Evidence for involvement of opioid receptors in ischemic preconditioning in rat hearts.
The purpose of the present study was to investigate a possible role of opioid receptors in ischemic preconditioning (PC). To test this hypothesis, anesthetized, open-chest, male Wistar rats were subjected to five different protocols. In group I, the control group was subjected to 30 min of left coronary artery occlusion and 2 h of reperfusion. In group II, ischemic PC was elicited by three 5-min occlusion periods interspersed with 5 min of reperfusion. In group III, naloxone (NL, 3 mg/kg iv), a nonselective opioid antagonist, was given to nonpreconditioned rats 10 min before the 30-min occlusion period. Finally, NL was administered 10 min before preconditioning (NL + PC, group IV) or immediately after the last 5-min preconditioning period (PC + NL, group V). Infarct size (IS) as a percentage of the area at risk (AAR) (IS/AAR) was determined by 2,3,5-triphenyltetrazolium chloride staining. PC resulted in a marked reduction in myocardial IS from 45 +/- 5 to 8 +/- 1 (P < 0.05). NL treatment before or immediately after PC abolished this protective effect; however, NL had no effect on IS in non-PC rats. These results are the first to support the hypothesis that activation of opioid receptors may play an important role in ischemic PC in the rat myocardium.
Schultz
J E
JE
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226, USA.
Rose
E
E
Yao
Z
Z
Gross
G J
GJ
D000818:Animals; D006321:Heart / Q000503:physiopathology*; D006439:Hemodynamics; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000517:prevention & control; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015425:Myocardial Reperfusion; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000502:physiology*; D012307:Risk Factors
D011957:Receptors, Opioid; D009270:Naloxone