Waszczak B L, Lee E K, Ferraro T, Hare T A, Walters J R
Brain Res. 1984 Jul 23;306(1-2):307-18. doi: 10.1016/0006-8993(84)90380-9.
Many of the behavioral consequences of dopamine system activation are thought to be mediated by substantia nigra pars reticulata output pathways. Extracellular, single unit recording studies were conducted to determine how i.v. administration of the dopamine agonist, apomorphine, affects the activity of these pars reticulata neurons. Results revealed that a 320 micrograms/kg dose of the drug, considered sufficient to stimulate striatal postsynaptic dopamine receptors, caused highly variable changes in reticulata cell firing. Cells exhibited increases, decreases, or no changes in firing. Many cells also displayed marked minute to minute changes in firing. This non-uniform pattern of responses was not related to state of consciousness since similar responses were observed in both chloral hydrate-anesthetized as well as conscious, paralyzed rats. Both the increases and decreases could be reversed by subsequent administration of haloperidol. The variable responses to apomorphine were reduced but not totally prevented by striatal kainic acid lesions, suggesting that changes in striatonigral transmission may account for some but not all of the firing changes which were observed. A lower dose of apomorphine (20 micrograms/kg), thought to act primarily at dopamine cell autoreceptors, had little effect on reticulata cell firing and did not modify the variable responses normally observed after the higher dose. These results contrast strikingly with the consistent excitatory responses to apomorphine which have previously been observed in the globus pallidus and suggest that complex or multiple indirect effects of the drug may contribute to the varied reticulata responses.
多巴胺系统激活的许多行为后果被认为是由黑质网状部输出通路介导的。进行了细胞外单单位记录研究，以确定静脉注射多巴胺激动剂阿扑吗啡如何影响这些网状部神经元的活动。结果显示，320微克/千克剂量的该药物被认为足以刺激纹状体突触后多巴胺受体，可引起网状部细胞放电高度可变的变化。细胞放电表现为增加、减少或无变化。许多细胞的放电在每分钟内也有明显变化。这种不均匀的反应模式与意识状态无关，因为在水合氯醛麻醉的大鼠以及清醒、瘫痪的大鼠中都观察到了类似的反应。增加和减少的反应都可被随后给予的氟哌啶醇逆转。纹状体内注射 kainic 酸损伤后，对阿扑吗啡的可变反应有所减少，但并未完全消除，这表明纹状体黑质传递的变化可能是所观察到的一些但不是所有放电变化的原因。较低剂量的阿扑吗啡（20微克/千克）被认为主要作用于多巴胺细胞自身受体，对网状部细胞放电几乎没有影响，也不会改变高剂量后通常观察到的可变反应。这些结果与之前在苍白球中观察到的对阿扑吗啡一致的兴奋反应形成了鲜明对比，表明该药物的复杂或多种间接作用可能导致了网状部的不同反应。
