A depressant cortical reaction induced by afferent stimulation.
A depressant reaction of the electrocortical activity of the brain cortex is described. The changes consist in decrease in the amplitude and frequency of the basal waves of the electrocorticogram together with the appearance of slow waves similar to those of the sleep state. The results are more clear upon the dendritic action potentials induced by the topical application of strychnine or mescaline. They include a rise in the threshold to the electrical stimulation applied to elicit these potentials together with a lengthening of their latencies. The depressant effects were obtained by low threshold vagal, carotid sinus, low threshold sciatic and tactile afferent stimulation. Similar depressant effects were produced by serotonin (5-HT) topically applied. The effects of afferent stimulation were reduced in magnitude by an intracisternal injection of 5,6-dihydroxytryptamine. A serotonergic mechanism acting in a diffuse, humoral, way is postulated. The methodological importance of studying the strychnine or mescaline spikes is emphasized.