大鼠伏核内5-羟色胺样阳性终末与甲硫氨酸-脑啡肽样阳性神经元的突触联系

SYNAPTIC CONNECTIONS BETWEEN SEROTONIN LIKE IMMUNOREACTIVE TERMINALS AND METHIONINE ENKEPHALIN LIKE IMMUNOREACTIVE NEURONS IN THE NUCLEUS ACCUMBENS OF THE RAT

摘要:

本研究用免疫组织化学双重染色技术，对伏核内５羟色胺（５ＨＴ）样免疫组织化学染色阳性终末与甲硫氨酸脑啡肽（ＭｅｔＥＮＫ）样阳性神经元之间的直接突触联系进行了观察。在光镜下观察到５ＨＴ样阳性纤维和终末位于伏核吻尾向全长的各部，尤以尾段的内侧部和腹侧部较密集，但未见５ＨＴ样阳性神经元；ＭｅｔＥＮＫ样阳性神经元的胞体、纤维和终末也主要分布于伏核的内侧部和腹侧部，但数量较少。在电镜下观察到５ＨＴ样阳性终末与ＭｅｔＥＮＫ样阳性神经元的胞体和树突形成以非对称性为主的轴体和轴树突触。以上结果为来自中脑的５ＨＴ能上行纤维与伏核内ＭｅｔＥＮＫ能神经元之间以串联联系方式发挥镇痛作用提供了形态学依据。

Abstract:

The immunohistochemical double staining technique was used in the present study to investigate the synaptic connections between serotonin like immunoreactive (5 HT LI) terminals and methionine enkephalin like immunoreactive (Met ENK LI) neurons in the nucleus accumbens (Acb) of the rat. Under the light microscope, 5 HT LI fibers and terminals were located over the whole rostrocaudal extents of the Acb, but mainly in the medial and ventral regions at the caudal level of the Acb. There were no 5 HT LI neuronal cell bodies within the Acb. A few Met ENK LI neuronal cell bodies, fibers and terminals were also mainly found in the medial and ventral regions at the caudal level of the Acb. Under the electron microscope, 5 HT LI terminals were mainly observed to form asymmetrical axo dendritic synapses with the dendrites of Met ENK LI neurons. The present results provide morphological evidence that 5 HT released in the Acb by ascending serotoninergic fibers originated from midbrain might in turn activate an enkephalinergic mechanism within the Acb, which may play a role in the neural circuitry for antinociceptive effect.