Effect of menthol on the bladder cooling reflex in the cat

The effect of menthol on the urinary bladder cooling reflex was studied in alpha-chloralose-anaesthetized cats. The cooling reflex was elicited by bladder or urethral instillations of cold saline and monitored by multiunit recordings from efferent and afferent pelvic nerve filaments. The bladder cooling reflex was greatly exaggerated by intraluminal exposure of the bladder or the urethra to a 0.6 mM solution of menthol. The effect occurred without a sensitizing effect on bladder mechanoreceptors. It could be described as a shift of the temperature-response curve for the cooling reflex towards higher temperatures. This change resembles the effect of menthol on cutaneous cold receptors. It is proposed that the bladder cooling reflex originates from cold receptors in the bladder and urethral walls.