Morphine induces preconditioning via activation of mitochondrial KCa channels |
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Authors: | Jan Fräßdorf MD Ragnar Huhn MD PhD Corinna Niersmann MD Nina C. Weber PhD Wolfgang Schlack MD Benedikt Preckel MD Markus W. Hollmann MD PhD |
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Affiliation: | 1. Department of Anesthesiology, Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 2. University Hospital, Duesseldorf, Germany 3. Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany
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Abstract: | Purpose Mitochondrial calcium sensitive potassium (mKCa) channels are involved in cardioprotection induced by ischemic preconditioning. In the present study we investigated whether morphine-induced preconditioning also involves activation of mKCa channels. Methods Isolated rat hearts (six groups; each n = 8) underwent global ischemia for 30 min followed by a 60-min reperfusion. Control animals were not further treated. Morphine preconditioning (MPC) was initiated by two five-minute cycles of morphine 1 μM infusion with one five-minute washout and one final ten-minute washout period before ischemia. The mKCa blocker, paxilline 1 μM, was administered, with and without morphine administration (MPC + Pax and Pax). As a positive control, we added an ischemic preconditioning group (IPC) alone and combined with paxilline (IPC + Pax). At the end of reperfusion, infarct sizes were determined by triphenyltetrazoliumchloride staining. Results Infarct size was (mean ± SD) 45 ± 9% of the area at risk in the Control group. The infarct size was less in the morphine or ischemic preconditioning groups (MPC: 23 ± 8%, IPC: 20 ± 5%; each P < 0.05 vs Control). Infarct size reduction was abolished by paxilline (MPC + Pax: 37 ± 7%, P < 0.05 vs MPC and IPC + Pax: 36 ± 6%, P < 0.05 vs IPC), whereas paxilline alone had no effect (Pax: 46 ± 7%, not significantly different from Control). Conclusion Cardioprotection by morphine-induced preconditioning is mediated by activation of mKCa channels. |
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