De Biasi S, Vitellaro-Zuccarello L, Bernardi P, Valtschanoff J G, Weinberg R J
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
J Comp Neurol. 1994 Sep 8;347(2):275-87. doi: 10.1002/cne.903470209.
The cuneate nucleus is a relay center for somatosensory information by receiving tactile and proprioceptive inputs from primary afferent fibers that ascend in the dorsal funiculus. The morphology, synaptic contacts, and neurochemical content of primary afferent terminals in the cuneate nucleus of rats were investigated by combining anterograde transport of horseradish peroxidase conjugated to wheat-germ agglutinin or to cholera toxin (injected in cervical dorsal root ganglia) with postembedding immunogold labeling for glutamate and GABA. Both tracers gave similar results. Two types of terminals were labeled: type I terminals were irregularly shaped, had a mean area of 4.0 microns 2, synapsed on several dendrites, and were contacted by other terminals, some of which were GABA positive. Type II terminals were dome-shaped, had a mean area of 2.18 microns 2, and made synaptic contact on a single dendrite. All the anterogradely labeled terminals (interpreted as endings of primary afferents) were enriched in glutamate but not in GABA. The finding that identified primary afferent terminals are enriched in glutamate with respect to other tissue profiles strongly suggests a neurotransmitter role for glutamate in this afferent pathway to the rat cuneate nucleus.
楔束核是躯体感觉信息的中继中心，它通过接收来自在背索中上行的初级传入纤维的触觉和本体感觉输入。通过将与小麦胚芽凝集素或霍乱毒素结合的辣根过氧化物酶（注射到颈背根神经节）的顺行运输与谷氨酸和GABA的包埋后免疫金标记相结合，研究了大鼠楔束核中初级传入终末的形态、突触联系和神经化学含量。两种示踪剂给出了相似的结果。标记了两种类型的终末：I型终末形状不规则，平均面积为4.0平方微米，与多个树突形成突触，并与其他终末接触，其中一些是GABA阳性的。II型终末呈穹顶状，平均面积为2.18平方微米，与单个树突形成突触联系。所有顺行标记的终末（被解释为初级传入的终末）富含谷氨酸而非GABA。与其他组织成分相比，已确定的初级传入终末富含谷氨酸这一发现强烈表明谷氨酸在这条通向大鼠楔束核的传入通路中起神经递质作用。
