Cholecystokinin and bradykinin: putative peptide neurotransmitters

Abstract

Cholecystokinin (CCK) and bradykinin are two peptides which have joined the rapidly expanding group of putative peptide neurotransmitters. CCK, originally identified as an intestinal hormone, is found in mammalian brain in high concentrations. Immunofluorescence staining of rat brain shows an extensive distribution of CCK-8-like immunoreactivity. Particularly dense collections of positively stained cell bodies occur in dorsal and perirhinal cortices, hippocampus, hypothalamus and periaqueductal grey. One can speculate that CCK’s role in feeding is mediated by the neuronal systems in the hypothalamus. Bradykinin is a nonapeptide first found in mammalian blood and subsequently shown to be involved in inflammation and pain generation. Bradykinin-like immunoreactivity in rat brain was found in neuronal cell bodies only in the hypothalamus or closely adjacent regions. Positively stained fibres in the lateral septal area may mediate the hypertensive response elicited by the intracerebroventricular administration of bradykinin. Similarly, fibres in the periaqueductal grey may mediate the analgesic effect of centrally administered bradykinin.