title: The relationship between plasma beta-endorphin, opioid receptor activity, and silent myocardial ischemia.
abstract: OBJECTIVE
  To investigate the role of the opioid system in the pathophysiology of silent ischemia through opiate antagonism with naloxone, and to determine the reproducibility of resting and postexercise beta-endorphin levels in predominantly asymptomatic patients with coronary artery disease.
  
  
  METHODS
  Randomized, double-blind, placebo-controlled crossover trial.
  
  
  METHODS
  A University hospital referral center.
  
  
  METHODS
  Ten patients with prior evidence of silent exercise-induced ischemia were studied.
  
  
  METHODS
  An infusion of saline placebo or naloxone at two dose regimens of 0.015 mg/kg or 0.15 mg/kg before supine exercise testing during three separate occasions for each patient.
  
  
  METHODS
  Plasma beta-endorphin was measured at rest, immediately after exercise, and 5 min poststress. Timing and severity of angina and exercise hemodynamics were also determined.
  
  
  RESULTS
  Seven of 10 patients reported no angina, whereas the other three experienced angina with placebo and after administration of naloxone at both doses. The severity and duration of angina was consistently noted to decrease in these patients after naloxone administration, especially after low-dose naloxone relative to placebo. There were no apparent correlations between beta-endorphin levels and the characteristics of angina in these three patients, nor between beta-endorphin and hemodynamic responses in all patients in the study.
  
  
  CONCLUSIONS
  (a) naloxone failed to precipitate angina in this population of patients with silent ischemia; (b) naloxone appears to exert an analgesic effect at low doses; and (c) a variability of 5 pM at rest and 13 pM after exercise might be expected in predominantly asymptomatic patients due to random variation, which is comparable with results found in normal subjects.
authors.affiliation: Department of Cardiology, University of North Carolina School of Medicine, Chapel Hill.
authors.forename: A C
authors.initials: AC
authors.lastname: Seña
authors.forename: W
authors.initials: W
authors.lastname: Maixner
authors.forename: M N
authors.initials: MN
authors.lastname: Ballenger
authors.forename: M C
authors.initials: MC
authors.lastname: Herbst
authors.forename: G
authors.initials: G
authors.lastname: Koch
authors.forename: D S
authors.initials: DS
authors.lastname: Sheps
mesh_terms: D000368:Aged; D000787:Angina Pectoris / Q000097:blood / Q000503:physiopathology; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000097:blood / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology / Q000523:psychology; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D015203:Reproducibility of Results; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D001615:beta-Endorphin