The ontogenesis of cortical self-sustained after-discharges in rats.

An ontogenetic development of cortical self-sustained after-discharges (SSADs) was studied in acute experiments on 98 male albino rats aged from 9 days to adulthood. Rhythmic electrical stimulation of one cortical sensorimotor area regularly elicited SSADs formed by spike-and-wave complexes starting from the postnatal day 15. Frequency of these complexes increased from 2.0 to 2.5 cycles/s in 15- and 18-day-old rats to 3.0 to 4.0 cycles/s in older animals. In younger animals SSADs were better expressed in the stimulated sensorimotor than in the visual area of both hemispheres, whereas in older rats the SSADs were fully generalized. The SSADs became longer with increasing age. A highly significant prolongation of the SSADs was seen in all age groups with repeated stimulations; this finding is discussed as a possible form of kindling.