title: [Naloxone suppresses ischemic arrhythmias via potentiating baroreflex].
abstract: OBJECTIVE
  To study the relationship between the anti-arrhythmia action of naloxone (Nal) and its effect on baroreflex sensitivity (BRS).
  
  
  METHODS
  Acute myocardial infarction was produced by ligating coronary artery in Sprague-Dawley rats. Ventricular extrasystole (VE), tachycardia (VT), and fibrillation (VF) were recorded on ECG. The slopes of linear regression (b) from systolic blood pressure and cardiac cycle after intravenous injection (i.v.) of phenylephrine 2 micrograms was taken as the BRS. The area of infarct was estimated after TTC staining.
  
  
  RESULTS
  Nal 0.5 mg i.v., intracisternal injection (i.c.) of Nal 0.1 mg, and i.c. beta-endorphin (beta-End) antiserum 10 microL suppressed the ischemic arrhythmias, arrhythmia score was 1.8 +/- 1.1 (Nal i.v.) vs 3.8 +/- 2.1 (Saline i.v.); 1.7 +/- 1.5 (Nal i.c.) vs 4.0 +/- 2.6 (Artificial CSF i.c.) and 1.7 +/- 1.6 (beta-End antiserum i.c.) vs 4.1 +/- 2.0 (Serum i.c.) (P < 0.05) and potentiated the BRS, BRS was 4.2 +/- 1.8 (Nal i.v.) vs 2.9 +/- 0.8 (saline i.v.); 4.5 +/- 1.7 (Nal i.c.) vs 2.8 +/- 0.7 (Artificial CSF i.c.) and 4.4 +/- 1.1 (beta-End antiserum i.c.) vs 3.0 +/- 0.9 (Serum i.c.) (P < 0.05). BRS showed negative relations to the arrhythmia scores with r of -0.69 for i.v Nal, -0.72 for i.c. Nal, and -0.67 for i.c. beta-End antiserum (P < 0.05).
  
  
  CONCLUSIONS
  Nal suppressed ischemic arrhythmias via antagonization of beta-endorphin and potentiation of BRS.
authors.affiliation: Cardiovascular Department, Affiliated Renji Hospital, Shanghai Second Medical University, China.
authors.forename: B
authors.initials: B
authors.lastname: He
authors.forename: D S
authors.initials: DS
authors.lastname: Zheng
authors.forename: S H
authors.initials: SH
authors.lastname: Zhang
authors.forename: C H
authors.initials: CH
authors.lastname: Wang
authors.forename: B C
authors.initials: BC
authors.lastname: Lin
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D017704:Baroreflex / Q000187:drug effects*; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D009203:Myocardial Infarction / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000276:immunology
chemical_list: D000889:Anti-Arrhythmia Agents; D007106:Immune Sera; D009270:Naloxone; D001615:beta-Endorphin