Bevan M D, Bolam J P, Crossman A R
MRC Anatomical Neuropharmacology Unit, Oxford, UK.
Eur J Neurosci. 1994 Mar 1;6(3):320-34. doi: 10.1111/j.1460-9568.1994.tb00275.x.
The two major afferents of the substantia nigra pars reticulata are the subthalamic nucleus and the striatum. Stimulation of these afferents has opposing physiological effects on the output neurons of the substantia nigra pars reticulata. In order to better understand the role of these afferents in the flow of information through the basal ganglia and to better understand the ways in which they might interact, experiments have been performed to test the possibility that single-output neurons of the substantia nigra pars reticulata receive convergent synaptic input from the subthalamic nucleus and the neostriatum. To address this, rats received iontophoretic deposits of the anterograde tracer Phaseolus vulgaris leucoagglutinin in the subthalamic nucleus, injections of the anterograde tracer biocytin in the neostriatum and injections of the retrograde tracer horseradish peroxidase conjugated to wheat-germ agglutinin in the ventral medial nucleus of the thalamus. Following appropriate survival times the animals were perfusion-fixed and sections of the substantia nigra were processed to reveal the transported tracers and prepared for electron microscopy. Light microscopic examination revealed that the substantia nigra contained rich plexuses of anterogradely labelled subthalamic and striatal terminals, as well as many retrogradely labelled nigrothalamic neurons. The anterogradely labelled terminals were often seen apposed to the retrogradely labelled neurons. In the electron microscope the subthalamic terminals were seen to form asymmetrical synaptic contacts (subthalamic type 1) with the identified nigrothalamic neurons as well as unlabelled perikarya and both proximal and distal dendrites. In confirmation of previous findings, the striatal terminals made symmetrical synaptic contact with the nigrothalamic neurons as well as unlabelled neurons. In areas of overlap between the two classes of terminals, identified nigrothalamic neurons and unlabelled nigral neurons were found to receive convergent synaptic input from the subthalamic nucleus and the neostriatum. In addition to the anterogradely labelled subthalamic terminals that formed asymmetrical synaptic specializations, a second, much rarer class was also observed (subthalamic type 2). These terminals were much larger and formed symmetrical synapses; several lines of evidence suggest that they originated not in the subthalamic nucleus but in the globus pallidus. These terminals were found to make synaptic contacts with identified nigrothalamic neurons and non-labelled neurons and to form convergent synaptic contacts with subthalamic type 1 terminals and striatal terminals.(ABSTRACT TRUNCATED AT 400 WORDS)
黑质网状部的两大主要传入神经是底丘脑核和纹状体。刺激这些传入神经对黑质网状部的输出神经元具有相反的生理效应。为了更好地理解这些传入神经在通过基底神经节的信息流中的作用，以及更好地理解它们可能相互作用的方式，已开展实验来测试黑质网状部的单输出神经元是否接受来自底丘脑核和新纹状体的汇聚性突触输入这一可能性。为解决这一问题，给大鼠在底丘脑核进行了顺行示踪剂菜豆白细胞凝集素的离子电渗沉积，在新纹状体注射了顺行示踪剂生物胞素，并在丘脑腹内侧核注射了与小麦胚芽凝集素结合的逆行示踪剂辣根过氧化物酶。经过适当的存活时间后，对动物进行灌注固定，处理黑质切片以显示转运的示踪剂，并制备用于电子显微镜检查的样本。光学显微镜检查显示，黑质含有丰富的顺行标记的底丘脑和纹状体终末丛，以及许多逆行标记的黑质丘脑神经元。顺行标记的终末常常可见与逆行标记的神经元相邻。在电子显微镜下，可见底丘脑终末与已识别的黑质丘脑神经元以及未标记的胞体和近端及远端树突形成不对称突触联系（底丘脑1型）。正如先前研究结果所证实的，纹状体终末与黑质丘脑神经元以及未标记的神经元形成对称突触联系。在两类终末重叠的区域，发现已识别的黑质丘脑神经元和未标记的黑质神经元接受来自底丘脑核和新纹状体的汇聚性突触输入。除了形成不对称突触特化的顺行标记的底丘脑终末外，还观察到了第二类，且更为罕见（底丘脑2型）。这些终末要大得多，并形成对称突触；多条证据表明它们并非起源于底丘脑核，而是起源于苍白球。发现这些终末与已识别的黑质丘脑神经元和未标记的神经元形成突触联系，并与底丘脑1型终末和纹状体终末形成汇聚性突触联系。（摘要截选至400字）
