大鼠中缝大核内M—ENK样树突和轴突终末的超微结构

ULTRASTRUCTURE OF MET-ENKEPHALIN(ENK)DENDRITES AND AXON TERMINALS IN THE NUCLEUS RAPHE MAGNUS OF THE RAT

本文用免疫细胞化学PAP 法,在电镜下观察中缝大核(NRM)内甲硫脑啡肽(M—ENK)样免疫反应树突和轴突终末的形态和突触关系。M—ENK 样免疫反应树突数量较多,直径粗细不等,接受一个或多个突触传入;根据标记情况,可分为浓染型和淡染型两种。M—ENK 样轴突包括有髓纤维和无髓纤维两类。M—ENK 样轴突终末含有清亮圆囊泡或相伴颗粒囊泡。所见突触型式有:(1)轴—树(M—ENK)突触,(2)轴—棘(M—ENK)突触,(3)轴—轴(M—ENK)突触,(4)轴(M—ENK)—树突触。上述结果提示NRM 内脑啡呔能缝—脊神经元接受多种信息传入,可能具有整合作用;脑啡肽能轴突终末参与核团内局部突触调节,并存在突触前调节机制。

The method of electron immunocytochemistry was used to identify the ultrastructure fo met-enkephalin (ENK) dendrites and axon terminals and their synaptie relations with other neural elements in the nucleus raphe magnus (NRM) of the rat.Numerous immunoreactive ENK-labelled small,medium-sized and large dendrites were distributed in the neuropil of theNRM.Two classses of ENK dendrites were distinguished in the nucleus.The first was rich in mitochondria,endoplasmic retieulum,vesicles,microtubules and often heavy-labelled.The second only containes microtubules.ENK dendrites were contacted by single or several unlabelled axon terminals.Both unmyelinated and myel nated ENK fibers were found in the NRM. ENK-labelled axon terminals or varicosities contained clear round vesicles and large granular vesicles(80-100 μm),but ENK-labelled presynaptic boutons contained clear round vesicles.ENK-labelled dendrites and axon terminals were involved in several synaptic interactions:(a)axo-dendritic(ENK)synapses,(b)axo-dendritie spine (ENK) synapses,the unlabelled presynaptie boutons containing clear round vesicles or mixed with small or large granular vesicles,(c)axo-axonic(ENK)synapses, and(d)axo(ENK)-dendritic synapses.These results suggest that several neuronal systems with possible different transmitters may regulate ENKergic raphe-spinal neurons.The ENK axon terminals participate in local synaptic regulation within the NRM.