[Changes in substance P in myocardium and dorsal root ganglion following coronary artery occlusion in rats].

OBJECTIVE

To observe the changes in substance P in myocardium and dorsal root ganglion (DRG) following ligation of the left anterior descending branch of coronary artery. The substance P is commonly considered released mainly from afferent nerve fibers under noxious stimulation and could induce neurogenic inflammation in peripheral tissue.

METHODS

Twenty-four adult male Sprague-Dawley rats, weighing 270-300 g, were randomly divided into four groups: sham-operated group, coronary artery occlusion (CAO) 1 hour group, CAO 3 hours group and CAO 6 hours group, and 6 animals were in each group. The left anterior descending branch of coronary artery was occluded to establish the acute myocardial ischemia model except in the sham-operated group. The myocardium in ischemic and non-ischemic (the contralateral side of ischemic myocardium) region and DRG were harvested as scheduled and processed for immunohistochemistry and for substance P mRNA semi-quantitative examination using reverse transcription-polymerase chain reaction (RT-PCR) technique.

RESULTS

(1) substance P and substance P mRNA levels in myocardium of ischemic areas and myocardium of non-ischemic areas were significantly elevated after CAO compared with sham-operated group (all P<0.05), and they were highest in rats of CAO 3 hours group (all P<0.05). In the myocardium of non-ischemic areas, substance P and substance P mRNA levels were lower than those in myocardium of ischemic areas in CAO groups (all P<0.05). (2) substance P mRNA levels in DRG were significantly elevated after CAO compared with sham-operated group (all P<0.05), and were highest in rats of CAO 3 hours group (both P<0.05).

CONCLUSION

CAO could evoke an increase in substance P in entire myocardium and substance P mRNA expression in DRG in rats, and the results might imply that neurogenic mechanism participates in the pathophysiological changes following myocardial ischemia.