Karle E J, Anderson K D, Reiner A
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163.
Brain Res. 1992 Feb 14;572(1-2):303-9. doi: 10.1016/0006-8993(92)90490-z.
Immunohistochemical studies in rats have demonstrated dopaminergic input onto medium spiny neurons of the striatum. Medium spiny neurons, however, are known to consist of two major neuropeptide-specific types, those containing substance P (SP) and those containing enkephalin. Although both of these types have been shown to receive dopaminergic input onto their perikarya and proximal dendrites, the extent to which both types also receive direct dopaminergic input onto distal dendritic shafts or onto dendritic spines is uncertain. In the present study, we used EM immunohistochemical double-label techniques to examine the synaptic organization of dopaminergic input onto SP+ striatal neurons. We examined the striatum of pigeons, in whom SP+ striatal neurons, including their dendritic shafts and spines, can be readily labeled. Antibodies against tyrosine hydroxylase (TH) were used to identify dopaminergic terminals, which were labeled using silver-intensified immunogold. The SP+ neurons were labeled immunohistochemically using diaminobenzidine. We found that dopaminergic terminals make appositions and form symmetric synapses with the perikarya, dendritic shafts and dendritic spines of SP+ neurons. Thus, nigral dopaminergic neurons provide a monosynaptic input onto SP+ striatal neurons in a manner similar to that described for dopaminergic input onto striatal medium spiny neurons in general.
对大鼠的免疫组织化学研究已证实，多巴胺能神经纤维投射至纹状体的中等棘状神经元。然而，已知中等棘状神经元主要由两种主要的神经肽特异性类型组成，即含P物质（SP）的神经元和含脑啡肽的神经元。尽管已表明这两种类型的神经元在其胞体和近端树突上均接受多巴胺能神经纤维投射，但这两种类型的神经元在远端树突干或树突棘上是否也接受直接的多巴胺能神经纤维投射尚不确定。在本研究中，我们使用电子显微镜免疫组织化学双重标记技术，来检查多巴胺能神经纤维投射至SP⁺纹状体神经元的突触组织。我们研究了鸽子的纹状体，在鸽子中，包括其树突干和树突棘在内的SP⁺纹状体神经元很容易被标记。使用抗酪氨酸羟化酶（TH）抗体来识别多巴胺能终末，这些终末用银增强免疫金标记。SP⁺神经元用二氨基联苯胺进行免疫组织化学标记。我们发现，多巴胺能终末与SP⁺神经元的胞体、树突干和树突棘形成并置连接并形成对称突触。因此，黑质多巴胺能神经元以类似于一般所描述的多巴胺能神经纤维投射至纹状体中等棘状神经元的方式，为SP⁺纹状体神经元提供单突触输入。
