COMPARATIVE DISTRIBUTION OF RECEPTORS FOR AMYLIN AND THE RELATED PEPTIDES CALCITONIN-GENE-RELATED PEPTIDE AND CALCITONIN IN RAT AND MONKEY BRAIN

The distribution of amylin receptors (I-125-labelled rat amylin) in br ains of rat and monkey were mapped and compared with the distribution of receptors for calcitonin (CT) (I-125-labelled salmon CT) and calcit onin gene related peptide (CGRP) (rat, I-125-labelled rat CGRP alpha; monkey, I-125-labelled human CGRP alpha). In rat, amylin receptors wer e discretely distributed with the highest receptor densities found in mid-caudal accumbens nucleus, parts of the bed nucleus of the stria te rminalis, amygdala, and hypothalamus. Moderate to high densities of bi nding also occurred in the area postrema, subfornical organ, vascular organ of the lamina terminalis, locus ceruleus, dorsal raphe, and caud al solitary tract nucleus. In monkey, the distribution of amylin bindi ng sites was similar, although the highest densities of receptors were in the hypothalamus, with relatively fewer sites present in the accum bens nucleus. In rat, the distribution of amylin receptors formed a su bset of the receptor distributions for I-125-labelled salmon CT and I- 125-labelled rat CGRP alpha. In contrast, in monkey, although the amyl in receptors again formed a subset of the binding sites identified wit h I-125-labelled salmon CT, there was very little overlap with the pat tern of CGRP receptor distribution. This suggests that the specificity profile of amylin receptors in primates differs from that of amylin r eceptors in the rat, with CGRP alpha having relatively lower affinity for the primate amylin receptors.