Effect of Centrally Administered Cannabinoids on Bladder Function

Abstract

Recent studies demonstrated a dose-dependent relationship between bladder function and peripheral administration of cannabinoids (CAN) on cat bladder. Low doses of cannabinoids increase bladder detrusor muscle activity, while high doses decrease detrusor activity. The increase is manifested as an increase in frequency of spontaneous bladder contractions, and the decrease as a greater micturition volume threshold (MVT) and time to onset of contractions. Decreased activity is manifested as a decrease in frequency of contractions, and an increase in MVT and time to onset of contractions. Studies have shown that the periaqueductal gray area (PAG), contains endogenous CAN receptors, which should respond to CAN administration. This study assessed the effects of CP 55,940 (CP) microinjected into the PMC on bladder function comparing them to those seen following peripherally administered CP. Also, the CAN receptor antagonist AM 251 was used to confirm that the effects of CP on bladder function were mediated by CB1 receptors. After the urinary bladder was instrumented, a guide cannula was placed into an area directly above the PMC. CP was administered centrally into the PMC or peripherally via the lumbar colonic artery. Data from these studies indicate that centrally administered CP produces dose dependent effects on the time to onset and frequency of spontaneous contractions, and micturition volume threshold similar to the effects produced by peripherally administered CP.