兴奋黑质对中缝大核神经元的抑制作用及其机制

本工作观察到在清醒、麻痹大鼠,电刺激黑质致密部(SN_C)或网状部(SN_R)均明显抑制中缝大核(NRM)神经元的自发放电;电针刺激双侧“足三里-三阴交”的同时,电刺激SN_C或SN_R可完全翻转电针对NRM神经元的兴奋效应,NRM神经元放电受抑制。将谷氨酸钠微量注入黑质,对中缝大核神经元亦具有抑制作用,电解损毁双侧中脑导水管周围灰质(PAG)腹外侧部或将多巴胺受体阻断剂氟哌啶醇注入该处,均可阻断此抑制效应。提示黑质对抗电针镇痛机制之一是通过其DA能投射纤维作用于PAG内的DA受体,进而抑制PAG-NRM系统而实现的。

INHIBITORY EFFECT OF SUBSTANTIA NIGRA-STIMULATION ON NEURONAL ACTIVITY OF NUCLEUS RAPHE MAGNUS AND ITS MECHANISM

In conscious curarized and artificially ventilated rat, electrical stimulation ofthe zona compacta (SNc) or zona reticulata substantia nigra (SN_R) markedlysuppressed spontaneous unit discharges of the nucleus raphe magnus. Whenelectroacupuncture (delivered to "Zusali-Sanyingiao" acupoints) was combinedwith electrical stimulation of SN_C or SN_R, the excitatory effect of electroacupunctureon NRM was entirely reversed and the spontaneous unit discharge of NRM wassuppressed. Microinjection of sodium glutamate into SN also inhibited NRMneurons. This effect was blocked by bilateral injection of haloperidol into theventrolateral parts of the periaqueductal gray matter (PAG) or by electrical lesionsof the same PAG areas. These results suggest that one of the mechanisms underly-ing the antagonist effect of SN on acupuncture analgesia is due to the inhibitionof PAG-NRM analgesic system by th e SN dopaminergic neurons.