Number of synaptic vesicles in the rat somatosensory cortex after repetitive electrical stimulation prolonging self-sustained after-discharges.

The sensorimotor area of the cerebral cortex of rats was repetitively electrically stimulated (8 Hz for sec) at 10-min intervals, inducing a gradual prolongation of self-sustained after-discharges (SSADs). At 10 min after termination of the third SSAD, the animals were perfused with a fixation solution. The homotopic area of the contralateral hemisphere was examined in the electron microscope. In the II cortical layer, the agranular synaptic vesicles in type I synapses (after Gray) were counted close to the synaptic cleft. The number of synaptic vesicles was significantly increased in the experimental animals.