[Ultrastructural bases of neuron "epileptization" and brain "convulsive readiness"].

Ultrastructure of the neurons of an epileptic focus in patients with cerebral tumors accompanied by epilepsy (group 1--40 observations) and the cortex adjacent to the tumor without epilepsy (group 2--20 observations) was studied. The results of electron microscopic examinations of these cases were compared. Ultrastructural changes of the neurons in both groups were found to be nearly identical, with the exception of changes in axodendritic synapses: in group 1 their mass activation was moderate, in group 2 poorly manifested. It is concluded that mass activation of axodendritic synapses should be considered to be the morphological substrate of neuronal "epileptization". The steady activation of axodendritic synapses in the interattack period is, in all probability, the structural basis of the so-called convulsive readiness of the brain to reiterated attacks.