Evidence for the involvement of opioid receptors in ischemic
preconditioning in the rat heart.
Schultz, Jo El J., Elana Rose, Zhenhai Yao, and Garrett J. Gross.
Department of Pharmacology and Toxicology, Medical College of
Wisconsin, Milwaukee, WI 53226, Department of Anesthesia,
Massachusetts General Hospital, Harvard Medical School, Boston,
Massachusetts 02114
APStracts 2:0078H, 1995.
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. Group I: The control (C) group was
subjected to 30 minutes of left coronary artery occlusion and 2 hours
of reperfusion. Group II: Ischemic PC was elicited by 3x 5 minute
occlusion periods interspersed with 5 minutes of reperfusion. Group
III: Naloxone (NL, 3mg/kg, i.v.), a non-selective opioid antagonist,
was given to non-preconditioned rats10 minutes prior to the 30 minute
occlusion period. Group IV and Group V: NL was administered 10
minutes prior to preconditioning (NL + PC) or immediately after the
last 5 minute preconditioning period (PC + NL). Infarct size (IS/AAR)
as a percent of the area at risk (AAR) was determined by 2,3,5
-triphenyltetrazolium chloride staining . PC resulted in a marked
reduction in myocardial infact size from 45+/-5 to 8+/-1 (p<0.05).
Naloxone treatment prior to or immediately after PC abolished this
protective effect; however, naloxone had no effect on infarct size 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.
Received 23 January 1995; accepted in final form 27 February
1995.
APS Manuscript Number H58-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.