士的宁局部刺激与氯化钾扩散阻抑时大脑皮质核糖核酸含量和酸性磷酸酶活性的变化

THE HISTOCHEMICAL CHANGES OF THE CEREBRAL CORTEX DURING STRYCHNIZATION AND SPREADING DEPRESSION CAUSED BY LOCAL APPLICATION OF POTASSINM CHLORIDE

Dusser de Barrenne 发现,以士的宁涂抹在大脑皮质表面,能引起局部神经元的同步节律放电,出现“士的宁峯电位”(Strychnine Spikes);并由此创立了“士的宁神经元绘图法”(Strychnine neuronography)以追寻神经元之间的连系。目前关于士的宁对大脑神经元作用的生理学机制,已有不少研究。张香桐的工作指出:在2%士的宁涂在大脑表面,能增高皮质诱发电位的刺激阈,并改善其同步放电特性而出现峯电位。李卓荦用微电极法证明士的宁局部作用能抑制皮质的突触电位与树突电位。

Twenty-four adult rabbits(body weight 1500—2000 gm),under light urethane ana- thesia(1 gm/kg),were subjected to craniotomy.The symmetrical areas of the parietal cortex were exposed and each side was covered by a filter paper which had been soaked with any one of the following drugs:(1)2% Strychnine(Sulphate),(2) 1‰ Stry- chnine,(3)20% KCI,(4)2% KCl.The normal saline was used for the controls. Thirty minutes later,all animals were killed by decapitation.The cortical areas were rapidly removed within one minute and stained with the following method:(1)Gomori's method for acid phosphatase(ACP),(2)Unna's method for ribonucleic acid(RNA), and(3)Toluidine blue stain for Nissl bodies.The cevical cord(C3-4)was also re- moved in some animals and stained for RNA.In five animals,the EEG records were obtained from the cortical surface with the silver-silver chloride nonpolarized electrodes. The EEG results confirmed the established experiments that when 20% KCl was placed locally,the amplitudes of the EEG waves became markedly decreased,while 2% Stry- chnine was applied,the typical 'Strychnine Spikes'appeared consistently. The local application of 20% KCl did not produce any significant effect on the RNA contents of the horizontal cells(Cajal's cells)in the lst layer.But the pyramidal cells of the 2nd,3rd layers exhibited a typical central chromatolysis,i.e.,RNA decreased or disappeared,nucleus became eccentric,Nissl bodies underwent dissolution.The granu- lar cells of the fourth layer also showed central chomatolysis,but less marked.The ganglion cells and polymorphic cells in 5th,6th layers did not differ apparently from that of the normal saline controls.2% KCl produced the similar effect although the de- generative changes were not so severe as compared with that of the 20% KCl. Local application of 2% Strychnine did not alter the RNA levels of the Cajal cells. The RNA content of pyramidal cells in 2nd—3rd layers decreased to a considerable de- gree,but the typical chromotalytical changes were absent.The RNA of the large pyramidal cells in the 5th layer appeared as clusters of large granules.The RNA levels of 4th,6th layer showed no considerable changes as compared with that of the normal saline controls,1‰ Strychnine had no significant effect on the RNA content of the cere- bral cortex. The RNA of the anterior horn cells of the cevical cord was the same as the control animals no matter what drugs had been applied. 20% KCl enhanced the ACP reaction of the whole cortex,especially the 2nd—3rd layers.2% KCl produced the same effect but to a lesser degree.1% Strychnine also increased the ACP activities of the 2nd—4th layers.But 1‰ Strychnine had no signifi- cant effect. Based on the mentioned results,the significance of RNA and ACP for the functions and the functional relations of nerve cells between cortical neurons were discussed.