Stimulation of skin menthol receptors stimulates detrusor activity in conscious rats.
OBJECTIVE
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.
Chen
Zhong
Z
Department of Urology, Shinshu University School of Medicine, Matsumoto, Japan. chenzhongchina@hotmail.com
Ishizuka
Osamu
O
Imamura
Tetsuya
T
Aizawa
Naoki
N
Kurizaki
Yoshiki
Y
Igawa
Yasuhiko
Y
Nishizawa
Osamu
O
Andersson
Karl-Erik
KE
D000287:Administration, Topical; D000818:Animals; D003243:Consciousness; D005260:Female; D008610:Menthol / Q000008:administration & dosage; D009130:Muscle, Smooth / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000378:metabolism*; D050053:TRPM Cation Channels / Q000096:biosynthesis* / Q000502:physiology; D001743:Urinary Bladder / Q000502:physiology*
D050053:TRPM Cation Channels; C498947:Trpm8 protein, rat; D008610:Menthol