COLOCALIZATION OF CALBINDIN D-28K, CALRETININ, AND GABA IMMUNOREACTIVITIES IN NEURONS OF THE HUMAN TEMPORAL CORTEX

The calcium-binding proteins calbindin D-28k (CalB) and calretinin (Ca lR) have been shown to be useful markers of neuronal subpopulations lo cated mainly in layers II-III of the neocortex of a variety of species , including human. Double labeling immunocytochemical studies of GIB, CalR, and GA8A in experimental animals have shown that CalB and CalR a re present in separate subpopulations of neurons. However, there are n o studies of colocalization of these calcium-binding proteins and GABA in the human neocortex. The principal goal of the present work was to investigate the degree of colocalization of these substances in layer s II-III of the human temporal neocortex, using a postembedding immuno cytochemical method. The patterns of staining for CalB, Cain, and GABA in the human cortex were similar to those found in monkey neocortex. However, the degree of colocalization for certain combinations was dif ferent from that reported in the monkey and other experimental animals . A relatively large proportion of CalB- and CalR-immunoreactive cells (approximately 71% and 74%, respectively) were found to be immunoreac tive for GABA, However, the degree of colocalization of CalB with CalR was low (between 4% and 6%). Thus, our quantitative and qualitative d ata suggest that these calcium-binding proteins are present in similar cortical circuits in all primates, but that in the human neocortex, t here might be additional GABAergic and perhaps also non-GABAergic inte rneurons with unique chemical characteristics. (C) 1996 Wiley-Liss, In c.