Abstract： Objective To investigate the expression of tumor necrosis factor-α (TNF-α) in lungs following coronary artery occlusion (CAO) and the effect of morphine pretreatment via epidural administra-tion on its expression in the rats. Methods Eighteen adult healthy male Sprague-Dawley (SD) rats were randomly divided into sham operation group (S group), CAO group and morphine pretreatment group (M group), with 6 in each group. In S group the left anterior descending branch of coronary artery was not occluded. In CAO group the left anterior descending branch of coronary artery was occluded. In M group the rats were pre-treated with morphine 60 μg/kg by epidural injection 15 minutes before CAO. The right lung was harvested 3 hours after CAO. The expression of TNF-α in lungs was assessed with immuno-histochemistry and enzyme linked immunosorbent assay (ELISA). Results The immunohistochemistry results showed, compared with S group (8. 68±0. 29, 1. 609 ± 0. 050), the positive unit and average light density of TNF-α in CAO group (24. 55±6. 25, 1. 844±0. 027) and M group (11.60±1.21, 1. 733±0. 027) were higher significantly, while they were lower significantly in M group compared with CAO group (all P<0. 01). ELISA results showed the level of TNF-α in the lung was significantly higher in CAO group [(221.58±5. 23) ng/L] and M group [(103. 45±4. 56) ng/L] than that in S group [(47. 14±1.36) ng/L],while it was significantly lower in M group compared with CAO group (all P<0. 01). Conclusion Acute myocardial ischemia could cause up-regulation of TNF-a in lungs, which is likely to be mediated by neural mechanisms. Opioid and its receptors in spinal cord might be involved in modulation of inflammatory reaction in the lung after acute coronary ischemia.