Medina L, Anderson K D, Karle E J, Reiner A
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163, USA.
J Comp Neurol. 1995 Jul 3;357(3):408-32. doi: 10.1002/cne.903570307.
Electron microscopic immunohistochemical double-label studies were carried out in pigeons to characterize the ultrastructural organization and postsynaptic targets of enkephalinergic (ENK+) striatonigral projection. ENK+ terminals in the substantia nigra were labeled with antileucine-enkephalin antiserum by using peroxidase-antiperoxidase methods, and dopaminergic neurons were labeled with anti-tyrosine hydroxylase antiserum by using silver-intensified immunogold methods. ENK+ terminals on dopaminergic neurons were equal in abundance to ENK+ terminals on nondopaminergic neurons, although the former were typically somewhat smaller than the latter (mean size: 0.50 vs. 0.75 micron, respectively). ENK+ terminals were evenly distributed on the cell bodies and dendrites of dopaminergic neurons, and they were evenly distributed on dendrites but rare on perikarya of nondopaminergic neurons. Transection of the basal telencephalic output revealed that 75% of the nigral ENK+ terminals were of basal telencephalic origin. These telencephalic ENK+ terminals included over 80% of those smaller than 0.80 micron on dopaminergic neurons and smaller than 1.0 micron on nondopaminergic neurons, and none greater than this in size. Both telencephalic and the nontelencephalic ENK+ nigral terminals made predominantly symmetric synapses on nigral neurons. Although the basal telencephalic ENK+ terminals uniformly targeted dendrites and perikarya, nontelencephalic ENK+ terminals seemed to avoid perikarya. The results indicate that ENK+ striatonigral neurons in birds may directly influence both dopaminergic and nondopaminergic neurons of the substantia nigra. Based on similar data for substance P-containing striatonigral terminals, the roles of enkephalin and substance P in influencing nigral dopaminergic neurons may differ slightly, as they appear to target preferentially different portions of dopaminergic neurons. The overall results in pigeons are similar to those for ENK+ terminals in the ventral tegmental area in rats, suggesting that the synaptic organization of the ENK+ input to the tegmental dopaminergic cell fields is similar in mammals and birds.
为了描述脑啡肽能（ENK+）纹状体黑质投射的超微结构组织和突触后靶点，对鸽子进行了电子显微镜免疫组织化学双标记研究。采用过氧化物酶-抗过氧化物酶方法，用抗亮氨酸脑啡肽抗血清标记黑质中的ENK+终末，采用银增强免疫金方法，用抗酪氨酸羟化酶抗血清标记多巴胺能神经元。多巴胺能神经元上的ENK+终末数量与非多巴胺能神经元上的ENK+终末数量相当，尽管前者通常比后者略小（平均大小分别为0.50微米和0.75微米）。ENK+终末均匀分布在多巴胺能神经元的胞体和树突上，它们均匀分布在非多巴胺能神经元的树突上，但在其胞体上很少见。切断基底端脑输出显示，75%的黑质ENK+终末起源于基底端脑。这些端脑ENK+终末包括多巴胺能神经元上小于0.80微米和非多巴胺能神经元上小于1.0微米的终末中的80%以上，且大小均不超过此值。端脑和非端脑的ENK+黑质终末在黑质神经元上主要形成对称性突触。尽管基底端脑的ENK+终末均匀地靶向树突和胞体，但非端脑的ENK+终末似乎避开胞体。结果表明，鸟类中的ENK+纹状体黑质神经元可能直接影响黑质中的多巴胺能和非多巴胺能神经元。基于含P物质的纹状体黑质终末的类似数据，脑啡肽和P物质在影响黑质多巴胺能神经元方面的作用可能略有不同，因为它们似乎优先靶向多巴胺能神经元的不同部分。鸽子的总体结果与大鼠腹侧被盖区ENK+终末的结果相似，表明哺乳动物和鸟类中ENK+输入到被盖多巴胺能细胞区的突触组织相似。
