Adenosine and opioid receptors do not trigger the cardioprotective effect of mild hypothermia.

Abstract

Mild hypothermia (32°C-34°C) exerts a potent cardioprotection in animal models of myocardial infarction. Recently, it has been proposed that this beneficial effect is related to survival signaling. We, therefore, hypothesized that the well-known cardioprotective pathways dependent on adenosine and/or opioid receptors could be the trigger of hypothermia-induced salvage. Open-chest rabbits were accordingly exposed to 30 minutes of coronary artery occlusion (CAO) under normothermic (NT) or hypothermic ([HT] 32°C) conditions. In the latter, hypothermia was induced by total liquid ventilation with temperature-controlled perfluorocarbons in order to effect ultrafast cooling and to accurately control cardiac temperature. After 4 hours of reperfusion, infarct and no-reflow zone sizes were assessed and quantified as a percentage of the risk zone. In animals experiencing HT ischemia, the infarct size was dramatically reduced as compared to NT animals (9% ± 3% vs 55% ± 2% of the risk zone, respectively). Importantly, administration of opioid and adenosine receptor antagonists (naloxone [6 mg/kg iv] and 8-(p-sulfophenyl) theophylline [20 mg/kg iv], respectively) did not alter the infarct size or affect the cardioprotective effect of hypothermia. Doses of these 2 antagonists were appropriately chosen since they blunted infarct size reduction induced by selective opioid or adenosine receptor stimulation with morphine (0.3 mg/kg iv) or N (6)-cyclopentyladenosine ([CPA] 100 μg/kg iv), respectively. Therefore, the cardioprotective effect of mild hypothermia is not triggered by either opioid or adenosine receptor activation, suggesting the involvement of other cardioprotective pathways.

• Authors: Lys Darbera, Mourad Chenoune, Fanny Lidouren, Bijan Ghaleh, Michael V Cohen, James M Downey, Alain Berdeaux, Renaud Tissier
• Journal: Journal of cardiovascular pharmacology and therapeutics (J Cardiovasc Pharmacol Ther) Vol. 17 Issue 2 Pg. 173-80 (Jun 2012) ISSN: 1940-4034 [Electronic] United States
• PMID: 21725026 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Analgesics, Opioid
• Fluorocarbons
• Narcotic Antagonists
• Purinergic P1 Receptor Antagonists
• Receptors, Opioid
• Receptors, Purinergic P1
• Naloxone
• N(6)-cyclopentyladenosine
• Morphine
• 8-(4-sulfophenyl)theophylline
• Theophylline
• Adenosine

Topics

• Adenosine (analogs & derivatives, pharmacology)
• Analgesics, Opioid (pharmacology)
• Animals
• Fluorocarbons (chemistry)
• Hypothermia, Induced (methods)
• Morphine (pharmacology)
• Myocardial Infarction (physiopathology, therapy)
• Naloxone (pharmacology)
• Narcotic Antagonists (pharmacology)
• Purinergic P1 Receptor Antagonists (pharmacology)
• Rabbits
• Receptors, Opioid (drug effects, metabolism)
• Receptors, Purinergic P1 (drug effects, metabolism)
• Theophylline (analogs & derivatives, pharmacology)
• Time Factors