title: Relaxant effect induced by wogonin from Scutellaria baicalensis on rat isolated uterine smooth muscle.
abstract: BACKGROUND
  Wogonin is a flavone derivative isolated from Scutellaria baicalensis Georgi (Labiatae) root, which is a traditional Chinese drug used as an anti-inflammatory and for management of dysmenorrhea.
  
  
  OBJECTIVE
  The effect of wogonin on the uterus has not yet been examined. We investigated the relaxant effects of wogonin on contractile activity of isolated uterine strips of rats.
  
  
  METHODS
  The effect of wogonin on spontaneous uterine contraction, and uterine contraction induced by agonists, K⁺-depolarization and oxytocin in Ca²⁺-free solution was observed. To clarify the type of potassium channel, we tested the effects of 4-aminopyridine, tetraethylammonium and glibenclamide.
  
  
  RESULTS
  Wogonin reduced the contractile amplitude of uterine strip smooth muscle of rats in a dose-dependent manner. The concentration of wogonin for reducing the contraction amplitude by 50% (IC₅₀) on spontaneous contractions was 60.5 μM. Wogonin also inhibited the contraction induced by three agonists (oxytocin, prostaglandin F(2α) and acetylcholine). For the uterine strips pretreated with oxytocin in Ca²⁺-free solution or K⁺-depolarization, wogonin showed relaxant effect on the induced uterine contractions. In addition, whereas the inhibitive effect of wogonin on the contraction of uterine smooth muscle in rats could be partly blocked by 4-aminopyridine and tetraethylammonium, it was not influenced by glibenclamide.
  
  
  CONCLUSIONS
  Wogonin significantly inhibited the contraction of rat uterine smooth muscle probably through the inhibition of the inflow of extracellular calcium into cells via cell membrane, and intracellular release of calcium ions. In addition, the relaxant effect induced by wogonin might be due in part to the opening of voltage-dependent and large conductance Ca²⁺-activated K⁺ channels.
authors.affiliation: School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan.
authors.forename: Huey-Chuan
authors.initials: HC
authors.lastname: Shih
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Yang
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal; D020013:Calcium Signaling / Q000187:drug effects; D002681:China; D004971:Estrus; D020834:Ethnopharmacology; D005260:Female; D044950:Flavanones / Q000302:isolation & purification / Q000494:pharmacology*; D066298:In Vitro Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000819:agonists / Q000037:antagonists & inhibitors; D049990:Membrane Transport Modulators / Q000302:isolation & purification / Q000494:pharmacology*; D009126:Muscle Relaxation / Q000187:drug effects*; D009215:Myometrium / Q000187:drug effects*; D009465:Neuromuscular Agents / Q000302:isolation & purification / Q000494:pharmacology*; D010120:Oxytocics / Q000037:antagonists & inhibitors / Q000494:pharmacology; D018517:Plant Roots / Q000737:chemistry*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000819:agonists / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D031364:Scutellaria baicalensis / Q000737:chemistry*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D044950:Flavanones; D051036:Large-Conductance Calcium-Activated Potassium Channels; D049990:Membrane Transport Modulators; D009465:Neuromuscular Agents; D010120:Oxytocics; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; C085514:wogonin