大鼠三叉神经本体觉中枢通路二级神经元中继咬肌本体觉传入的微超结构证据

将Ricin注入大鼠咬肌神经,存活2周左右,再将HRP分别定位电泳于作为三叉神经本体觉中枢通路三级传入神经元所在地的三叉神经感觉主核背内侧部(Vpdm)和三叉神经运动核腹侧区(AVM)。电镜观察结果表明,在三叉神经本体觉中枢通路二级传入神经元所在地的三叉神经脊束核吻侧亚核背内侧部(Vodm),初级传入的溃变终末与HRP逆标的树突间形成非对称型突触,确证了Vodm是三叉神经本体觉中枢通路的中继核团。突触后树突多为中间树突和近侧树突。此外,在Vodm区还发现来自Vpdm的顺行标记终末与非标记的树突形成突触。本研究证明Vodm区超微结构有以下几个特征:(1)轴-体突触极少见;(2)轴-棘突触少见;(3)突触小球结构少见;(4)大扇贝形终末较少见;(5)这一区域也有小颗粒泡和大颗粒泡终末。这些超微结构特征,可能是Vodm与三叉神经感觉核簇其它部位区别之点,也可能是本体感觉中继核团特有的结构特征。

ULTRASTRUCTURAL EVIDENCE FOR A TRIGEMINAL PROPRIOCEPTIVE PATHWAY: ITS SECOND-ORDER NEURONS RELAY THE MASTICA- TORY PROPRIOCEPTIVE AFFERENTS TO THE THIRD-ORDER NEURONS OF THE PATHWAY

Ricinus communis (RCA60, Sigma) was injected into the masseter nerve of rats, and after about 2 weeks of survival, HRP was introduced into either dorsomedial part of the principal sensory trigeminal nucleus (Vpdm) or the area ventral to the motor trigminal nucleus (AVM) by electrophoresis. In both the Vpdm and AVM HRP injection cases, it could be seen that electron dense degenerated terminals contacted or synapsed on the HRP labeled dendrites. The type of synapses could be identified in some moderately degenerated terminals: they were mostly asymmetrical synapses with clear spherical vesicles. The degenerated endings generally terminated on the shafts of primary and medium-sized dendrites. Besides degenerated endings, HRP labeled terminals were observed to synapse on the unlabeled dendrites in dorsomedial part of the subnucleus oralis (Vodm), indicating feed-back projections from the Vpdm or AVM to the Vodm. Thus, the above pathway has been established atthe ultrastructural level.Ultrastructural characteristics of the Vodm was also demonstrated: A. few of axo-somatic synapses; B. lack of axo-spinal synapses; C. rarely-seen synaptic glomeruli; D. occasionally-seen large scallopshape terminals; E. buttons with large or small granular vesicles could be observed in this region.