Stimulatory effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on cyclic AMP formation in the hypothalamus and cerebral cortex of four avians and rat.

PACAP38 and PACAP27, tested at 0.0001-1 microM, potently stimulated synthesis of cyclic AMP in the hypothalamus and cerebral cortex of chicks; the effects of vasoactive intestinal polypeptide (VIP) in the two brain regions were much weaker, reaching statistical significance only at 3 microM concentration. This characteristics suggests the existence in the bird's brain of adenylyl cyclase-linked PAC1 receptors. PACAP27 (0.001-1 microM) concentration-dependently stimulated cyclic AMP production in the hypothalamus and cerebral cortex of three other birds: duck, goose and turkey; the effects were, however, somewhat lower than those in chicks, but comparable to those found in rats. These data demonstrate PACAP to be capable of potently stimulating cyclic AMP generating system in the avian central nervous system.