三叉神经脊束核尾侧亚核P物质轴突终末的大颗粒小泡分布特点和突触联系

THE DISTRIBUTION OF LARGE GRANULAR VESICLES IN SUBSTANCE P AXON TERMINALS AND THEIR SYNAPTIC RELATIONS IN THE TRIGEMINAL SUBNUCLEUS CAUDALIS

本文用免疫电镜方法,研究了大鼠三叉神经脊束核尾侧亚核P物质(SP)的超微结构定位,重点为SP轴突终末内阳性大颗粒小泡(LGV)的形态、数目及分布特点。结果表明,SP免疫反应产物位于轴突终末和细无髓轴突内。SP轴突终末免疫反应产物主要位于LGV内、清亮小泡表面及线粒体外膜。LGV呈圆形、椭圆形,直径60～120nm,一个终末内一般含有2～3个,多者可达20个,它们分布于终末内的中央或周边,在形成突触的SP轴突终末,LGV远离突触活性区。切除一侧刚髭部皮肤,损伤侧三叉神经脊束核尾侧亚核SP轴突终末内,LGV多沿周边分布,尤以14天最多。沿周边的LGV有的与轴膜接触或融合。计数了1302个SP轴突终末有11.67％形成突触,几乎全部与未标记的树突形成轴-树突触,仅见1例轴-轴突触。本文并对SP阳性LGV在轴突终末的分布特点及其机能意义进行了探讨。

The ultrastructural localization of substance P (SP) immunoreactivity, especially the morphology, number and distribution of positive large granular vesicles (LGV) in SP axon terminals of the trigeminal subnucleus caudalis of the rat were studied by electron microscopic immunocytochemistry. This study revealed that SP immunoreactivity was mostly located in axon terminals and unmyelinated fibers. SP axon terminals contained both clear round vesicles and LGV. SP immunoreactivity was found in LGV, and on the surface of clear round vesicles and outer membrane of mitochondria. Positive LGV were spherical or oval in shape (60～120nm in diameter). The number of LGv was mostly 2～3 in a SP axon terminal. LGV often apposed to the axolemma or scattered in the centre of terminal. LGV were far from the presynaptic sites of the SP terminals which formed synapses. The number of LGV closed to the terminal membrane was significantly (P<0.001) increased on the ipsilateral side in the trigeminal subnucleus caudalis 1 hour and 14 days (especially 14 days) after unilateral skin excision in the vibrissae area. Some LGV seemed to be attached to the terminal membrane to formed contact and fusion. Totally 1302 SP axon terminals were observed in the trigeminal subnucleus caudalis, 11.67% of axon terminals formed synaptic relations. Nearly all of the SP terminals formed axodendritic synapses with unlabelled dendrites except that one axo-axonic synapse was formed. The significance of LGV in SP terminals was discussed.