Stimulation of skin menthol receptors stimulates detrusor activity in conscious rats.

Aims: The Transient Receptor Potential Melastatin (TRPM)8 channel, activated by menthol and cool temperatures, has been proposed to be a cool receptor involved in mediation of the bladder response in the diagnostic ice water test. We examined the expression of TRPM8 in the rat skin and investigated if stimulation of skin menthol receptors by menthol can induce detrusor activity in conscious rats.

Methods: Immunofluorescence staining for TRPM8 was performed in samples of the skin from the leg and back of the rats. Continuous cystometry was performed in conscious animals. Voiding interval (VI), micturition volume (MV), and bladder capacity (BC) were evaluated before and after spraying menthol solution to the skin of the leg and back of the rats.

Results: Immunohistochemical analysis revealed that TRPM8 was expressed in the investigated tissues. The expression of TRPM8-positive receptors was not significantly different between the leg and back skin. Saline caused no significant change in cystometric parameters. After spraying menthol solution (50% and 99% to the skin of the leg, and 99% to the back skin), VI, MV, and BC decreased significantly.

Conclusions: TRPM8 is expressed in rat skin. Spraying menthol solution onto the skin-induced detrusor activity, an effect we suggest is mediated by stimulation of TRPM8 receptors.