Sex difference in urethral response to electrical stimulation of efferent nerves in the pudendal sensory branch of rats

Background: We reported sex difference in the urethral pressure (UP) response to electrical stimulation (ES) of the hypogastric nerve in rats. The purpose of the present study was to report on sex difference in the UP response to ES of the pudendal nerves (PN) in rats before and after injection of d-tubocurarine (d-tc). Methods: Wistar rats were anesthetized with urethane and α-chloralose. The L6-S1 trunk was exposed on the left side and resected. After resection of the motor branch of the PN the peripheral end of the L6-S1 trunk was stimulated. Fluid was infused into the urethra through a catheter inserted into the bladder neck at a constant rate (0.5 mL/10 min) and the infusion resistance was measured as the UP. When d-tc was injected, the rats were ventilated with an artificial respirator. Results: Though ES of the L6-S1 trunk caused fibrillation of the muscles near the tail and steep reduction of the UP, it caused elevation and reduction of UP in male and female rats, respectively, after intravenous injection of d-tc (0.3 mg/kg). ES of the sensory branch of the PN caused the elevation in male rats and reduction of the UP without injection of d-tc, and prazosin inhibited the UP elevation but the reduction was not inhibited by Nω-nitro-L-arginine methyl ester. Conclusion: In the sensory branch of the PN, the nerves innervating the smooth muscles in the urethral sphincter were contained. In male rats norepinephrine mediates the UP elevation, but the neurotransmitter that mediates the UP reduction in female rats is not known.