The effect of pelvic nerve stimulation and some drugs on the urethra and bladder of the dog.

Pelvic nerve stimulation caused an increase in pressure in both the urethra and bladder of anaesthetised dogs. The increases were only partially blocked by intravenous injection of atropine and were not significantly reduced by phentolamine, propranolol or methysergide. Quinidine produced some reduction in the bladder but not the urethral response. Hexamethonium reduced but did not abolish the responses to pelvic nerve stimulation. Close arterial injection of acetylcholine and 5-hydroxytryptamine increased the bladder and urethral pressures; noradrenaline produced a biphasic increase in urethral pressure but had no effect on the bladder; ATP increased bladder pressure but the response of the urethra was variable. The results indicate that some fibres in the pelvic nerve to the urethra as well as to the bladder are atropine resistant and suggest that transmission does not involve 5-hydroxytryptamine or noradrenaline and probably not ATP. The significance for treatment of detrusor dysfunction is discussed.