大鼠三叉神经脊束核内Ⅱ型囊泡膜谷氨酸转运体样阳性终末向外侧臂旁核的投射

Projection of vesicular glutamate transporter Ⅱ-like immunoreactive terminals from the spinal trigeminal nucleus to lateral parabrachial nucleus in rats

新近发现的Ⅰ型(VGLUT1)和Ⅱ型(VGLUT2)囊泡膜谷氨酸转运体已被作为谷氨酸能神经终末的标识物,在中枢神经系统呈互补分布,显示二者可能存在功能差异。以往的研究也已经证实接受口面部浅感觉信息的三叉神经脊束核,特别是尾侧亚核(Vc)向外侧臂旁核(LPB)发出丰富的谷氨酸能投射纤维,但该投射纤维内究竟是哪一型的囊泡膜谷氨酸转运体承担谷氨酸的转运功能,到目前为止尚未见报道。本实验选用SD大鼠,综合运用顺行束路追踪[将霍乱毒素B亚单位-CTb分别注入一侧Vc、三叉神经脊束核极间亚核(Vi)、吻侧亚核(Vo)]和免疫荧光组织化学相结合的三重标记技术,在激光共聚焦显微镜下对Vc、Vi和Vo内向LPB投射纤维内所含的囊泡膜谷氨酸转运体(VGLUTs)的情况进行了研究。结果显示:(1)将CTb分别注入大鼠一侧Vc、Vi或Vo后,在同侧的LPB内可观察到许多CTb顺行标记纤维,其中以来自Vc的标记纤维最多,Vi次之,Vo最少;(2)在LPB内可见部分CTb顺标终末同时表达VGLUT2样免疫阳性,但未见与VGLUT1样阳性终末的共存;(3)可观察到部分CTb/VGLUT2双标终末散在分布于NeuN标记的神经元的胞体周围,并与之形成密切接触。以上结果提示:大鼠口面部浅感觉、特别是伤害性信息从三叉神经脊束核向LPB传递的过程中,谷氨酸发挥着重要作用,负责其内谷氨酸转运功能的主要是VGLUT2。

The vesicular glutamate transporter 1 and 2 （ VGLUT1 and VGLUT2） was recently recognized as a marker for glutamatergic terminals and found their distribution in the central nervous system was complemental. This distributional feature may indicate their difference in function. The previous studies revealed that the spinal trigeminal nucleus, which receives superficial sensation from oro-facial region, send glutamatergle projective fibers to lateral parabmchial nucleus （LPB）, especially from caudal subnueleus of spinal trlgeminal nucleus （ Vc）. However, it has not still been reported which type of VGLUT is responsible for the transmission of glutamate in these projective fibers. The present study used SD rats and anterograde tract-tracing [ cholera toxin B subunit （CTb） injected unilaterally into the Vc, the interpolar part of spinal trigeminal nucleus （Vi） and the oral part of spinal trigeminal nucleus （Vo） ] combining with triple-immunofluores- cence histochemical technique to observe the distribution of VGLUTs in the fibers projected to the LPB from Vc, Vi and Vo under the con- focal laser-scanning microscopy. The results showed that ： （ 1 ） A large amount of the anterograde CTb-labeled fibers were observed in the ipsilateral LPB after CTb injected Vc, Vi, Vo, respectively. The projective fibers from Vc were maximum, then Vi, Vo were the least amony these CTb-labeled fibers in the LPB; （2） Some CTb-labeled terminals were expressed with VGLUT2-1ike immunoreactivity （-LI） , but no showed VGLUT1 -LI in LPB ; （ 3 ） Some of CTb/VGLUT2 double-labeled terminals were sparsely distributed the around of the NeuN-la- beled neuronal soma in the LPB and made the close contact with them. The above results indicated that the glutamate plays important role in the transmission of superficial sensation from oro-facial region, especially nocieeptive information from the spinal trigeminal nucleus to LPB in rats, and VGLUT2 is responsible for the glutamate transmission in this pathway.