Effects of Prolonged Optic Nerve Tetanization on Lateral Geniculate Potentials

¹ From the Laboratories of Clinical Science and Neurophysiology, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland

Tetanization of the optic nerve at 500/sec. for periods varying from 5 seconds to 6 minutes produced a long lasting (hours) second subnormality of the postsynaptic lateral geniculate response in nembutalized cats. Optic nerve tetanization for 10 minutes or longer did not produce a second subnormality. When such a prolonged tetanus was applied during previously induced second subnormality, this subnormality was abolished. Tetanization for 10 minutes or longer did not prevent the occurrence of second subnormality produced by a subsequently applied shorter (0.5 min.) tetanus. Second subnormality did not occur following tetanization of the optic nerve in unanesthetized decerebrate cats. This finding suggests that the metabolic changes associated with Nembutal anesthesia were of importance in the occurrence of second subnormality.