Effects of streptomycin on the cortical neurons in the cat

Data concerning the effects of streptomycin application on the brain cortex are very scarce and nonconcordant, despite routine intra-thecal administration of this drug. Experiments peformed in 15 adult cats permitted us to observed that application of streptomycin sulphate on the brain cortex leads to a real cortical depression, demonstrated by the disappearance of spontaneous spikes, lack of cortical fast activity and lack of hippocampal theta activity. The direct cortical response disappears too and sometimes even the transmission towards the deep structures of neuronal activation induced by high intensity or repetitive stimuli. The depressing activity of streptomycin resembles to a spreading depression, with an effect limited only to the hemisphere where the drug is applied. The difference between our results and those of other authors can be explained by the different degree of purity of the streptomycin used in the experiments.