Correlations between glycine incorporation and cerebral cortical activity

3H-glycine was applied on the acoustic cortex of cats at different levels of anaesthesia and its incorporation into the cortical cells was studied using light microscopic autoradiography. Glycine was incorporated only by nerve cells. The extent of incorporation depended on the level of activity: it was most intensive in waking cortices and diminished gradually with deepening of anaesthesia. In light barbiturate anaesthesia, when only spontaneous spindles were present in the electrocorticogram, labelling was restricted to layers I-III of the cortex. Acoustic click stimulation intensified and extended it to layer V. It seems that glycine incorporation reflects neuronal activity with the resolution of an extracellular microelectrode.