The Journal of urology
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The Journal of urology · Oct 1993
Intraurethral capsaicin produces reflex activation of the striated urethral sphincter in urethane-anesthetized male rats.
The effect of intraurethral application of capsaicin on the urethral motility of urethane anesthetized rats has been investigated. The urinary bladder and the urethra were surgically disconnected, and both organs were cannulated to record variations in intraluminal pressure (cystourethrogram). Urinary bladder reflex contractions in response to intravesical infusion of saline were paralleled by activation of the external striated urethral sphincter, resulting in intraluminal pressure high frequency oscillations (IPHFO) which were recorded at the urethral level. ⋯ Electrical field stimulation (EFS, 0.1 Hz, 30 microseconds, 20 to 30 v) of the rat isolated external urethral sphincter (EUS), elicited d-tubocurarine and tetrodotoxin-sensitive twitch contractions, the amplitude of which was unaffected by capsaicin (1 microM.). Altogether these results suggest a physiological interaction between capsaicin-sensitive primary afferents innervating the urethra and the somatic efferent innervation to the urethral rabdosphincter. Present findings suggest the existence of a chemonociceptive urethro-urethral neural loop which, via pudendal nerves, leads to a supraspinally-mediated activation of the external urethral sphincter.