Cellular distribution of the splice variants of the receptor for pituitaryadenylate cyclase-activating polypeptide (PAC(1)-R) in the rat brain by insitu RT-PCR

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide and its specific receptor (the PAC(1) receptor) is widely dis tributed in the rat brain. It has been reported that alternative splicing o f the region encoding the third intracellular loop of the PAC(1) receptor g enerates six isoforms which are differentially coupled to signal transducti on pathways, but the precise distribution and localization of these splice isoforms in the brain remain to be determined. Using the initial specific p rimer pairs which correspond to the 'hip' or 'hop' types of receptors for t he solution-phase reverse transcription-polymerase chain reaction (RT-PCR), we demonstrated that the major splice variants of the PAC(1) receptor in v arious regions of the rat brain are the short splice isoform 'PAC(1)-R-s' w hich does not contain either the 'hip' or 'hop' cassette and the another sp lice isoform, 'PAC(1)-R-hop', which contains the 'hop' cassette. With an in novative molecular histochemical technique, in situ RT-PCR, we determined t hat these two splice isoforms are both intensely expressed in the mitral te lls of the olfactory bulb, the Purkinje cells of the cerebellum, the pyrami dal cells of the hippocampus and neocortex, and many neurons in the nuclei of hypothalamus and thalamus as well as other regions. The initial mapping of the cell type-specific expression of these two splice variants of the PA C(1) receptor provides the basis for a better understanding of the function al significance of the PAC(1)-R and its ligand PACAP in various brain regio ns. (C) 2000 Published by Elsevier Science B.V. All rights reserved.