大鼠脊髓背角的GABA能神经末梢来源及其突触联系──HRP追踪与免疫细胞化学结合法研究及免疫电镜观察

本文用ＨＲＰ追踪与免疫细胞化学结合法和免疫电镜技术研究了脊髓背角的ＧＡＢＡ神经元的分布、ＧＡＢＡ能末梢的来源及其超微结构联系。结果表明：在脊髓背角Ⅰ～Ⅵ层内均有ＧＡＢＡ神经元胞体和纤维分布，其中Ⅰ～Ⅲ层较为密集，在后外侧束内也存在ＧＡＢＡ能纤维及胞体。脊髓背角的ＧＡＢＡ能神经末梢有３个来源：①延髓的大缝核、隐缝核、苍白缝核及腹侧网状结构的ＧＡＢＡ能神经元；②脊髓固有的ＧＡＢＡ能神经元；③脊神经节的ＧＡＢＡ能神经元。ＧＡＢＡ能末梢可作为突触前成分或突触后成分与未标记末梢形成轴－树突触，也可同时作为突触前、后成分而形成轴－树型自调节突触。结果提示突触前的ＧＡＢＡ能末梢可能对脊髓背角内的其它神经元起抑制和脱抑制作用；同时背角内ＧＡＢＡ能神经元还接受其它神经元的调控。

ORIGINS AND SYNAPTIC CONNECTIONS OF GABAERGIC FIBERS IN THE SPINAL DORSAL HORN OF THE RAT──A STUDY WITH A COMBINED METHOD OF HRP TRACING AND IMMUNOCYTOCHEMISTRY AND AN IMMUNOELECTRON MICROSCOPIC OBSERVATION

The GABAergic neurons and the origins and synaptic connections of the GABAergic fibers in the spinal dorsal horn of the rat were studied by a combined method of HRP retrograde tracing and immunocytochemistry as well as an immunoelectron microscopic technique. The results showed that there were GABA positive somata and fibers in laminae Ⅰ～Ⅵ of the cervical spinal dorsal horn- A higher density of GABA positive somata and terminals was distributed in laminae Ⅰ～Ⅲ . GABA-positive somata and fibers were also visible in Lissauer's tract. There were three sources of GABAergic terminals in the cervical spinal dorsal horn: ( 1 ) GABA neurons of nucleus raphe magus ,nucleus raphe obscurus ,nucleus raphe pallidus and the ventral part of the reticular formation of medulla oblongata; (2) Intrinsic GABA neurons of the spinal cord; (3) GABA neurons of the dorsal root ganglia. GABAergic terminals might serve as presynaptic elements or postsynaptic elements to form axo-dendritic synapses with GABA-negative terminals. In addition,GABAergic terminals might serve simultaneously as presynaptic and postsynatic elements to make autoregulatory synapses.The results indicated that presynaptic GABAergic terminals might inhibit or disinhibit other neurons in the spinal dorsal horn;and the GABA neurons of the spinal dorsal horn themselves might be controlled or regulated by neurons containing other neurotransmitters.