Pituitary adenylate cyclase activating polypepetide is expressed by developing rat Purkinje cells and decreases the number of cerebellar gamma-amino butyric acid positive neurons in culture

The neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) is expressed in various parts of the developing and adult rat brain, inclu ding the cerebellum, In situ hybridization was employed to localize the pre cise site of mRNA expression for PACAP and PACAP receptor I (PRI). During p renatal cerebellar development, PACAP mRNA was present in developing Purkin je cells and some deep cerebellar nuclei, whilst PRI mRNA was expressed by adjacent cells in the Purkinje cell layer (PCL). There was a shift in PRI m RNA expression to the external germinal cell layer around birth. PACAP decr eased the number of neurons positive for the inhibitory neurotransmitter ga mma-amino butyric acid (GABA) in cultures from embryonic cerebellum, but di d not affect overall cell survival. In conclusion, our results show the pat tern of PACAP mftNA expression in embryonic cerebellum and suggest a physio logical role for PACAP on GABAergic cerebellar neurons. (C) 1999 Elsevier S cience Ireland Ltd. All rights reserved.