GABA能神经元在大鼠、树运动皮层的分布及其电镜观察

选取进化上种风差异较大的两种动物大鼠和树　为研究材料，在光镜和电镜下观察运动皮层的GABA能神经元．两种动物运动皮层中GABA能神经元的数量、大小及所占的比例都有明显的差异．大鼠运动皮层中GABA能种经元的平均密度为140．0±49．2个／mm2，树　则为214．0±82．9个／mm2，树　的密度明显高于大鼠．大鼠从Ⅱ层到Ⅵ层GABA能神经元的数量逐层降低，而树　从Ⅱ层到Ⅴ层逐层降低，Ⅵ层的密度则高于Ⅴ层，二者密度最高的都是在Ⅱ层．大鼠GABA能神经元的最长在平均为14．2±1．2μm，树　为11．9±1．6μm．大鼠最长径在15μm以上的占29．8％；而树　仅占11．3％，树　的GABA能神经元比大鼠的要小．所以在进化较高等的动物－树　的运动皮层中，GABA能神经元的密度较高，大的GABA能神经元较少．电镜观察显示GABA能神经元表面既接受对称型突触又接受非对称型突触，两种动物非对称型突触的数目都不与GABA能神经元的周长及截面积呈线性相关．对称型突触既有GABA能的也有非GABA能的；大鼠GABA能的及非GABA能的对称型突触，和树　非GABA能的对称型突触都与GABA能神经元的周长及截面积呈线性关系．

A STUDY ON GABA-IMMUNOREACTIVE NEURONS IN THE MOTOR CORTEX OF RAT AND TREE SHREW

GABA-immunoreactive neurons in the motor cortex of rats and tree shrews we re studied with light- and electron microscopy. The densities of GABA-positive neurons were found to be 140. 0±49. 2/mm2 and 214. 0±82. 9/mm2 in the mo-tor cortex of rat and tree shrew, respectively. Tbe number of GABA-pooitive neurons decreased gradually from lamina Ⅱ to Ⅵ in the rat and from lamina Ⅱ to Ⅴ in the tree shrew, while in the later animal more GABA-positive neurons were seen in lamina Ⅵ than in lamina Ⅴ. The mean longitudinal diameters of GABAergic neurons were calculated as 14. 1±1. 2 μm in the rat and 11. 9±1. 6 μm in the tree shrew. The proportions of GABArgic neurons with longitudinal diameter > 15 μm were bigher in the rat (29. 8% ) than in the tree shrew (11. 3 % ). Therefore the phylogenetically more advanced animal, the tree shrew, has a higher density of GABAergic neurons and a lower proportion of large GABAergic neurons. It was shown under the electron microscope that both symmetrical and asymmetrical synapses were formed with GABA-positive neurons. The number of asymmetrical synapses in both animals was not related with the section areas of the neurons or their perimeters. Both GABA-positive and GABA-negative terminals wete found to establish symmetrical synapses with GABAergic neurons. In the rat, the numbers of GABA-positive and GABA-negative symmetrical synapses were linearly re-lated with the section areas (or their perimeters) of the GABArgic neurons with which the synapses were formed, whereas in the tree shrew, only those of the GABA-negative symmetrical synapses were similarly related.