title: Terpinen-4-ol: mechanisms of relaxation on rabbit duodenum.
abstract: The effect of terpinen-4-ol was studied on rabbit duodenum in-vitro. Terpinen-4-ol induced relaxation of the basal tonus (IC50 170.2 (95% confidence interval, 175-204) microM) with a maximal relaxant response of 180.4+/-3.9% (n=6) of the contraction induced by 60 mM [K(+)]. The maximal relaxation induced in control conditions was not affected (P>0.05) by pretreatment of the tissues with phentolamine (50 microM) or propranolol (10 microM), N(G) nitro-L-arginine methyl ester (L-NAME; 1 mM), 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 100 microM), hexamethonium (1 mM), tetrodotoxin (1 microM), the mixture charybdotoxin-apamin (1 microM), glibenclamide (10 microM), 4-aminopyridine (10 microM) or tetraethyl-ammonium (100 microM). In addition, terpinen-4-ol completely relaxed tissues precontracted with 60 mM [K(+)] solutions (IC50 325.9 (245.1-433.1) microM) and also blocked (IC50 154.7 (117.7-191.7) microM) the phasic component of this contraction. At a concentration of 195 and 650 muM it reduced by 41.3+/-3.4% and 75.4+/-3.1%, respectively the maximal contractile response to Ca(2+) in depolarized duodenum. Terpinen-4-ol completely blocked the component of carbachol-induced contraction, which was resistant to nifedipine (100 microM) pretreatment or to a Ca(2+)-free solution. These data show that terpinen-4-ol relaxes intestinal smooth muscle and suggest that this effect is myogenic in nature and depends on calcium antagonism.
authors.affiliation: Superior Institute of Biomedical Sciences, State University of Ceara, Av. Paranjana 1700, Campus do Itaperi, CEP 60740-000, Fortaleza-CE, Brazil.
authors.forename: Nilberto R F
authors.initials: NR
authors.lastname: Nascimento
authors.forename: José H
authors.initials: JH
authors.lastname: Leal-Cardoso
authors.forename: Lucília M A
authors.initials: LM
authors.lastname: Lessa
authors.forename: Jarbas S
authors.initials: JS
authors.lastname: Roriz-Filho
authors.forename: Karina M A
authors.initials: KM
authors.lastname: Cunha
authors.forename: Manassés C
authors.initials: MC
authors.lastname: Fonteles
mesh_terms: D000818:Animals; D004386:Duodenum / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D010276:Parasympatholytics / Q000494:pharmacology*; D011817:Rabbits; D013729:Terpenes / Q000494:pharmacology*
chemical_list: D010276:Parasympatholytics; D013729:Terpenes; C034019:terpinenol-4