VGluT1样阳性终末在大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”内的分布及来源

本文综合运用免疫组织化学、逆行束路追踪和免疫荧光组织化学双标技术,对Ⅰ型囊泡膜谷氨酸转运体(VGluT1)样阳性终末在大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”内的分布和来源、以及与向丘脑腹后内侧核(VPM)投射的神经元之间的联系进行了研究。结果显示:(1)在组成“带状区”的四个核团,即三叉神经感觉主核背内侧部(Vpdm)、三叉上核尾外侧部(Vsup-CL)、三叉神经运动核腹侧区(AVM)和上橄榄核背侧区(ADO)内,均可观察到大量的VGluT1样阳性终末呈密集分布;(2)将逆行追踪剂四甲基罗达明(TMR-DA)注入丘脑VPM后,在上述核团内均可观察到大量的TMR逆标神经元的胞体和突起;(3)在激光共聚焦显微镜下可观察到部分VGluT1样阳性终末包绕在TMR逆标神经元的胞体或树突周围,并与之形成密切接触;(4)当切断三叉神经感觉根7d后,光学显微镜下可观察到手术侧Vpdm内的VGluT1样阳性产物明显下降,其他三个核团内无明显变化,但当切断三叉神经运动根8周后,则在手术侧Vsup内观察到VGluT1样阳性产物几乎完全消失,而Vpdm、AVM和ADO内并无变化。以上结果提示:(1)大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”的四个核团内均有大量的VGluT1样阳性终末分布,但它们的来源有所不同,其中Vpdm内的VGluT1样阳性终末来自于外周的三叉神经节细胞,Vsup内的VGluT1样阳性终末来自于三叉神经中脑核神经元,而AVM和ADO内的VGluT1样阳性终末可能来自于中枢其他核团;(2)口面部本体感觉信息从“带状区”向丘脑VPM传递的过程中,谷氨酸发挥着重要作用。

DISTRIBUTION AND ORIGIN OF VGLUT1-POSITIVE TERMINALS ON THIRD-ORDER NEURONS-"ZONE-SHAPED AREA" ON THE CENTRAL PATHWAY OF THE TRIGEMINAL PROPRIOCEPTIVE SENSATION IN THE RAT

In the present study, immunohistochemistry and retrograde-tract tracing combined immunofluorescence histochemical techniques were used to observe the distribution and the origin of vesicular glutamate transporter 1-like immunoreactive (VGluT1-LI) terminals in the third-order neurons-“zone-shaped area” on the central pathway of the trigeminal proprioceptive sensation in the rat, and connections between the VGluT1-LI terminals and the neurons projection into the ventral posteromedial nucleus (VPM) of the thalamus. The results showed: (1)Large amounts of VGluT1-LI terminals were intensively distributed in the whole “zone-shaped area” which is made up of the dorsomedial part of the principal sensory trigeminal nucleus (Vpdm), the caudolateral part of the supratrigeminal nucleus (Vsup-CL), the area ventral to motor trigeminal nucleus (AVM) and the area dorsal to the superior olivery nucleus (ADO) of the rat; (2)After injection tetramethylrhodamine-dextran amine(TMR-DA)into the VPM of the thalamus, many of retrograde TMR-labeled neuronal cell bodies and processes were mainly observed in the whole “zone-shaped area”; (3)Confocal laser-scanning microscopy revealed that axonal varicosities with some of VGluT1-LI terminal surrounded the somata and dendrites of TMR-labeled neurons, and formed the close contact with them; (4)After 7 days unilateral transection of the sensory root of trigeminal nerve, the decrease of VGluT1-like immunoreactivity on the operation side was much more evident in the Vpdm, but no changes were found in the other three nuclei. On the other hand, after 8 weeks unilateral transection of the motor root of trigeminal nerve, VGluT1-like immunoreactivity on the operation side was detected to almost all disappeared in the Vsup, but no changes were observed in the Vpdm, AVM and ADO. The above results suggest that: (1) A considerable number of VGluT1-LI terminals were widely distributed in the third-order neurons-“zone-shaped area” on the central pathway of the trigeminal proprioceptive sensation in the rat, but they had the different origins. Those VGluT1-LI terminals in the Vpdm and the Vsup originated from the trigeminal ganglion neurons and the mesencephalic trigeminal nucleus, respectively, while those VGluT1-LI terminals in the AVM and ADO maybe originated the central other origins; (2)Glutamate plays important role in the transmission of the orofacial regional proprioceptive sensory signals from the “zone-shaped area” to the VPM of the thalamus.