Soc. Neurosci. Abstr. 1997.10

DISTRIBUTION OF AMPA-TYPE GLUTAMATE RECEPTORS ALONG THE VENTRAL VISUAL CORTICAL PATHWAY IN THE MACAQUE: A GRADIENT REFLECTING THE CORTICAL HIERARCHY.

L.H. Xu, H. Tanigawa and I. Fujita*. Dept. Cognitive Neurosci., Osaka Univ. Med. Sch., Suita, Osaka 565, Japan

Glutamate receptors play a crucial role in information transmission through thalamocortical and corticortical pathways. An immuno-histochemical analysis with subtype-specific antibodies was conducted for determination of the distribution of ionotropic, a-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid (AMPA)-type glutamate receptors (GluRs 1-4) along the ventral visual cortical pathway in Japanese monkeys (Macaca fuscata).
Each subtype showed cellular, laminar and regional distribution patterns different from those of the others. An antibody against GluR1 moderately stained a group of neurons, most of which were of nonpyramidal types and were found in layers 2, 5, and 6. GluR2/3-immunoreactive cells were distributed mainly in layers 2, 3, 5 and 6 as well as layer 4A in V1, and were mostly pyramidal cells. An antibody against GluR4 stained astrocytes evenly distributed across all layers. Both GluR1- and GluR2/3-immunoreactive cells exhibited a distinct gradient in their regional distributon along the pathway: the number of positive cells in each layer increased from area V1 through areas V2, V4 and TEO to area TE. Particularly, the number of GluR2/3-positive cells in layers II and III increased two-fold at the transition from V1 to V2, so that a sharp boundary was seen at the border between the two areas. Darkly stained GluR2/3-positive cells in V1 formed clusters in layers II and III, which were in register with cytochrome oxidase blobs.
The specificity and diversity of the distribution patterns of AMPA receptors along the pathway may at least paritially contribute to the functional diversity of specific neuronal circuits (e.g., blobs vs interblobs) or different visual areas.(Supported by CREST.)

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