Meredith G E, Wouterlood F G
Department of Anatomy and Embryology, Faculty of Medicine, Free University, Amsterdam, The Netherlands.
J Comp Neurol. 1990 Jun 8;296(2):204-21. doi: 10.1002/cne.902960203.
The synaptic interactions between terminals of allocorticostriatal and thalamostriatal fibers and the cholinergic neurons in the nucleus accumbens were investigated using degeneration and dual labelling immunocytochemistry in Wistar rats. The presumptive cholinergic neurons were labelled with antibodies directed against choline acetyltransferase and the afferent fibers were labelled anterogradely with Phaseolus vulgaris-leucoagglutinin. Fibers from the subiculum of the hippocampal formation and from the midline and intralaminar thalamus project densely into the medial nucleus accumbens where they overlap a relatively dense population of choline acetyltransferase-immunoreactive neurons. Varicosities containing Phaseolus vulgaris-leucoagglutinin juxtapose the immunoreactive neurons. To study the possibility that the cholinergic neurons could be the synaptic targets of these incoming fibers, the subiculum, the fornix, and the midline/intralaminar thalamus were lesioned in separate animals and brain sections were immunoprocessed for choline acetyltransferase and studied with the electron microscope. In addition, dual-labelling electron microscopic immunocytochemistry was employed. In total, 164 synaptic terminals from the subiculum/hippocampus and 130 from the midline/intralaminar thalamus were examined; all formed asymmetrical synaptic specializations. No hippocampal endings were seen to contact the somata or primary dendrites of the choline acetyltransferase-immunoreactive neurons; however, three were found in synaptic contact with distal, immunolabelled dendritic shafts. Most hippocampal terminals established contacts with unlabelled spines. Fifteen percent of the thalamic endings were found to synapse on the somata and the primary and distal dendrites of the choline acetyltransferase-immunoreactive neurons. The remaining thalamic terminals established synaptic junctions with small unlabelled dendrites or spines. These findings have important implications not only for our understanding of the synaptic organization of the hippocampal and thalamic projections to the nucleus accumbens, but also for the contribution of the cholinergic neurons to the circuitry of this nucleus.
运用变性和双重标记免疫细胞化学方法，在Wistar大鼠中研究了异皮质纹状体和丘脑纹状体纤维终末与伏隔核内胆碱能神经元之间的突触相互作用。用抗胆碱乙酰转移酶抗体标记假定的胆碱能神经元，并用菜豆白细胞凝集素对传入纤维进行顺行标记。来自海马结构下托以及中线和板内核的纤维密集投射到伏隔核内侧，在那里它们与相对密集的胆碱乙酰转移酶免疫反应性神经元群体重叠。含有菜豆白细胞凝集素的膨体与免疫反应性神经元并列。为了研究胆碱能神经元可能是这些传入纤维的突触靶点，在不同动物中损毁下托、穹窿和中线/板内核，并对脑切片进行胆碱乙酰转移酶免疫处理，然后用电子显微镜进行研究。此外，还采用了双重标记电子显微镜免疫细胞化学方法。总共检查了来自下托/海马的164个突触终末和来自中线/板内核的130个突触终末；所有这些终末都形成了不对称的突触特化结构。未观察到海马终末与胆碱乙酰转移酶免疫反应性神经元的胞体或初级树突接触；然而，发现有3个与免疫标记的远端树突干形成突触联系。大多数海马终末与未标记的棘形成联系。发现15%的丘脑终末与胆碱乙酰转移酶免疫反应性神经元的胞体、初级和远端树突形成突触。其余的丘脑终末与未标记的小树突或棘形成突触连接。这些发现不仅对我们理解海马和丘脑向伏隔核投射的突触组织具有重要意义，而且对胆碱能神经元在该核神经回路中的作用也具有重要意义。
