Evinger C, Basso M A, Manning K A, Sibony P A, Pellegrini J J, Horn A K
Department of Neurobiology and Behavior, State University of New York, Stony Brook 11794.
Exp Brain Res. 1993;92(3):507-15. doi: 10.1007/BF00229040.
In humans and rats we found that nicotine transiently modifies the blink reflex. For blinks elicited by stimulation of the supraorbital branch of the trigeminal nerve, nicotine decreased the magnitude of the orbicularis oculi electromyogram (OOemg) and increased the latency of only the long-latency (R2) component. For blinks elicited by electrical stimulation of the cornea, nicotine decreased the magnitude and increased the latency of the single component of OOemg response. Since nicotine modified only one component of the supraorbitally elicited blink reflex, nicotine must act primarily on the central nervous system rather than at the muscle. The effects of nicotine could be caused by direct action on lower brainstem interneurons or indirectly by modulating descending systems impinging on blink interneurons. Since precollicular decerebration eliminated nicotine's effects on the blink reflex, nicotine must act through descending systems. Three lines of evidence suggest that nicotine affects the blink reflex through the basal ganglia by causing dopamine release in the striatum. First, stimulation of the substantia nigra mimicked the effects of nicotine on the blink reflex. Second, haloperidol, a dopamine (D2) receptor antagonist, blocked the effect of nicotine on the blink reflex. Third, apomorphine, a D2 receptor agonist, mimicked the effects of nicotine on the blink reflex.
在人类和大鼠中，我们发现尼古丁会短暂改变瞬目反射。对于由三叉神经眶上支刺激引发的眨眼，尼古丁降低了眼轮匝肌肌电图（OOemg）的幅度，并仅增加了长潜伏期（R2）成分的潜伏期。对于由角膜电刺激引发的眨眼，尼古丁降低了OOemg反应单一组分的幅度并增加了潜伏期。由于尼古丁仅改变了眶上引发的瞬目反射的一个成分，尼古丁必定主要作用于中枢神经系统而非肌肉。尼古丁的作用可能是通过直接作用于脑桥下部的中间神经元，或间接通过调节作用于眨眼中间神经元的下行系统而产生的。由于脑桥前脑去大脑术消除了尼古丁对瞬目反射的影响，尼古丁必定是通过下行系统起作用的。有三条证据表明尼古丁通过导致纹状体中多巴胺释放，经基底神经节影响瞬目反射。第一，刺激黑质可模拟尼古丁对瞬目反射的作用。第二，氟哌啶醇，一种多巴胺（D2）受体拮抗剂，可阻断尼古丁对瞬目反射的作用。第三，阿扑吗啡，一种D2受体激动剂，可模拟尼古丁对瞬目反射的作用。
