丘脑中央下核和顶盖前区前核分别参与介导强电针和弱电针的镇痛效应

THALAMIC NUCLEUS SUBMEDIUS AND ANTERIOR PRETECTAL NUCLEUS MEDIATE THE INHIBITION OF SPINAL NOCICEPTIVE TRANSMISSION BY ELECTRO ACUPUNCTURE WITH HIGH AND LOW INTENSITIES

在大鼠以强电刺激外周感受野诱发的脊髓背角ＷＤＲ和ＮＳ神经元的晚串放电（Ｃ－反应）作为伤害感受性反应，观察了双侧丘脑中央下核（Ｓｍ）或顶盖前区前核（ＡＰｔＮ）内微量注射局麻药利多卡因对不同强度电针引起的镇痛效应的影响。结果表明：双侧Ｓｍ局麻可明显减弱强电针对Ｃ－反应的抑制效应，但对弱电针的抑制效应无明显影响；双侧ＡＰｔＮ局麻可明显减弱弱电针对Ｃ－反应的抑制效应，但对强电针的抑制效应无明显影响。结果提示，不同强度的电针刺激可能由粗细不同的纤维传入，通过不同的中枢机制产生镇痛作用。Ｓｍ参与介导强电针兴奋细纤维产生的镇痛作用；ＡＰｔＮ则参与介导弱电针兴奋粗纤维产生的镇痛作用。

Single wide dynamic range(WDR) and nociceptive specific (NS) neurons were recorded extracellularly in the dorsal horn of the rat lumbar spinal cord. The late train discharges (C fiber evoked response) of the neurons elicited by intense electrical stimulation of the skin were taken as a nociceptive response. The effect of bilateral microinjection of a local anesthetic,lidocaine (2%,0.5 μl),into the thalamic nucleus submedius(Sm) or the anterior pretectal nucleus(APtN) on the inhibition produced by the EA of different intensities applied to the “Tsusanli point”(St.36) was observed. The results indicated that inactivation of bilateral Sm reduced the inhibitory effect of high intensity EA but not that of low intensity EA on the nociceptive response of spinal neurons.However,inactivation of bilateral APtN attenuated the inhibitory effect of low intensity EA but not that of high intensity EA on the nociceptive response of spinal neurons.It is suggested that the analgesic effects of EA with different intensities resulted from activation of different groups of afferent fibers and were mediated by different central mechanisms.The antinociception elicited by high intensity EA was produced by activation of small afferent fibers and mediated,at least in part,by the Sm.On the other hand,the antinociception produced by low intensity EA resulted from activation of large afferent fibers and was mediated,at least in part,through the APtN.