Effects of clonidine on visceral pain induced by acute myocardial ischemia in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of clonidine on the visceral pain induced by acute myocardial ischemia. Methods Male SD rats weighing 250-280 g were operated upon under general anesthesia with intraperitoneal methane 1.2 g/kg and local infiltration of the skin incision. After tracheal intubation, the animals were mechanically ventilated (VT = 5-7 ml/kg, RR = 75 bpm). The anterior descending branch of left coronary artery was occluded with a snare through the left 4 th intercostal space. The animals were then fastened to a brain stereotaxic instrument and a burr hole was made in the skull. A glass micro-electrode was inserted into the brain. The discharges of noxious stimulation responding neuron (NSRN) in parafascicular nucleus were recorded. Twenty-four rats detected NSRN showed response to coronary artery occlusion (CAO) were randomly divided into 4 groups (n =6 each) group Ⅰ CAO + normal saline 0.1 ml; group Ⅱ CAO + elonidine 30 μg; group Ⅲ CAO + clanidine 100 μg; group Ⅳ CAO + clonidine 100 μg + yohimbine (an α2-adrenergic receptor antagonist) 200 μg. In group Ⅳ , clonidine was administered intravenously 15 min after CAO, and then yohimbine was injected intravenously 15 min later. The discharges of NSRN were recorded every 5 min for 60 min from the beginning of CAO. Results Clonidine 100 μg significantly inhibited the increased frequency of nociceptive discharge rate of NSRN after CAO. However, this effect could be blocked by the α2-adrenergic receptor antagonist yohimbine.Conclusion Clonidine 100 μg can reduce the visceral pain induced by acute myocardial ischemia through activiting α2-adrenergic receptor.