The distribution of bovine pancreatic polypeptide-like immunoreactive neurons in rat brain.

Using the indirect immunofluorescent technique, bovine pancreatic polypeptide (BPP)-like immunoreactive nerve fibers and cell bodies were observed widely distributed in rat brain. A detailed stereotaxic atlas of BPP-immunoreactive neurons was prepared. Large numbers of BPP-containing perikarya were observed in the acute nucleus, with scattered cells in the cerebral cortex, nucleus olfactorius anterior, nucleus tractus diagonalis, olfactory tubercle, nucleus accumbens, neostriatum, nucleus interstitialis stria terminalis, nucleus preopticus medialis, area retrochiasmatica, zona interna of the median eminence, substantia grisea centralis, locus coeruleus, nucleus tractus solitarius, and in the region of the nucleus reticularis lateralis. Large numbers of varicose BPP-like nerve fibers were observed in the following nuclei: accumbens, interstitialis stria terminalis, preopticus medialis, preopticus suprachiasmaticus, suprachiasmaticus, periventricular thalamic and hypothalamic, paraventricularis, dorsomedialis, ventromedialis, arcuatus, parabrachialis dorsalis, tractus solitarius and the substantia gelatinosa trigemini. The present findings suggest that a BPP-like peptide may be involved in significant neuronal circuitry, possibly in a neurotransmitter or neuromodulator role. However, the exact identity of this peptide and its physiological role remain to be determined.