鸡脊髓背角胶状质中calbindin-D28k阳性终末的超微结构及与substance P阳性终末之间的联系

Ultrastructure of calbindin-D28K immnoreactive neurons in laminae II of the chicken spinal dorsal horn and their relation to substance P-containing central terminals

目的观察鸡脊髓背角胶状质中calbindin-D28k(CB)阳性终末的超微结构及其与含有substance P(SP)中央末梢之间的联系。方法应用免疫电镜技术观察鸡脊髓背角胶状质中CB阳性终末的超微结构,并应用激光共聚焦显微镜观察鸡脊髓背角胶状质中CB和SP阳性突触小球中央末梢之间的关系。结果电镜下观察:1)突触小球中含有心小泡的中央末梢呈CB免疫阳性;2)突触小球内或外的部分含小泡的树突呈CB免疫阳性;以及3)突触小球外的部分轴突呈CB免疫阳性。在突触结构内,CB免疫阳性反应物主要分布于突触后膜上。免疫荧光双标记法显示,SP阳性的含有心小泡的中央末梢呈CB阳性。结论突触小球的中央末梢中CB与SP共存,提示CB可能通过其钙离子缓冲作用,参与脊髓的痛觉调制。

Objective To investigate the ultrastruacture of calbindin-D28K （CB） positive neurons in laminaelI of the chicken spinal dorsal horn, and compare them with the substance P （SP） containingcentral terminals. Methods Immunoelectron microscopy （IEM） was used to study the ultrastructure of CB-immnoreactive （IR） neurons. Laser confocal scanning microscopy was employed to study the relationships between the CB- and SP-containing elements in laminae II of the chicken spinal dorsal horn. Results CB immunoreactivity was observed in （1） the scalloped central terminal with many dense-cored vesicles （DCVs） in the synaptic glomerulus; （2） some vesicle-containing dendrites （VCDs） inside or outside the synaptic glomerulus; and （3） some axon terminals outside the synaptic glomerulus. Strong immunoreactivity was observed at the postsynaptic membrane of CB-IR elements. In double immunofluorescence, CB and SP were found to colocalize in the scalloped central terminal with DCVs of the synaptic glomerulus. Conclusion Our findings suggest that CB coexists with SP in central terminals, and CB plays an important role in the control of pain transmission through its Ca2＋-buffering action at the spinal level.