去甲肾上腺素对吗啡依赖大鼠中枢痛觉的调制

Modulation of norepinephrine in the central painful sense in morphine-dependent rats

目的研究去甲肾上腺素(NE)和酚妥拉明对吗啡依赖大鼠伏核(NAc)内痛兴奋神经元(PENs)和痛抑制神经元(PINs)生物电活动的影响。方法采用NAc内给药的方法,以电脉冲刺激右侧的坐骨神经作为伤害性刺激,用玻璃微电极记录吗啡依赖大鼠NAc内PENs或PINs的电变化。结果 NAc内微量注入NE(4 g.L-1,0.5μl)可使吗啡依赖大鼠NAc中PEN对伤害性刺激反应的痛诱发放电频率减少,潜伏期延长,但PIN痛诱发放电频率增加,抑制时程(ID)缩短,呈现出NE的镇痛效应。NAc内注入酚妥拉明(4g.L-1,0.5μl)产生相反反应,表明酚妥拉明可阻断内源性NE的作用。结论 NE和α-肾上腺素能受体均参与吗啡依赖大鼠NAc内伤害性信息的调控。NAc是调制吗啡依赖大鼠中枢痛觉的重要核团之一。

Aim To investigate the effects of norepinephrine（NE） and phentolamine on the bioelectrical activities of pain-excited neurons（PENs） and pain-inhibited neurons（PINs） in the nucleus accumbens（NAc） of the morphine-dependent rats.Methods Drugs were injected into NAc.Trains of electric pulses applied to the right sciatic nerve were used to provide noxious stimulation.The electrical changes of PENs or PINs in NAc of the morphine-dependent rats were recorded by a glass microelectrode.Results Intra-NAc microinjection of NE（4 g·L^-1,0.5 μl） decreased the pain-evoked discharge frequency of PEN and prolonged the PEN latency,but increased the pain-evoked discharge frequency of PIN and shortened the PIN inhibitory duration（ID） in the NAc of the morphine-dependent rats,exhibiting the analgesic effect of NE.Intra-NAc administration of phentolamine（4 g·L^-1,0.5 μl） produced opposite responses,suggesting that phentolamine could block the effect of endogenous NE.Conclusions NE and α-adrenergic receptor are involved in the modulation of nociceptive information transmission in the NAc of the morphine-dependent rats.NAc is an important nucleus of central pain modulation in morphine-dependent rats.