Morphine and the centrally-mediated inhibition of urinary bladder motility in the rat

Systemic administration of morphine consistently inhibited spontaneous urinary bladder contractions in the ketamine-anesthetized rat. In addition, i.c.v. morphine and levorphanol but not dextrophan inhibited bladder function by a naloxone-sensitive mechanism. Naloxone alone increased the frequency of bladder contractions and intravesicular pressure. Systemic loperamide did not affect bladder function while N,N- diallylnormorphinium only reversed bladder inhibition by morphine when administered i.c.v. These observations suggest that morphine inhibits bladder activity by a central mechanism and that endogenous opioids are involved in the central control of bladder function.