Clarke N P, Bolam J P, Bevan M D
MRC Anatomical Neuropharmacology Unit and Department of Pharmacology, Mansfield Road, Oxford OX1 3TH, UK.
Eur J Neurosci. 1996 Jul;8(7):1363-76. doi: 10.1111/j.1460-9568.1996.tb01599.x.
In order to clarify the origin and to examine the synaptology of the projection from the mesopontine tegmentum to the entopeduncular nucleus, rats received discrete deposits of anterograde tracers in different regions of the mesopontine tegmentum. Anterogradely labelled fibres in the entopeduncular nucleus were analysed at the light and electron microscopic levels. To determine the neurochemistry of the projection, the distributions of GABA and glutamate immunoreactivity in anterogradely labelled boutons in the entopenducular nucleus were studied by postembedding immunocytochemistry. The morphological characteristics of anterogradely labelled structures were compared to those of choline acetyltransferase-immunopositive structures. The anterograde tracing demonstrated that the projection to the entopeduncular nucleus arises from the area defined by the cholinergic neurons of the pedunculopontine region and from the more medial and largely non-cholinergic, midbrain extrapyramidal area. The anterogradely labelled terminals formed asymmetrical synaptic contacts with dendritic shafts, cell bodies and more rarely spines in the entopeduncular nucleus, and they were significantly enriched in glutamate immunoreactivity compared to identified GABAergic terminals in the same region. The morphology, trajectory and synaptology of the anterogradely labelled fibres showed similarities to those of choline acetyltransferase-immunopositive fibres and terminals, providing indirect evidence in support of previous suggestions that at least part of the projection is cholinergic. The structures postsynaptic to the anterogradely labelled boutons also received input from other classes of terminals that had the morphological and neurochemical characteristics of boutons derived from the neostriatum, globus pallidus and subthalamic nucleus. These findings imply that the mesopontine tegmentum sends a projection to the entopeduncular nucleus that is heterogeneous with respect to its origin and also possibly its neurochemistry. The synaptology of the projection underlies one route through which the mesopontine tegmentum can exert effects on movement by modulating the direct and indirect pathways of information flow through the basal ganglia.
为了阐明中脑桥被盖向脚内核投射的起源并研究其突触学，给大鼠在中脑桥被盖的不同区域离散注入顺行示踪剂。在光镜和电镜水平分析脚内核中顺行标记的纤维。为了确定投射的神经化学性质，通过包埋后免疫细胞化学研究了脚内核中顺行标记终扣内GABA和谷氨酸免疫反应性的分布。将顺行标记结构的形态特征与胆碱乙酰转移酶免疫阳性结构的形态特征进行比较。顺行追踪显示，向脚内核的投射起源于脚桥核胆碱能神经元所界定的区域以及更内侧且大部分为非胆碱能的中脑锥体外区域。顺行标记的终末在脚内核中与树突干、胞体形成不对称突触联系，与棘形成突触联系的情况较少见，并且与同一区域已确定的GABA能终末相比，它们的谷氨酸免疫反应性显著增强。顺行标记纤维的形态、走行和突触学与胆碱乙酰转移酶免疫阳性纤维和终末相似，为先前关于至少部分投射是胆碱能的观点提供了间接证据。顺行标记终扣的突触后结构也接受来自其他类型终末的输入，这些终末具有源自新纹状体、苍白球和底丘脑核的终扣的形态和神经化学特征。这些发现表明，中脑桥被盖向脚内核发出的投射在起源以及可能还有神经化学性质方面是异质性的。该投射的突触学构成了中脑桥被盖通过调节基底神经节信息流的直接和间接途径对运动产生影响的一条途径。
