大鼠延髓孤束核吻侧段内脑啡肽免疫阳性轴突末梢与含阿片μ受体的γ-氨基丁酸能神经元之间的突触联系

Synapses between ENK immunoreactive terminals and GABAergic neurons bearing μ opioid receptor in the rostral portion of nucleus tractus solitarious in rat

目的:观察大鼠孤束核吻侧段(rNTS)内脑啡肽免疫反应阳性(ENK-ir)终末、γ-氨基丁酸免疫反应阳性(GA-BA-ir)神经元及阿片μ受体免疫反应阳性(MOR-ir)神经元三者之间的联系。方法:包埋前免疫组织化学方法显色结合免疫金颗粒双重标记后,电镜观察。结果:在电镜下可见ENK-ir产物主要定位于圆形清亮突触小泡及大颗粒囊泡表面,GABA-ir产物主要分布于胞体及树突内部,多见于粗面内质网及核糖体等结构,MOR-ir产物主要位于树突膜、线粒体膜、内质网膜等结构表面;ENK-ir轴突终末与GABA-ir神经元胞体及树突之间形成对称性和非对称性的突触联系,以对称性突触为主;ENK-ir轴突终末与MOR-ir神经元的胞体及树突形成以对称性突触为主的突触联系;GA-BA-ir与MOR-ir产物共存于神经元内,GABA/MOR-ir神经元与免疫反应阴性的终末形成对称性和非对称性突触,以对称性突触为主。结论:rNTS内的ENK-ir终末可能通过与MOR结合,调节GABA能神经元的活性,从而参与味觉信息的感受和调节。

Objective： To observe the connections among enkephalin immunoreactive （ENK-ir）terminals, γ-aminobutyric acid immunoreactive （GABA-ir） neurons and μ opioid receptor （MOR） immunoreactive （MOR-ir）neurons in the rostral portion of the nucleus tractus solitarious （rNTS） in rats. Methods： Preembedding immunohistochemical staining combined with immunogold labeling technique for electron microscopy were used in the present study. Results： Under electron microscope, ENK-ir reaction products were mainly localized on the surface of round clear vesicles and dense -cored vesicles in the axon terminals. GABA-ir reaction products were mainly localized on the rough endoplasmic reticulum and ribosome in cell bodies and dendrites. MOR-ir reaction products were mainly localized on the membrane of dendrites and mitochondria; ENK-ir terminals formed symmetric （mainly） and asymmetric synaptic connections with GABA-ir cell bodies and dendrites; ENK-ir terminals formed symmetric synaptic connection （mainly） with MOR-ir cell bodies and dendrites; GABA/MOR coexisted in neurons were observed in the rNTS, and GABA and MOR coexisted in neurons formed symmetric synaptic（mainly） and asymmetric synaptic connections with the immunonegative terminals. Conclusion： These results indicate that ENK might have regulatory effects on GABAergic neurons in rNTS by bonding with MOR, and take part in the transmission and regulation of the taste information.