Influence of glutamatergic projections to the rostral pontine reticular formation on micturition in rats

AimsWe examined the effect of injecting glutamate or a glutamate receptor antagonist into the rostral pontine reticular formation (RPRF) on the micturition reflex in anesthetized rats and conscious rats.Main methodForty-eight female rats were divided into an isovolumetric cystometry group and a continuous cystometry group. Under urethane anesthesia or while conscious, physiological saline, glutamate, or MK-801 (a glutamate receptor antagonist) was injected into the RPRF, and then the changes of bladder activity were examined.Key findingsThere was no significant change of bladder activity after injection of physiological saline. In anesthetized rats, the injection of either glutamate or MK-801 into the RPRF transiently inhibited bladder contractions. There was a complete recovery of bladder activity 10–20 min after glutamate or MK-801 injection and there were no significant changes of cystometry parameters after the recovery of bladder contractions. In conscious rats, injection of glutamate into the RPRF prolonged the interval between bladder contractions and decreased the baseline bladder pressure. On the other hand, injection of MK-801 into the RPRF caused numerous small bladder contractions, some of which were accompanied by a leakage of a small amount of fluid from around the urethral catheter.SignificanceRPRF neurons receive glutamatergic projections, possibly from the forebrain, and the RPRF inhibits the micturition reflex pathway. RPRF neurons are also regulated by inhibitory interneurons, which receive glutamatergic projections as well. Therefore, the RPRF plays an important role in the regulation of urine storage.