Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates melatonin synthesis from rat pineal gland

Abstract The effect of pituitary adenylate cyclase polypeptide (PACAP) on rat pineal was examined. PACAP stimulated melatonin release from cultured dissociated pinealocytes with a 10 4 higher potency than isoproterenol (EC 50 were 30 pM and 250 nM, respectively). The 10 −9 M PACAP stimulation was not inhibited by 5 × 10 −6 M VIP antagonist whereas that of 10 −9 M VIP was reduced by 54%. Kinetic analysis of melatonin release indicated that PACAP acts postsynaptically via receptor activation.