大鼠脑干向三叉神经脊束核尾侧亚核浅层的神经减压素能和脑啡肽能投射

NEUROTENSINERGIC AND ENKEPHALINERGIC PROJECTIONS FROM THE BRAINSTEM TO THE CAUDAL SUBNUCLEUS OF THE SPINAL TRIGEMINAL NUCLEUS IN THE RAT

本研究用荧光金（FG）逆行追踪与免疫荧光组织化学杂色相结合技术对大鼠脑干向三叉神经脊束核尾侧亚核（Vc）的NT能和L－ENK能投射进行了观察．脑干向Vc发出NT能和L－ENK能投射的神经元主要位于中脑导水管周围灰质、中缝大核、巨细胞同状核α部和延髓中继核簇．结果提示NT和ENK可能参与下行抑制系统，Vc浅层密集的ENK样阳性终末不仅来自Vc内的局部或中间神经元，而且来自下行抑制系统的起始核团和脑干的其它结构，这些广泛起源的NT和L－ENK能投射可能对Vc浅层内传送面口部伤害性刺激信息的神经元和中间种经元发挥抑制和／或去抑制作用，调控面口部伤害性刺激信息向中枢传递．

It is generally accepted that the caudal subnucleus of the spinal trigeminal nucleus (Vc) plays an irnportant role in both transmitting and regulating nociceptive information frorn orofacial region. Many structures within the brainstem send projecting fibers to the Vc, especially to terminate in the superficial Iaminae of t11e Vc. But little have been known about the neuroactive substances of those prokcting neurons. Employing a combination of Fluoro-Gold (FG) retrograde tracing with immunofluorescence bistochemical staining for neurotensin (N T) and Ieu-enkephalin (L-ENK ), we investigated the neu-rotensinergic and enkaphelinergic projections from the brainstern structures to the Vc in the rat. Neurons which send their neurotensinergic or enkephalinergic axons from brainstem to the Vc were mainly observed in the rnidbrain periaqueductal gray, nucleus raphe magnus and gigantocellular nucleus pars Q, which constitute the descending inhibitory system. The pre-sent results indicated that besides the putative transmitters of serotonin (5-HT) and substance P (SP), NT and ENK might also be the candidates of neurotransmitter and/or neuromodulators which also play irnportant roles in modulating the process of nociceptive information transmission from orofacial region. The analgesia effect of NT rnight be that NT-Iike immunoreac-tive neutons directly send their axons to the Vc, through the way of descending inhibitory system, directly rnodulate the pro-cess of nociceptive information transrnission in superficial laminae of the Vc. There were quite dense ENK-Iike immunoreac-tive terminals in the superficial laminae of the Vc, those terrninals originated not only from local region or interneurons of the Vc, but also from nuclei of descending inhibitory system and other structures of the brainstem. These wide-originated NTer-gic and ENKergic projections might inhibit and/or disinhibit the projecting neurons or interneurons in superficial laminae of the Vc, thus modulate the process of nociceptive information transrnission to the higher centers.