title: Inhibitory effect of mitragynine, an analgesic alkaloid from Thai herbal medicine, on neurogenic contraction of the vas deferens.
abstract: The effect of an indole-alkaloid mitragynine isolated from the Thai medicinal herb kratom (Mitragyna speciosa) on neurogenic contraction of smooth muscle was studied in guinea-pig vas deferens. Mitragynine inhibited the contraction of the vas deferens produced by electrical transmural stimulation. On the other hand, mitragynine failed to affect the responses to norepinephrine and ATP. Mitragynine did not reduce KCl-induced contraction in the presence of tetrodotoxin, prazosin and alpha,beta-methylene ATP. Mitragynine inhibited nicotine- or tyramine-induced contraction. By using the patch-clamp technique, mitragynine was found to block T- and L-type Ca2+ channel currents in N1E-115 neuroblastoma cells. In the Ca2+ measurement by a fluorescent dye method, mitragynine reduced KCl-induced Ca2+ influx in neuroblastoma cells. The present results suggest that mitragynine inhibits the vas deferens contraction elicited by nerve stimulation, probably through its blockade of neuronal Ca2+ channels.
authors.affiliation: Department of Pharmacology, Faculty of Pharmaceutical Sciences, Josai International University, 1 Gumyo, Togane, Chiba 283-8555, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Leonardo T
authors.initials: LT
authors.lastname: Yamamoto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Watanabe
authors.forename: Shingo
authors.initials: S
authors.lastname: Yano
authors.forename: Jie
authors.initials: J
authors.lastname: Shan
authors.forename: Peter K T
authors.initials: PK
authors.lastname: Pang
authors.forename: Dhavadee
authors.initials: D
authors.lastname: Ponglux
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Takayama
authors.forename: Syunji
authors.initials: S
authors.lastname: Horie
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D018663:Adrenergic Agents / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009447:Neuroblastoma / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D028321:Plant Preparations; D011189:Potassium Chloride / Q000494:pharmacology; D046948:Secologanin Tryptamine Alkaloids / Q000494:pharmacology*; D013785:Thailand; D014439:Tyramine / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects* / Q000294:innervation*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D018663:Adrenergic Agents; D000700:Analgesics; D015220:Calcium Channels; D018722:Nicotinic Agonists; D028321:Plant Preparations; D046948:Secologanin Tryptamine Alkaloids; D014662:Vasoconstrictor Agents; D011189:Potassium Chloride; D009538:Nicotine; D000255:Adenosine Triphosphate; C001801:mitragynine; D002118:Calcium; D009638:Norepinephrine; D014439:Tyramine