Sensory neurone-specific receptor-mediated regulation of micturition reflex in urethane-anaesthetized rats

•  To investigate the effect of sensory neurone-specific receptors (SNSRs) activation on the micturition reflex in rats.

•  Continuous cystometrograms (CMGs, 0.04 mL/min) were performed in female Sprague-Dawley rats under urethane anaesthesia. •  After stable micturition cycles were established, a selective rat SNSR1 agonist, bovine adrenal medulla 8-22 (BAM8-22), was administered intravenously (i.v.) or intrathecally (i.t.) in normal rats or rats pretreated with capsaicin 4 days before the experiments. •  Micturition variables were recorded and compared before and after drug administration.

•  Administration (i.v.) of BAM8-22 (3-100 µg/kg) significantly increased intercontraction intervals in a dose-dependent fashion, but did not affect residual urine or baseline pressure at any doses tested. •  Administration (i.t.) of BAM8-22 (0.01-0.3 µg) also increased intercontraction intervals in a dose-dependent fashion, but did not affect residual urine or baseline pressure at any doses tested. •  These inhibitory effects of i.v. (30 µg/kg) or i.t. (0.3 µg) administration of BAM8-22 still occurred after capsaicin pretreatment.

•  These results indicate that in urethane-anaesthetized rats activation of SNSRs can inhibit the micturition reflex via pathways independent of capsaicin-sensitive C-fibres. •  Thus SNSRs could be a potential target for the treatment of bladder dysfunction, e.g. overactive bladder.