CALRETININ-IMMUNOREACTIVE CELLS AND FIBERS IN THE HUMAN AMYGDALOID COMPLEX

Calretinin is a calcium-binding protein that colocalizes with GABA in the cerebral cortex and hippocampus of the rat and the monkey. In the present study, we investigated the distribution of calretinin-immunore active cells and fibers in the human amygdaloid complex. A conspicuous feature was the high density of calretinin neurons in the human amygd ala. The highest densities of the calretinin-immunoreactive neurons we re observed in the anterior cortical nucleus, accessory basal nucleus, amygdalohippocampal area, and in the nucleus of the lateral olfactory tract. The paralaminar nucleus, central nucleus, medial nucleus, and the periamygdaloid cortex contained the lowest densities of calretinin neurons. In most of the amygdaloid areas, the calretinin cells had th e appearance of aspiny or sparsely spiny local circuit neurons. Howeve r, in the amygdalohippocampal area, we found also densely spined dendr ites. The cortical areas and the central nucleus were characterized by intense neuropil labeling, while the deep nuclei contained a high den sity of calretinin-immunoreactive fibers and terminals. Calretinin imm unoreactivity was also found in the intra-amygdaloid fiber bundles, st ria terminalis, and in the ventral amygdalofugal pathway. This suggest s that in addition to the local circuit neurons, calretinin immunoreac tivity is also located in neurons that connect the amygdaloid complex with the other brain areas. The distribution and morphological charact eristics of calretinin-immunoreactive neurons differed from those of a nother calcium-binding protein, parvalbumin, in the human amygdala (So rvari et al. [1995] J. Comp. Neurol. 360:185-212). This suggests that these two calcium-binding proteins are located in different population s of neurons. (C) 1996 Wiley-Liss, Inc.