Intracellular phenomena in electrically induced seizures

Abstract Intracellular recordings were made from both pyramidal tract cells and non-pyramidal tract cells is the motor cortex of the cat. The responses elecited by single stimuli to the cortical surface or to the medullary pyramid were found to change during and after electrically induced seizures. Similar slow changes in the membrane potentials during and after seizures occurred in both types of cells but spikes superimposed on the smooth or oscillatory depolarization were more frequently observed in pyramidal tract elements. In these, antidromic spikes could be elicited during and after a seizure except when either marked depolarization occurred or when the stimulus fell in the refractory period. Responses characterized by a depolarizing wave (EPSP) could be generated by single stimuli during and after a seizure except towards the termination of the seizure. Responses characterized by a hyperpolarizing wave (IPSP) were never obtained by single shocks during and immediately after a seizure. The development, maintenance and termination of experimental epileptic seizure have been discussed on the basis of the above results.