FACILITATORY EFFECT OF PITUITARY ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE ON MICTURITION IN NORMAL, CONSCIOUS RATS

In unanaesthetized, normal rats, continuous cystometry revealed that pituitary adenylate cyclase activating peptide (PACAP-27), administered intrathecally or intra-arterially near the bladder, stimulated micturition. The localization of PACAP-27 in the rat lower urinary tract was studied by immunohistochemistry, and the direct effects on the smooth muscles of the rat detrusor and urethra were investigated in vitro. In the intact rat, 1.0 nmol of PACAP-27 administered intrathecally as well as intra-arterially close to the bladder, but not intravenously, increased micturition pressure, decreased micturition volume and bladder capacity, and facilitated spontaneous bladder contractions. PACAP-27 immunoreactive structures were extremely scarce in the lower urinary tract, and the peptide had negligible effects on isolated detrusor muscle contracted by carbachol or stimulated electrically, or on urethral preparations contracted by noradrenaline. These results suggest that PACAP-27 has facilitatory actions on micturition both at the spinal cord and peripheral ganglionic levels.