortical areas has been established, the detailed topography of its connections with subcortical areas is unclear. We therefore injected retrograde and anterograde tracers in different topographical regions of V4 in nine macaques to determine the organization of its subcortical connections. The injection sites included representations ranging from the fovea to far peripheral eccentricities in both the upper and lower visual fields. The topographically organized connections of V4 included bidirectional connections with four subdivisions of the pulvinar, two subdivisions of the claustrum, and the interlaminar portions of the lateral geniculate nucleus, and efferent projections to the superficial and intermediate layers of the superior colliculus, the thalamic reticular nucleus, and the caudate nucleus. All of these structures have a possible role in spatial attention. The nontopographic, or converging, connections included bidirectional connections with the lateral nucleus of the amygdala, afferent inputs from the dorsal raphe, median raphe, locus coeruleus, ventral tegmentum and nucleus basalis of Meynert, and efferent projections to the putamen. Any role of these structures in attention may be less spatially specific.

Subcortical projections of area V2 in the macaque

To investigate the subcortical efferent connections of visual area V2, we injected tritiated amino acids under electrophysiological control into 15 V2 sites in 14 macaques. The injection sites included the fovea representation as well as representations ranging from central to far peripheral eccentricities in both the upper and lower visual fields. The results indicated that V2 projects topographically to different portions of the inferior and lateral pulvinar and to the superficial and intermediate layers of the superior colliculus. Within the pulvinar, the V2 projections terminated in fields P1, P2, and P4, with the strongest projection being in P2. Central visual field injections in V2 labeled projection zones in P1 and P2, whereas peripheral field injections labeled P1, P2, and P4. No projections were found in P3. Both central and peripheral field injections in V2 projected topographically to the superficial and intermediate layers of the superior colliculus. Projections from V2 to the pulvinar and the superior colliculus constituted cortical-subcortical loops through which circuits serving spatial attention are activated.

Calcium binding protein expression in the optic tectum of Alligator during development

The onset and distribution of the calcium binding proteins, calretinin, calbindin, and parvalbumin, were examined in the optic tectum of Alligator mississipiensis embryos between Stages 18 and 26-28. The immunoreactivity of each calcium binding protein correlated well with the results from the Western blot experiments. In terms of onset and distribution, calretinin expressison was the most widespread of the three calcium binding proteins that were examined, and was also the earliest to be visualized. Calbindin expression occurred next, whereas parvalbumin expression was the most limited and appeared last. For small calretinin (+) neurons, the pattern of immunoreactivity during development was from inside to outside, whereas for the larger cells, it was from outside to inside. For calbindin immunoreactive cells in the superficial zone, the pattern was from outside to inside. The distribution of the parvalbumin immunopositive neurons did not change significantly over the time period examined. Similar data on other amniotes is limited. However, the pattern in Alligator shares some similarities with kittens in regards to the distribution of calbindin and parvalbumin in the developing superior colliculus.

Different distributions of calbindin and calretinin immunostaining across the medial and dorsal divisions of the mouse medial geniculate body

We studied the distributions of calretinin and calbindin immunoreactivity in subdivisions of the mouse medial geniculate body and the adjacent paralaminar nuclei. We found that the vast majority of labeled cells in the dorsal division of the medial geniculate body were immunoreactive for calbindin-only, whereas most of the remaining labeled cells were double-labeled. Very few calretinin+ only cells were observed. By contrast, we observed significant proportions of calbindin+ only, calretinin+ only and double-labeled cells in the medial division of the medial geniculate body. Further, the distributions of calbindin-only, calretinin-only and double-labeled cells did not differ between the medial division of the medial geniculate body, the suprageniculate nucleus, the peripeduncular nucleus and the posterior intralaminar nucleus. We found essentially no somatic staining for either calbindin or calretinin in the ventral division of the medial geniculate body. These data suggest that there are distinct neurochemical differences between the two non-lemniscal auditory thalamic nuclei. In addition, these data extend previous observations that the medial division of the medial geniculate body shares many properties with the paralaminar group of nuclei.

Calcium-binding protein calretinin immunoreactivity in the dog superior colliculus

We studied calretinin-immunoreactive (IR) fibers and cells in the canine superior colliculus (SC) and studied the distribution and effect of enucleation on the distribution of this protein. Localization of calretinin was immunocytochemically observed. A dense plexus of anti-­calretinin-IR fibers was found within the upper part of the superficial gray layer (SGL). Almost all of the labeled fibers were small in diameter with few varicosities. The intermediate and deep layers contained many calretinin-IR neurons. Labeled neurons within the intermediate gray layer (IGL) formed clusters in many sections. By contrast, labeled neurons in the deep gray layer (DGL) did not form clusters. Calretinin-IR neurons in the IGL and DGL varied in morphology and included round/oval, vertical fusiform, stellate, and horizontal neurons. Neurons with varicose dendrites were also labeled in the IGL. Most of the labeled neurons were small to medium in size. Monocular enucleation produced an almost complete reduction of calretinin-IR fibers in the SC contralateral to the enucleation. However, many calretinin-IR cells appeared in the contralateral superficial SC. Enucleation appeared to have no effect on the distribution of calretinin-IR neurons in the contralateral intermediate and deep layers of the SC. The calretinin-IR neurons in the superficial dog SC were heterogeneous small- to medium-sized neurons including round/oval, vertical fusiform, stellate, pyriform, and ­horizontal in shape. Two-color immunofluorescence revealed that no cells in the dog SC ­expressed both calretinin and GABA. Many horseradish peroxidase (HRP)-labeled retinal ganglion cells were seen after injections into the superficial layers. The vast majority of the double-labeled cells (HRP and calretinin) were small cells. The present results indicate that antibody to calretinin labels subpopulations of neurons in the dog SC, which do not express GABA. The results also suggest that the calretinin-IR afferents in the superficial layers of the dog SC originate from small class retinal ganglion cells. The expression of calretinin might be changed by the cellular activity of selective superficial collicular neurons. These results are valuable in delineating the basic neurochemical architecture of the dog visual system.

The superior colliculus of the camel: a neuronal-specific nuclear protein (NeuN) and neuropeptide study

In this study we examined the superior colliculus of the midbrain of the one-humped (dromedary) camel, Camelus dromedarius, using Nissl staining and anti-neuronal-specific nuclear protein (NeuN) immunohistochemistry for total neuronal population as well as for the enkephalins, somatostatin (SOM) and substance P (SP). It was found that, unlike in most mammals, the superior colliculus is much larger than the inferior colliculus. The superior colliculus is concerned with visual reflexes and the co-ordination of head, neck and eye movements, which are certainly of importance to this animal with large eyes, head and neck, and apparently good vision. The basic neuronal architecture and lamination of the superior colliculus are similar to that in other mammals. However, we describe for the first time an unusually large content of neurons in the superior colliculus with strong immunoreactivity for met-enkephalin, an endogenous opioid. We classified the majority of these neurons as small (perimeters of 40-50 microm), and localized diffusely throughout the superficial grey and stratum opticum. In addition, large pyramidal-like neurons with perimeters of 100 microm and above were present in the intermediate grey layer. Large unipolar cells were located immediately dorsal to the deep grey layer. By contrast, small neurons (perimeters of 40-50 microm) immunopositive to SOM and SP were located exclusively in the superficial grey layer. We propose that this system may be associated with a pain-inhibiting pathway that has been described from the periaqueductal grey matter, juxtaposing the deep layers of the superior colliculus, to the lower brainstem and spinal cord. Such pain inhibition could be important in relation to the camel's life in the harsh environment of its native deserts, often living in very high temperatures with no shade and a diet consisting largely of thorny branches.

Development of the human superior colliculus and the retinocollicular projection

We have used carbocyanine dye tracing from the brachium of the superior colliculus in conjunction with Nissl staining and immunohistochemistry to GAP-43 and calretinin to study the development of retinal projections to the superior colliculus in 17 human embryos and fetuses aged from 8 to 28 weeks. Lamination of the superior colliculus begins to emerge by 11 weeks, and by 16 weeks all seven layers of the mature superior colliculus are visible. Fibres immunoreactive to GAP-43 were seen at 13 weeks in the most superficial layers. By 19 weeks, GAP-43 immunoreactivity was present in the stratum opticum as well as the deeper fibres layers, indicating the development of fibre pathways following those laminae. Carbocyanine dye tracing of retinocollicular projections showed extensive rostrocaudally running unbranched fibres in the superficial superior colliculus at 12 weeks. Shortly after this (13 weeks), retinocollicular fibres penetrate the deeper collicular layers and branching becomes apparent. We also saw occasional retrogradely labelled somata following DiI insertion into the superior brachium. Our findings indicate that development of the human superior colliculus and its connections is largely complete by 20 weeks. This would suggest that functional capacity of the human superior colliculus should also be mature by the middle of gestation.

Visually-induced NGFI-A protein expression in the calbindin-, parvalbumin- and nitric oxide synthase-neuronal populations of the rat superior colliculus

The expression of the immediate early gene NGFI-A in the nervous system is induced by sensory stimulation and seems to be related to long-term synaptic plasticity. We have used double-labeling immunohistochemistry to identify calbindin (CB)(+), parvalbumin (PV)(+) and neuronal nitric oxide synthase (nNOS)(+) neurons that also expressed the protein encoded by this immediate early gene after light-exposure on in the superficial layers of the rat superior colliculus (sSC). The majority of the NGFI-A(+) cells were not double-labeled for the tested markers. In the stratum zonale+stratum griseum superficiale (SZ/SGS), only 17.8%, 8.0% and 12.1% of NGFI-A(+) cells were also labeled for CB, PV or nNOS, respectively. In the stratum opticum (SO), only 10.5% of the NGFI-A(+) cells were also CB(+). Furthermore, only a small subset of each population expressed the NGFI-A protein after light-exposure. In the SZ/SGS, 35.7% of the CB(+), 32.1% of the PV(+) and 26.6% of the nNOS(+) neurons also expressed the NGFI-A. In the SO, 31.7% of the CB(+) neurons also expressed the NGFI-A. The proportional distribution of the nNOS(+)/NGFI-A(+) neurons throughout the SZ/SGS layers showed a slight but significant rostro-caudal gradient. No significant difference was observed for the other markers, indicating homogeneous activation of these populations throughout the retinotopic map. Our results suggest that the visually-driven NGFI-A expression is not restricted to a specific population of the sSC and that visual processing in this structure, as assessed by the expression of this candidate-plasticity protein, involves the activation of subsets of ascending and non-ascending projection neurons.

Distribution of NADPH-diaphorase in the superior colliculus of Cebus monkeys, and co-localization with calcium-binding proteins

We examined the distribution of the enzyme dihydronicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the superior colliculus (SC) of the New World monkey Cebus apella, and the co-localization of this enzyme with the calcium-binding proteins (CaBPs) calbindin-D28K, parvalbumin and calretinin. Despite the intensely labeled neuropil, rare NADPH-d-positive cells were observed in the stratum griseum superficiale (SGS). Most of the labeled cells in the SC were found in the intermediate layers, with a great number also in the deeper layers. This pattern is very similar to that described in the opossum (Didelphis marsupialis) and in the cat, and different from the pattern found in the rat, which shows labeled cells mainly in the SGS. Cells doubly stained for NADPH-d and CaBPs were observed throughout the SC, although in a small number. Of the NADPH-d-positive cells, 20.3% were doubly labeled for NADPH-d and parvalbumin, 10.2% revealed co-localization with calretinin, and 5.6% with calbindin. The low number of double-stained cells for NADPH-d and the CaBPs indicates that these molecules must participate in different functional circuits within the SC.

Calretinin expression in odontogenic cysts

Calretinin is a calcium-binding protein with a possible role as a calcium buffer, calcium-sensor, or regulator of apoptosis. Calretinin is expressed in neural tissue, is a specific marker of mesothelial cells, and has been demonstrated in the odontogenic epithelium during odontogenesis in rat molar tooth germs. Moreover, it has been found to be expressed in a high proportion of solid, unicystic, and multicystic ameloblastomas, whereas, on the contrary, no positive staining has been found in odontogenic keratocysts, residual cysts, and dentigerous cysts. The purpose of this study was to evaluate calretinin expression in radicular cysts, follicular cysts, orthokeratinized keratocysts, and parakeratinized keratocysts. A total of 70 odontogenic cysts, 24 radicular cysts, 24 follicular cysts, and 22 odontogenic keratocysts (10 orthokeratinized keratocysts, 12 parakeratinized keratocysts) were evaluated. All the radicular cysts, follicular cysts, and orthokeratinized keratocysts were negative. However in 8 of 12 parakeratinized keratocysts, there was a positivity to calretinin in the parabasal-intermediate layers of the cyst epithelium. This positivity to calretinin in the parabasal layers in parakeratinized keratocysts, similar to that found for other markers like PCNA and p53, could point to an abnormal control of the cell cycle and could help to explain the differences in the clinical and pathologic behavior of odontogenic keratocysts, in particular the differences found between orthokeratinized keratocysts and parakeratinized keratocysts.

Laminar expression of neurofilament protein in the superior colliculus of the marmoset monkey (Callithrix jacchus)

The expression profile of the monoclonal antibody SMI-32 was examined in the superior colliculus of adult marmosets. This antibody recognises subunits of the non- and dephosphorylated neurofilament protein, labelling predominantly neuronal perikarya and dendrites. The densest cellular label was observed in the intermediate layers (primarily, the stratum griseum intermediale), consisting of large multi- or bipolar neurones which were preferentially located within cytochrome oxidase-rich regions. The morphological characteristics of neurones showing heavy staining resemble those of extrinsic projection cells, suggesting a correlation between neurofilament content and axonal length.

Neurofilament protein expression in the geniculostriate pathway of a New World monkey ( Callithrix jacchus)

We examined the expression profile of non-phosphorylated neurofilament protein in the dorsal lateral geniculate nucleus (LGN) and striate cortex (V1) of a New World simian, the marmoset monkey, using the monoclonal antibody SMI-32. The overall distribution of neurofilament protein in the marmoset resembled that previously described in Old World monkeys. While immunostained neurones were observed throughout the LGN, there were clear laminar differences in terms of both cellular and neuropil labelling. Neurones in the magnocellular layer cells stained more densely than those in the parvocellular layers. The marmoset's well-defined koniocellular layers showed an overall light stain of both neurones and neuropil. In V1, densely stained pyramidal cells and heavy neuropil label were observed in the two sublayers that send projections to the middle temporal area (MT): a supragranular band located in layer 3C (Brodmann's layer 4B) and an infragranular band located near the top of layer 6. More lightly stained, small pyramidal cells were also found in layer 3Balpha. Accordingly, in both New World and Old World monkeys the expression of neurofilament protein is correlated with specific functional subdivisions of the geniculocortical pathway. In particular, projection neurones associated with fast-conducting pathways to the extrastriate 'dorsal stream' appear to contain higher levels of this protein.

Chemoarchitecture of GABAergic neurons in the ferret superior colliculus

gamma-Aminobutyric acid (GABA)ergic neurons are thought to play a key role both in visual processing and in the complex sensory-motor transformations that take place in the mammalian superior colliculus. To understand the organization of GABAergic neurons in the ferret superior colliculus, we applied antisera to several markers of GABAergic function, including GABA, two isoforms of its synthetic enzyme glutamic acid decarboxylase (GAD-65 and GAD-67), and the GABA transporter, GAT-1. We also applied antisera to several calcium binding proteins (calbindin [CB], calretinin [CR], and parvalbumin [PV]) and neuronal nitric oxide synthase (NOS), chemical markers that colocalize with GABA in some areas of the central nervous system. The distribution of GABAergic neurons in the ferret is similar to that of other mammalian species. GABAergic neurons in the ferret superior colliculus were small, morphologically diverse, and widely distributed throughout all layers of the colliculus. As has been shown in other mammalian species, neurons expressing PV, CB, CR, and NOS were differentially distributed in layers and patches throughout the ferret colliculus. None of these markers, however, showed a distribution that mirrored that of GABAergic neurons. Furthermore, few GABAergic neurons colocalized these neurochemical markers. Only 14% of GABAergic neurons in the superficial layers and 18% of neurons in the deeper layers colocalized PV, 14% of GABAergic neurons in the superficial layers and 10% in the deeper layers colocalized CB, and only 1% of GABAergic neurons in both the superficial and deep layers colocalized nitric oxide synthase. Thus, the arrangement of GABAergic neurons in the ferret superior colliculus is broadly distributed and is distinct from other recognized organizational patterns in the superior colliculus.

Changes of calretinin, calbindin D28K and parvalbumin-immunoreactive neurons in the superficial layers of the hamster superior colliculus following monocular enucleation

We studied the effects of monocular enucleation on the patterned distribution of calretinin-, calbindin D28K- and parvalbumin-immunoreactive (IR) neurons in the superficial layers of the hamster superior colliculus (SC). The calcium-binding proteins were localized using antibody immunocytochemistry. Almost complete depletion of the calretinin-IR fibers in the superficial layers of the contralateral SC was found following unilateral enucleation. Quantitative analysis showed that on the experimental side of the SC, an enormous number of calretinin-IR cells newly appeared (716%). On the experimental side of the SC, the number of parvalbumin-IR cells also increased (32%). By contrast, on the experimental side of the SC, the number of calbindin D28K-IR cells exhibited a reduction (43%). Two-color immunofluorescence revealed that none of the newly appeared calretinin-IR cells were labeled with antibodies to calbindin D28K or parvalbumin. The present results demonstrate that retinal projection may control the activity of the expression of these calcium-binding proteins in the hamster SC but in different manners. The results also show that the patterned change of calretinin and parvalbumin in the hamster SC is comparable with other animals, but the change of calbindin D28K is not identical.