title: alpha 1-adrenoceptor stimulation is able to reverse halothane-induced cardiac depression in isolated rat hearts.
abstract: BACKGROUND
  Stimulation of myocardial alpha 1-adrenoceptors has been shown to exert positive inotropic effects through a cyclic AMP-independent mechanism. The purpose of this study was to examine if alpha 1-adrenoceptor stimulation is able to attenuate myocardial depression produced by exposure to halothane, and to test if alpha 1-adrenoceptor stimulation alters myocardial oxygen supply-demand balance in hearts exposed to halothane.
  
  
  METHODS
  The effects of phenylephrine were examined in 7 isolated perfused rat hearts. Variables measured were: heart rate, isovolumetric peak left ventricular pressure (LVP), LV dP/dt, coronary arterial flow, myocardial O2 delivery (DO2), myocardial O2 consumption (MVO2) and the ratio of DO2/MVO2. Each heart was exposed to phenylephrine cumulatively 0.1 microM, 0.3 microM, 1 microM and 3 microM under the administration of 1% halothane in the presence of propranolol 1 microM.
  
  
  RESULTS
  Halothane 1% decreased the heart rate by 9 +/- 3%, LVP by 37 +/- 3%, and LV dP/dt by 35 +/- 2%. Phenylephrine restored these decreases to the baseline levels. Phenylephrine maintained or further enhanced the reductions in coronary flow and DO2 produced by halothane, resulting in a decrease in the DO2/ MVO2 ratio.
  
  
  CONCLUSIONS
  alpha 1-adrenoceptor stimulation is capable of restoring direct cardiac depressant effects of halothane with a possible impairment of the oxygen supply-demand balance.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Kyuslm University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Okuyama
authors.forename: S
authors.initials: S
authors.lastname: Hoka
authors.forename: H
authors.initials: H
authors.lastname: Okamoto
authors.forename: T
authors.initials: T
authors.lastname: Kawasaki
authors.forename: K
authors.initials: K
authors.lastname: Yamaura
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003326:Coronary Circulation / Q000187:drug effects; D003864:Depression, Chemical; D006221:Halothane / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*
chemical_list: D018685:Anesthetics, Inhalation; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D002118:Calcium; D006221:Halothane