Carlton S M, Westlund K N, Zhang D, Willis W D
Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555.
J Comp Neurol. 1992 Aug 22;322(4):528-37. doi: 10.1002/cne.903220407.
Gamma-aminobutyric acid (GABA) is a putative inhibitory neurotransmitter in the vertebrate nervous system. Several lines of evidence suggest that GABA plays an important role in the processing and modulation of sensory input in the spinal cord dorsal horn. In the present study, the relationship between GABA-immunoreactive (GABA-IR) terminals and spinothalamic tract (STT) cells in the monkey lumbar cord was investigated. Physiologically characterized STT cells, one located in lamina V and two located in lateral lamina IV, were intracellularly injected with horseradish peroxidase (HRP). A fourth STT cell, located in lamina I, was retrogradely labeled following injection of HRP into the contralateral thalamus. Immunogold labeling of ultrathin sections through the cell bodies and proximal dendrites of the STT neurons demonstrated that the percentage of the GABA-IR terminals in contact with these profiles was 24.7% and 36%, respectively. The average STT surface length contacted by GABA-IR terminals for cell bodies and proximal dendrites was 18.2% and 26.7%, respectively. For the lamina I cell, 7 out of 35 (20%) of the terminals were GABA-IR and they covered 9.6% of the surface analyzed. These data demonstrate that GABA-IR terminals synapse directly on STT cells, constituting a substantial proportion of the terminal population on these cells. Furthermore, compared to the cell bodies, a greater percentage of the input on the proximal dendrites is GABAergic. These anatomical data are consistent with the findings of a previously published iontophoretic study that demonstrated that GABA can exert a strong inhibitory influence on STT cells. These findings are discussed in relation to GABAergic involvement in tonic and phasic inhibition of STT neurons.
γ-氨基丁酸（GABA）被认为是脊椎动物神经系统中的一种抑制性神经递质。多项证据表明，GABA在脊髓背角感觉输入的处理和调节中发挥着重要作用。在本研究中，研究了猴腰髓中GABA免疫反应性（GABA-IR）终末与脊髓丘脑束（STT）细胞之间的关系。对生理特性明确的STT细胞（1个位于V层，2个位于外侧IV层）进行辣根过氧化物酶（HRP）细胞内注射。将HRP注入对侧丘脑后，对位于I层的第4个STT细胞进行逆行标记。通过STT神经元的胞体和近端树突的超薄切片的免疫金标记显示，与这些结构接触的GABA-IR终末的百分比分别为24.7%和36%。GABA-IR终末与胞体和近端树突接触的STT平均表面长度分别为18.2%和26.7%。对于I层的细胞，35个终末中有7个（20%）是GABA-IR，它们覆盖了所分析表面的9.6%。这些数据表明，GABA-IR终末直接与STT细胞形成突触，在这些细胞的终末群体中占相当大的比例。此外，与胞体相比，近端树突上的输入中GABA能的比例更高。这些解剖学数据与先前发表的离子电泳研究结果一致，该研究表明GABA可对STT细胞施加强烈的抑制作用。结合GABA能参与STT神经元的紧张性和相位性抑制对这些发现进行了讨论。
