title: TRPM8 agonists modulate contraction of the pig urinary bladder.
abstract: The transient receptor potential melastin-8 (TRPM8) channel is activated by the "cooling" compounds menthol and icilin. Pathophysiologically, it is implicated in the overactive bladder and bladder cooling reflex, but the activity of TRPM8 in normal bladder physiology is poorly understood. We investigated the distribution of TRPM8 channels and the effect of TRPM8 agonists on the contractile function of pig bladder (n = 35) strips and whole bladders. The distribution of TRPM8 was examined by immunohistochemistry. The effect of vesical or intravascular menthol (0.1-0.3 mmol/L) or icilin (50 μmol/L) on carbachol-induced isolated whole bladder contractions was monitored by recording vesical pressure. Strips of denuded detrusor or mucosa were mounted in organ baths to study the effect of TRPM8 agonists on the contractile responses to 10 μmol/L carbachol. TRPM8-like immunoreactivity was detected on pig urothelium. Intravascular menthol (0.3 mmol/L) and icilin (50 μmol/L) significantly decreased the magnitude of carbachol-induced whole bladder contraction, whereas vesical administration significantly increased the response. In detrusor and mucosal strips, both menthol (0.3 mmol/L) and icilin (50 μmol/L) inhibited carbachol-induced contractions. We conclude that the TRPM8 channel is expressed on the urothelium of pig bladder. In the whole organ, exposure of the urothelium to menthol or icilin increases the contractile response to carbachol. Where detrusor muscle is exposed directly to these compounds, the contractile response to carbachol is reduced.
authors.affiliation: University of the West of England, Department of Applied Sciences, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK. bahareh.vahabi@uwe.ac.uk
authors.forename: Bahareh
authors.initials: B
authors.lastname: Vahabi
authors.forename: Brian A
authors.initials: BA
authors.lastname: Parsons
authors.forename: Olena
authors.initials: O
authors.lastname: Doran
authors.forename: Anthony
authors.initials: A
authors.lastname: Rhodes
authors.forename: Sarah
authors.initials: S
authors.lastname: Dean
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Drake
mesh_terms: D000818:Animals; D005260:Female; D008610:Menthol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D011744:Pyrimidinones / Q000494:pharmacology; D013552:Swine; D050053:TRPM Cation Channels / Q000819:agonists* / Q000378:metabolism; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism; D019459:Urothelium / Q000187:drug effects* / Q000378:metabolism
chemical_list: D011744:Pyrimidinones; D050053:TRPM Cation Channels; D008610:Menthol; C490483:icilin