Immunohistochemical distribution of neuropeptides in the amygdaloid complex of the cat. A comparative study in mammals

The distribution of several neuropeptides in the amygdaloid complex of the cat is described. Five of the neuropeptides studied (luteinizing hormone-releasing hormone, β-endorphin, dynorphin A (1-17), γ-melanocyte-stimulating hormone or galanin) did not show immunoreactive profiles, whereas neuropeptide Y and somatostatin displayed the widest distribution throughout the amygdaloid nuclei. The medial amygdala (medial nucleus, medial division of the central nucleus) contained the highest number of the n e u ropeptides studied, whereas the lateral nucleus displayed the lowest amount of immunoreactive profiles. In addition, the morphological data suggest the possible co-existence of several neuropeptides in the same fibers and/or cell bodies, and a comparison with previous studies on the projections of the amygdaloid nuclei in the cat allows us to speculate about the possible peptidergic content of these pathways. The distribution of the neuropeptides studied in the cat is compared with the location of the same peptides in the amygdaloid complex of other mammalian species. Finally, the possible physiological functions of the neuropeptides, as well as aspects of future research into the morphology of neuropeptides in the cat amygdala are discussed.