DISTRIBUTION OF PANCREATIC-POLYPEPTIDE RECEPTORS IN THE RAT-BRAIN

Pancreatic polypeptide (PP) is a regulatory peptide that modulates gas trointestinal function. Previously we demonstrated PP receptors in the brainstem and interpeduncular nucleus, and the PP receptors in the br ainstem appear to modulate gastric motility and pancreatic exocrine se cretion. The purpose of this study is to extend our understanding of t he distribution of PP receptors in the rat brain in order to determine the systems that are potentially modulated by PP. Rat brains were stu died using I-125-PP receptor autoradiography on cryostat sections of t he entire brain cut in three planes (horizontal, sagittal, and coronal ). Brain regions exhibiting PP binding sites were confirmed when ident ified in all three planes of section. Saturable PP binding was identif ied in the hypothalamus (arcuate and paraventricular n), the rostral f orebrain (medial preoptic area, anterior olfactory nucleus, islands of Calleja, the dorsal endopiriform n, piriform cortex, and the bed n of the stria terminalis), medial amygdaloid n; the thalamus (anteromedia l thal. n; reuniens thal. n; and paraventricular thal n), the interped uncular red nucleus, substantia nigra, parabrachial n; locus coeruleus , mesencephalic trigeminal n, dorsal motor n of the vagus, the n solit ary tract, and the area postrema. We conclude that PP receptors are di stributed widely throughout the rat brain. The distribution of many of these PP binding sites corresponds to brain regions regulating digest ion and autonomic function. We speculate, based on the patterns of bin ding in the olfactory and limbic systems, that PP receptors might be i nvolved in positive reinforcement of ingestion behavioral as well as m odulation of gastrointestinal function. (C) 1997 Elsevier Science B.V.