title: Biphasic manner of melittin on isolated guinea pig atria.
abstract: OBJECTIVE
  To investigate the effect of melittin (Mel) on isolated guinea pig atria.
  
  
  METHODS
  The effect of Mel on the contraction and heart rate of isolated guinea pig atria at different concentrations was determined.
  
  
  RESULTS
  Mel at a lower concentration (0.1-0.8 mumol.L-1) enhanced the contraction of left atria in a concentration-dependent manner; but at a higher concentration (1.6-12.8 mumol.L-1) it exerted an inhibitory effect. At 0.1-30 mumol.L-1 it was found to increase heart rate of right atria. In addition, verapamil (Ver) 0.3 mumol.L-1 was found to depress the effect of Mel.
  
  
  CONCLUSIONS
  Mel possesses a biphasic effect on left atria and a positive chronotropic effect on right atria. Its mechanism might be related with Ca2+ channel.
authors.affiliation: Department of Pharmacology, School of Pharmacy, Shanghai Medical University, Shanghai 200032, China. mhjiang@shmu.edu.cn
authors.forename: S
authors.initials: S
authors.lastname: Yang
authors.forename: J E
authors.initials: JE
authors.lastname: Liu
authors.forename: A Z
authors.initials: AZ
authors.lastname: Zhang
authors.forename: M H
authors.initials: MH
authors.lastname: Jiang
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006325:Heart Atria; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D008555:Melitten / Q000494:pharmacology*; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D008555:Melitten; D014700:Verapamil