title: Inhibitory effects of magnolol on distal colon of guinea pig in vitro.
abstract: The influence of plant product magnolol (0-100 microM) on the contractile activity of isolated colonic muscle strips in guinea pig and related mechanism were investigated. Magnolol did not affect the base tone of colon muscle strips, but it dose-dependently inhibited 40 mM KCl-, 1 microM carbachol (CCh)- and 10 microM serotonin (5-HT)-induced contractions at concentrations higher than 10 microM. And also, magnolol inhibited the 5-HT- or CCh-induced muscle contraction in calcium-free buffer. Furthermore, magnolol inhibited the KCl-induced contraction under the condition of procaine. In addition, inhibition rate of nifedipine plus magnolol on muscle strips was lower than that of nifedipine alone. Moreover, magnolol dose-dependently decreased the velocity of pellet propulsion in the concentration range of 0.1-10 microM, and totally inhibited pellet propulsion at the concentration higher than 30 microM. Thus, it can be concluded that magnolol may 1) block receptor-operated cation channels and the voltage dependent Ca2+ channel, and 2) inhibit calcium release from the sarcolemmal membrane (SR) through blocking InsP3-sensitive and ryanodine-sensitive pathways. This explains, at least partially, that Cortex magnoliae officinalis exerts therapeutic effects on gastrointestinal disease through relaxation of GI tract smooth muscles.
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR. bzxiang@hkbu.edu.hk
authors.forename: Zhao Xiang
authors.initials: ZX
authors.lastname: Bian
authors.forename: Gen Shui
authors.initials: GS
authors.lastname: Zhang
authors.forename: Ka Leung
authors.initials: KL
authors.lastname: Wong
authors.forename: Xu Guang
authors.initials: XG
authors.lastname: Hu
authors.forename: Liang
authors.initials: L
authors.lastname: Liu
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Yang
authors.forename: Min
authors.initials: M
authors.lastname: Li
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D003106:Colon / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005765:Gastrointestinal Agents / Q000494:pharmacology*; D005772:Gastrointestinal Transit / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D017705:Lignans / Q000494:pharmacology*; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D001713:Biphenyl Compounds; D002121:Calcium Channel Blockers; D005765:Gastrointestinal Agents; D017705:Lignans; D018721:Muscarinic Agonists; C005498:magnolol; D012701:Serotonin; D011343:Procaine; D011189:Potassium Chloride; D002217:Carbachol; D009543:Nifedipine