title: Effects of menthol on circular smooth muscle of human colon: analysis of the mechanism of action.
abstract: Menthol is the major constituent of peppermint oil, an herbal preparation commonly used to treat nausea, spasms during colonoscopy and irritable bowel disease. The mechanism responsible for its spasmolytic action remains unclear. The aims of this study were to investigate the effects induced by menthol on the human distal colon mechanical activity in vitro and to analyze the mechanism of action. The spontaneous or evoked-contractions of the circular smooth muscle were recorded using vertical organ bath. Menthol (0.1 mM-30 mM) reduced, in a concentration-dependent manner, the amplitude of the spontaneous contractions without affecting the frequency and the resting basal tone. The inhibitory effect was not affected by 5-benzyloxytryptamine (1 μM), a transient receptor potential-melastatin8 channel antagonist, or tetrodotoxin (1 μM), a neural blocker, or 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (10 µM), inhibitor of nitric oxide (NO)-sensitive soluble guanylyl cyclase, or tetraethylammonium (10 mM), a blocker of potassium (K+)-channels. On the contrary, nifedipine (3 nM), a voltage-activated L-type Ca2+ channel blocker, significantly reduced the inhibitory menthol actions. Menthol also reduced in a concentration-dependent manner the contractile responses caused by exogenous application of Ca2+ (75-375 μM) in a Ca2+-free solution, or induced by potassium chloride (KCl; 40 mM). Moreover menthol (1-3 mM) strongly reduced the electrical field stimulation (EFS)-evoked atropine-sensitive contractions and the carbachol-contractile responses. The present results suggest that menthol induces spasmolytic effects in human colon circular muscle inhibiting directly the gastrointestinal smooth muscle contractility, through the block of Ca2+ influx through sarcolemma L-type Ca2+ channels.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy. Electronic address: antonella.amato@unipa.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Amato
authors.affiliation: Mediterranean Institute For Transplantation and Advanced Specialized Therapies (ISMETT), Palermo, Italy.
authors.forename: Rosa
authors.initials: R
authors.lastname: Liotta
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Mulè
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002217:Carbachol; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008610:Menthol / Q000494:pharmacology*; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D010276:Parasympatholytics / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D010276:Parasympatholytics; D008610:Menthol; D002217:Carbachol; D009543:Nifedipine
keywords: Calcium channels; Human colon; Menthol; Motility; TRPM8