Excitatory amino acid, GABA(A), and GABA(B) binding sites in human striate cortex

Receptor autoradiography was used to study the laminar distribution of excitatory amino acid, GABA(A), and GABA(B) binding sites in human striate cortex. Binding sites for all these receptor subtypes were found within striate cortex, but there were marked differences in the laminar distribution of binding sites. NMDA binding sites were most dense in layers 1-4C, with highest density in layer 4C and lower levels in layers 5 and 6. Among non-NMDA binding sites, alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid binding sites had highest levels in layers 1-3, intermediate levels in layers 5 and 6, and lowest levels in layers 4B and 4C. Kainate and metabotropic binding sites were more uniformly distributed across cortical laminae, with a trend toward highest kainate binding in layers 5 and 6. GABA(A)/benzodiazepine binding sites had highest levels in layers 2, 3, and 4C, with intermediate levels in 4B and lowest levels in layers 1, 5, and 6. GABA(B) binding sites were uniformly distributed across laminae. There was no evidence of a "columnar" or "blob" pattern of any binding site within any of the laminae. With the exception of kainate, metabotropic excitatory amino acid, and GABA(B) binding sites, the laminar distribution of binding sites within striate cortex was different than that seen in adjacent visual cortex.