THE EFFECT OF PITUITARY ADENYLATE-CYCLASE ACTIVATING PEPTIDE (PACAP) ON THE NOCICEPTIVE FORMALIN TEST

Recent studies have suggested that pituitary adenylate cyclase activat ing peptide (PACAP) may be involved in nociceptive transmission. The p resent study examined the effect of low-dose PACAP-27 on nociceptive b ehavior using the formalin test. PACAP-27 was administered intrathecal ly. Twenty minutes later, formalin (50 mu l, 5%) was injected subcutan eously into the dorsal surface of the right hind paw. Intrathecal PACA P-27 at 0.6 pmol suppressed the second phase response to formalin, whi le 5 pmol depressed both phases. PACAP-27 at 5 pmol did not impair mot or function. Hence, the data suggest that the effect of PACAP-27 on fo rmalin-induced pain-related behavior is specific, The findings may lea d to a better understanding of the role of PACAP in nociceptive transm ission.