Activation of the rostral pontine reticular formation increases the spinal glycine level and inhibits bladder contraction in rats

Purpose: We examined the mechanism involved in the inhibition of bladder activity in rats by stimulating the rostral pontine reticular formation (RPRF) using carbachol, flavoxate and propiverine, and by analysis of amino acid levels in the lumbosacral cord. Materials and Methods: A total of 82 female rats were anesthetized with urethane. Under isovolumetric conditions physiological saline, carbachol, flavoxate or propiverine was injected into the RPRF or intravenously. Changes in bladder activity and amino acid levels in the lumbosacral cord were examined. Results: Injection of carbachol or flavoxate (0.3 mu M each) into the RPRF abolished bladder contraction but there was no change after injection of physiological saline or propiverine. Intravenous injection of flavoxate or propiverine (0.1 to 10 mg/kg each) inhibited bladder contraction. Amino acid analysis revealed that injection of carbachol into the RPRF increased glutamate and glycine levels in the lumbosacral cord, while injection of flavoxate into the RPRF or intravenously caused an increase in glycine the lumbosacral cord. Injection of propiverine into the RPRF or intravenously did not influence lumbosacral cord amino acid levels. Conclusions: These results suggest that the RPRF has an important role in the inhibition of bladder contraction and carbachol or flavoxate can activate descending RPRF neurons and inhibit bladder contraction via spinal glycinergic neurons.