Function-dependent glycine incorporation into neurons of the cat motor cortex

Filter papers soaked with 3H-2-glycine solution were applied to the motor cortex of chloralosed and nembutalized cats for one hour. Then underlying cortical samples were excised, fixed in Bouin solution and processed for light-microscopic autoradiography. Sections stained with haematoxylin-eosin were made to determine total cell counts. The cortical samples were sectioned in series so that 10 micron sections at every 50 micron were preserved. From resting and stimulated cortices 10 sections were used for counting pyramidal cells and interneurons in different layers. The electric background activity and the potentials evoked by thalamic VL and antidromic PT stimulation were recorded and averaged. In chloralose anaesthesia, only 7%, while under nembutal 22% of the cells incorporated glycine, on the average. VL stimulation, which induced the appearance of typical evoked potentials, enhanced the glycine incorporation of pyramidal cells in layers II-III and Vb and some activation in the interneurons of layer II was also seen. Antidromic PT stimulation did not change the autoradiographic pattern in chloralosed preparations, while in nembutalized cats it depressed the labelling of pyramidal cells in layers II, III and Va drastically with some enhancement in interneurons of layer II. The changes of autoradiographic patterns are in harmony with theories about cortical effects of VL and antidromic PT stimulation.