Brain cannabinoid CB₁ receptors suppress centrally administered bombesin-induced facilitation of the rat micturition

Abstract

To clarify roles of brain cannabinoid CB 1 receptors in regulation of the micturition, we examined the effects of intracerebroventricularly (icv) administered rimonabant (Rimo, a CB 1 antagonist) and JZL195 (JZL, an inhibitor of enzymes related to degradation of endogenous CB receptor ligands) on icv administered bombesin (BB, a stressrelated neuropeptide)-induced facilitation of the micturition in urethane-anesthetized (0.8 g/kg, ip) male Wistar rats. A catheter was inserted into the bladder to perform cystometry. Three hours after the surgery, JZL (10 or 30 nmol/rat) or Rimo (100 or 300 nmol/rat) was icv administered 30 min before BB administration (0.01 or 0.03 nmol/rat, icv). BB (0.03 nmol) shortened the intercontraction interval (ICI), an indicator of micturition frequency, while JZL significantly suppressed the BB-induced response. BB at a lower dose (0.01 nmol) showed no significant effect on ICI, while the BB significantly shortened ICI after pretreatment with Rimo. In addition, JZL-induced suppression of the BB (0.03 nmol)-induced response was abolished in the presence of Rimo. These results indicate that brain CB 1 receptors suppress the centrally administered BB-induced facilitation of the rat micturition.