| Objective:The purpose of this study was to investigate changes of OFQ in dorsal root ganglia(DRG),spinal cord,heart and intestine and the mechanisms of the changes following acute myocardial ischemia evoked by coronary artery occlusion(CAO)in rats.The intervention effects of pre-treatment with morphine,ropivacaine and esmolol were studied.Methods:The experiments were carried out in two steps.In step one,adult male SD rats were randomly devided into three groups:Control group(group C),the samples were harvested directly from the rats under anaesthesia;Sham group(group S),with the same scheme of surgery without CAO;Coronary artery occlusion group(group CAO),with the left anterior descending branch of coronary artery occluded under general anaesthesia.Then group S and group CAO were further devided into four subgroups:group CAO0.5h,group CAO1h,group CAO3h and group CAO6h.Then rats were killed as scheduled at different time points,and the samples were collected for immunohistochemistry(IHC).The expressions of OFQ in DRG, spinal cord,myocardium and intestine of the rats were examined,and the expression of preproOFQ mRNA in DRG and spinal cord compared with subgroups after CAO.In step two of the experiments,the time point of highest expression of OFQ after CAO was chosen respectively for interventional study according to the results of step one experiment. Adult male SD rats were randomly devided into six groups:Group S(Sham group),Group CAO(Coronary artery occlusion group),Group I-M(Intravenous injection Morphine group), group I-E(Intravenous injection Esmolol group),Group E-M(Epidural Morphine group)and Group E-R(Epidural Ropivacaine group).Rats were pre-treated with 1.25mg.kg-1of morphine in group I-M;3.0mg.kg-1of esmolol in group I-E through caudal vein and 60μg.kg-1of Morphine and 1%Ropivacaine 120μg.kg-1Epidurally 15 minutes before CAO.Then rats were killed as scheduled,and the samples were collected for immunohistochemistry(IHC),ELISA and Real Time RT-PCR.Results:(1)The expressions of OFQ in spinal cord,DRG,myocardium and intestine were significantly increased after CAO compared with the controls(p＜0.05).The expression of OFQ in myocardium peaked at 3h of CAO while OFQ in DRG and spinal cord peaked at 1h of CAO.There was no significant difference in expressions of OFQ between ischemic myocardium and non-ischemic myocardium.The expression of OFQ in dorsal spinal cord was significantly higher than that in ventral spinal cord after CAO.The expression of OFQ decreased significantly in Group I-M,I-E,E-M and E-R compared with the CAO Group.There was no significant difference among the interventional groups.(2)The expression of preproOFQ mRNA in spinal cord and DRG decreased significantly after CAO as compared with the baseline in the control group(p＜0.05)except CAO1h.It decreased significantly in the interventional groups compared with Group CAO(p＜0.05),And there was no significant differences among the interventional groups.Conclusions:(1)Coronary artery occlusion could cause significant increase of OFQ in spinal cord,DRG,myocardium and intestine of rats.It may demonstrate that acute myocardial ischemia,as a nociceptive stimulus,activated the neurogenic reactions and OFQ might play a role in the process.(2)Neural mechanism was involved in the reaction and(3)opioid and adenergic mechanisms may be involved in the neurogenic reaction.OFQ may serve as a transmitter of the reaction after CAO.Further investigation on the subject is invited.
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