Effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on cyclic AMP formation in the duck and goose brain

Two molecular forms of pituitary adenylate cyclase-activating polypeptide ( PACAP), i.e., PACAP(27) and PACAP(38) (0.0001-1 mu M), as well as vasoactiv e intestinal polypeptide (VIP; 0.1-3 mu M), have been studied for their eff ects on cyclic AMP formation in the hypothalamus and cerebral cortex of duc k and goose, All three peptides concentration-dependently stimulated cyclic AMP production in the tested brain regions of 2-3-weeks-old (young) ducks, with VIP showing at least one order of magnitude weaker activity than PACA P. This characteristics suggests the existence in the duck's brain of adeny lyl cyclase-linked PAC(1) receptors. Both forms of PACAP also stimulated th e nucleotide formation in the cerebral cortex and hypothalamus of 5-6-month s-old (adult) ducks or geese grown under natural environment. The peptides- evoked effects in adult and young ducks were comparable, and clearly greate r than those found in adult geese. The present data extend our recent obser vations made on chicks, and suggest PACAP to be a potent stimulator of the cyclic AMP generation in the avian central nervous system.