大鼠三叉神经尾侧亚核丘脑投射神经元与初级传入和中缝大核下行投射纤维间的突触联系

用束路追踪和免疫电镜方法研究了大鼠三叉神经尾侧亚核丘脑投射神经元与初级传入和中缝大核下行投射纤维间的突触联系。光镜观察发现，HRP跨节标记三叉神经传入终末与中缝大核（RMg）顺行追踪的PHA－L标记终末在三叉神经尾侧亚核（Vc）浅层有重叠分布。在Vc浅层丘脑投射神经元与初级传入和RMg下行投射的分布也有重叠。电镜观察发现初级传入终末和丘脑投射神经元树突形成非对称性轴树突触；而RMg下行投射终末与三叉丘脑投射神经元树突形成对称性或非对称性轴树突触，提示RMg下行投射纤维可能通过直接作用于丘脑投射神经元对初级传入的伤害性信息进行调控。

Synaptic connections between thalamic projection neurons and trigeminal primary and nucleus raphe magnus descending projection terminals in the caudal trigeminal subnucleus

Synaptic connections between thalamic projection neurons and trigeminal primary and nucleus raphe magnus descending projection terminaIs in the caudal trigeminal subnucleus were studied by using tract tracing method and immunoelectromicroscopy. Light microscopic observations show that the HRPtransganglionically labeled trigeminal primary afferent terminals and PHA-L anterogradely labeled terminals originated from nucleus raphe magnus (RMg) overlap with each other in the superficial layers of the trigeminal subnucleus caudalis (Vc). Similarly, the distributions of thalamic projection neurons, trigeminal primary afferent fibers and RMg descending projection fibers aslo overlap in the superficial layers of Vc.Elecron microscopic observations reveal that the primary trigeminal afferent terminals formed asymmetrical axodendritic synapses with thalamic projection neurons. However,the descending projection terminals originated from RMg formed both asymmetrical and symmetrical axodendritic synapses with the thalamic projection neurons. These results suggest that RMg neurons modulated primary afferent nociceptive information via direct control on thalamic projection neurons in the superficial layers of Vc.