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Axonal branching in the periaqueductal gray projections to the thalamus: a fluorescent retrograde double-labelling study
No full textTopography and receptive field organization of the body midline representation in the ventrobasal complex of the cat
No full textLaminar pattern of termination of the ipsilateral cortical projection from SII to SI in cats
No full textThe present light and electron microscopic experiments were carried out on the first somatic sensory area (SI) of cats to deternine the laminat distribution of axon terminals from the ipsilateral secon somatic sensory area (SII) and to identify the types of synapses between these terminals and neuronal elements of SI. Phaseolus vulgari leucoagglutinin (PHA-L) was iontophoretically injected into multiple sites and at different cortical dephts of the forepaw representation zone of SII. Fixed brain blocks containing the injected SII and ipsilateral SI were cut into slices and processed immunocytochemically to stain PHA-L-filled fibers and terminals. Light microscopic examination of SI revealed patches of anterograde labeling in the forepaw representation zone, concentrated mainly in supragranular layers. In these layers, thin immunolabelled fibers branched extensively and formed a dense plexus that was more prominent in layers II and I. Conversely, the infragranular layers contained fragments of vertically oriented thick fibers that rarely emitted axon collaterals. PHA-L-labeled axons had numerous swellings along their course, interpreted as boutons an passant, and stalked boutons. Of 19,661 labeled terminals ( 17,833 beads and 1,828 stalked boutons), 84.74% were observed in supragranular layers, with the highest concentration in layer II (33.15%) and lower in layers I (26.27%) and III (25.30%). The proportion of terminals was lower in layer IV (6.49%) and V (5.45%) and lowest in layer VI (3.32%). These counts also showed that boutons en passant were the majority (90.70%) and stalked boutons, the minority (9.30%). The ratio of these two types of presynaptic specializations was similar (9:1) in all six layers.
Electron microscopic examination of the labeled region of SI showed that both axon swellings and stalked boutons formed synapses of the asymmetric type with SI neuronal elements. The majority (85.37%) of a sample of 130 labeled terminals synapsed on SI neurons in layers I-III. The identified possynaptic profiles were dendritic spines (61.11%) or medium-sized and small dendrites (38.89%). These results are discussed in relation to those of a companion study on the laminar pattern of the projection from SI to SII of cats. Based on the anatomical organization of these reciprocal connections, there seems to be no clear hierarchical relationship between SI and SII in cats
Thalamic connections of the second somatic sensory area in cats studied with anterograde and retrograde tract-tracing techniques.
No full textCytochrome oxidase histochemistry reveals regional subdivisions in the rat periaqueductal gray matter
No full textPostnatal development of high-affinity plasma membrane GABA transporters GAT-2 and GAT-3 in the rat cerebral cortex
No full textWe investigated the developmental profile of plasma membrane γ-aminobutyric acid (GABA) transporters (GATs) GAT-2 and GAT-3 expression by immunocytochemistry with affinity-purified polyclonal antibodies in the rat neocortex. At all developmental ages investigated, GAT-2 ir was prominent in the arachnoid and in the trabeculae of the subarachnoid space, whereas it was weak within the cortical parenchyma; the adult pattern was reached during the third week of postnatal life. GAT-3 ir was present at birth and increased rapidly in the first week, when numerous positive cells were present throughout the cortical layers; at P10, GAT-3-positive cells became less numerous and GAT-3 ir switched to the adult pattern, which was expressed at P20. Confocal and electron microscopic investigations showed that GAT-3 positive cells were both neurons and astrocytes. The present evidence indicates that early in development GAT-3 is abundantly expressed in the cerebral cortex, where its expression appears to correlate with developmental variations in GABA levels, and suggests that it accounts for the largest fraction of GABA transport observed in the neonatal cerebral cortex
GABA transporter-1 (GAT-1) immunoreactivity in the cat periaqueductal gray matter
No full textUsing light- and electron-microscopic immunocytochemistry, we investigated the regional distribution and the ultrastructural localization of GAT-1, a prominent GABA transporter, in the cat PAG. Light microscopic observations indicate that GAT-1-immunoreactive elements are particularly dense in PAG-DL and form a pair of longitudinal columns extending in the intermediate region of this structure. At electron-microscopic level, GAT-1 immunoreactivity was present in axon terminals forming symmetric synapses and in the distal processes of astroglial cells. These data further confirm the existence of longitudinal columns within PAG. They also indicate that GAT-1 could influence the action of GABA on its receptors, probably regulating the magnitude and duration of GABA's synaptic action on PAG neurons, and suggest that astrocytes may play an important role in this process
Gamma-aminobutyric acid transporters in the cat periaqueductal gray: a light and electron microscopic immunocytochemical study
No full textThe γ-aminobutyric acid (GABA) plasma membrane transporters (GATs) mediate GABA uptake into presynaptic axon terminals and glial processes, thus contributing to the regulation of the magnitude and duration of the action of GABA at the synaptic cleft. The aim of the present study was to investigate the expression of three high-affinity GABA transporters (GAT-1, GAT-2, and GAT-3) in the periaqueductal gray matter (PAG) of adult cats by using immunocytochemistry with affinity-purified antibodies. Light microscopic observations revealed GAT-1 immunoreactivity in punctate structures, particularly dense in the lateral portion of the dorsolateral PAG column. Weak GAT-2-immunopositive puncta were homogeneously distributed in the PAG. GAT-3 immunoreactivity was detected in each column of the PAG but was more intense in the dorsolateral PAG column and around the aqueduct. Electron microscopic studies showed GAT-1 immunoreactivity in distal astroglial processes, in unmyelinated and small myelinated axons, and in axon terminals making symmetric synapses on both PAG neurons and dendrites. GAT-2 immunoreactivity was present mostly in the form of patches of different sizes in the cytoplasm of neuronal elements like the perikarya and dendrites of PAG neurons, in myelinated and unmyelinated axons, and in the axon terminals forming both symmetric and asymmetric synapses. Labeling was also observed in nonneuronal elements. Astrocytic cell bodies and their distal processes as well as the ependymal cells lining the wall of the aqueduct showed patches of GAT-2 immunoreactivity. Electron microscopic observation revealed GAT-3 immunoreactivity exclusively in distal astrocytic processes adjacent to the somata of PAG neurons and in axon terminals making both symmetric and asymmetric synapses. The present results suggest that three types of termination systems of GABAergic transmission are present in the cat periaqueductal gray matter
Postnatal development of high-affinity plasma membrane GABA transporters GAT-2 and GAT-3 in the rat cerebral cortex
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