Effects of intrathecal morphine remote preconditioning on Akt/eNOS signaling pathways and myocardial apoptosis in rats

Abstract

Objective To investigate the effects of intrathecal morphine remote preconditioning (MRPC) on protein-serine-threonine kinases-endothelial nitric oxide synthase (Akt/eNOS) signaling pathways and cardiac myocyte apoptosis in rats.Methods Male SD rats weighing 280-320 g were used in this study.A needle was inserted through a surgically created hole into the sub-dural space of spinal cord.Thirty-six rats in which intrathecal needle was successfully placed without complication were randomly divided into 3 groups (n =12 in each).In group Ⅰ sham operation was performed (Sham).In group Ⅱ myocardial I/R was produced (I/R).In group Ⅲ morphine was given intrathecally in 3 repeated doses of 1 μg/kg at 5 min intervals before ischemia (MRPC).Myocardial I/R was produced by occlusion of left anterior descending branch (LAD) of coronary artery for 30 min followed by 120 min reperfusion.The animals were then sacrificed and hearts removed for measurement of area at risk (AAR) and infarct size area (IS).IS/AAR ratio was calculated.Myocardial apoptosis was detected by TUNEL and apoptotic index (the number of apoptotic myocardial cells/the total number of myocardial cells) was calculated.The levels of Akt,phosphorylated Akt (p-Akt) and eNOS was determined by Western blot.Results The infarct size,myocardial cell apoptotic index and pAkt level were higher and eNOS level was significantly lower in I/R group than those in group Sham (P ＜ 0.01).MRPC significantly reduced the infarct size and myocardial cell apoptotic index,and pAkt and eNOS level up-regulated in group RMPC compared with group I/R (P ＜ 0.01).Conclusions Akt/eNOS signaling pathways probably participate in the protective effects of intrathecal morphine remote preconditioning against myocardial I/R injury and myocardial cell apoptosis in rats. Key words: Morphine; Intrathecal; Remote preconditioning; Myocardial reperfusion injury; Protein-serine-threonine kinases