title: The involvement of central beta-endorphin in the cardioprotective effects of remote preconditioning mediated by the intracerebroventricular administration of morphine.
abstract: BACKGROUND
  Opioids can mimic the effects of remote cardiac preconditioning and mediate a subsequent reduction in myocardial infarct size.
  
  
  OBJECTIVE
  This study investigated the role of beta-endorphin (β-EP) in intracerebroventricular morphine cardioprotection.
  
  
  METHODS
  Anesthetized, open-chest, male Sprague-Dawley rats were assigned to 1 of 9 treatment groups 3 days after intracerebroventricular catheter placement. Remote preconditioning was induced with 3 μg/kg of morphine. The β-EP antagonist was administered via intracerebroventricular or intravenous routes either 10 min before or immediately after morphine or saline administration. Ischemia-reperfusion injury was caused by 30 min of left coronary artery occlusion followed by 120 min of reperfusion. The infarct size, as a percentage of the area at risk, was determined by 2,3,5-triphenyltetrazolium staining. Radioimmunoassay and immunoreactivity were used to determine the β-EP levels in the serum and brain.
  
  
  RESULTS
  Intracerebroventricular administration of β-EP antiserum (AEP) after morphine administration attenuated the cardioprotective effects of remote preconditioning. The addition of intravenous AEP either before or after morphine did not affect infarct size. After morphine preconditioning, the β-EP level decreased in the hypothalamic arcuate nucleus and increased significantly in the serum, pituitary gland, ventrolateral periaqueductal gray and rostral ventrolateral medulla.
  
  
  CONCLUSIONS
  Central but not peripheral β-EP is involved in morphine remote preconditioning and plays a role in the ongoing mediation of cardioprotective effects.
authors.affiliation: Department of Anesthesiology, First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Shushan, Hefei, China. ch_xq1983@163.com.
authors.forename: X
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Anesthesiology, Second Affiliated Hospital of Anhui Medical University, Hefei, China.
authors.forename: Y E
authors.initials: YE
authors.lastname: Zhang
authors.affiliation: Department of Anesthesiology, First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Shushan, Hefei, China.
authors.forename: X
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Anesthesiology, Third Affiliated Hospital of Anhui Medical University, Hefei, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Pharmacology, Anhui Medical University, Hefei, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000818:Animals; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D009203:Myocardial Infarction / Q000517:prevention & control; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D001615:beta-Endorphin; D009020:Morphine
keywords: Beta-endorphin; Cardioprotection; Intracerebroventricular; Morphine; Remote