PACAP (6-38), human, ovine, rat

PACAP (6-38) is a potent antagonist of PACAP 38. PACAP (6-38) is much more potent and selective than PACAP (6-27) in the inhibition of PACAP-27-stimulated pituitary adenylate cyclase. Ki values for the inhibition of the enzyme were 7nM and 150 nM, respectively. PACAP (6-38) caused a small but significant (approximately 20%) inhibition of the NANC relaxation due to electrical field stimulation (1 Hz or 10 Hz for 20 s). At these frequencies PACAP (6-38) caused no inhibition of the NANC relaxation in the presence of the P2 purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid (or PPADS) plus the NO-synthase blocker NG-nitro-L-arginine; in preparations pretreated with L-NOARG alone, PACAP (6-38) retained its inhibitory effect.