DIFFERENTIAL-EFFECTS OF CGRP ON ADENYLYL-CYCLASE IN ADULT AND EMBRYONIC RAT-BRAIN

THE presence of functional receptors for calcitonin gene-related pepti de (CGRP) in the brain of adult rats and on nerve cell cultures was in vestigated. Neuronal and glial cultures were obtained from mesencephal ons of embryos at gestational day 16. The response to CGRP was tested by measuring the adenylyl cyclase (AC) activity on isolated membranes. CGRP binding in adult rat brains was ineffective in activating AC,whe reas a dose-dependent stimulation of AC activity was induced by the pe ptide both in neuronal and glial cultures. This effect was more pronou nced in the glial cells where high affinity binding sites for CGRP wer e detected. The presence of functional CGRP receptors in embryonic mes encephalic cells, suggests a role for CGRP in the development of rat m esencephalon.