title: Effect of histamine on phasic and tonic contractions of isolated uterine tissue from pregnant women.
abstract: OBJECTIVE
  To enhance our understanding of the uterotonic effect of histamine, we compared the effects of histamine on spontaneous phasic and tonic contractile activity of uterine strips from term pregnant nonlaboring women.
  
  
  METHODS
  Longitudinal uterine strips were used from the lower uterine segment of term pregnant nonlaboring women undergoing elective cesarean section. The concentration-response relationship to histamine (10(-8) to 10(-4) mol/L) was determined in spontaneously contracting strips or in strips contracted tonically with a protein kinase C activator (-)-indolactam V in the presence of H(1) receptor antagonist (S[+]-chlorpheniramine maleate), H(2) receptor antagonist (cimetidine), or solvent.
  
  
  RESULTS
  Histamine increased spontaneous phasic myometrial contractions in a concentration-dependent manner. H(1), but not H(2), receptor antagonist significantly attenuated the response to histamine. Histamine significantly reduced tonic contractions of uterine strips induced by indolactam V. H(1) histamine receptor antagonist abolished relaxation, whereas H(2) histamine receptor antagonist had no effect.
  
  
  CONCLUSIONS
  Histamine increases spontaneous, but inhibits tonic, contractions of uterine strips from term pregnant nonlaboring women. Both effects are mediated through activation of H(1) receptors.
authors.affiliation: Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Tex 77555, USA.
authors.forename: Egle
authors.initials: E
authors.lastname: Bytautiene
authors.forename: Yuri P
authors.initials: YP
authors.lastname: Vedernikov
authors.forename: George R
authors.initials: GR
authors.lastname: Saade
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.forename: Robert E
authors.initials: RE
authors.lastname: Garfield
mesh_terms: D002744:Chlorpheniramine / Q000494:pharmacology; D002927:Cimetidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006632:Histamine / Q000008:administration & dosage / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007769:Lactams / Q000494:pharmacology; D009994:Osmolar Concentration; D011247:Pregnancy / Q000502:physiology*; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects
chemical_list: D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D007211:Indoles; D007769:Lactams; D002744:Chlorpheniramine; D002927:Cimetidine; D006632:Histamine; C043969:indolactam V