Kindling in developing rats: persistence of seizures into adulthood.

The effects of kindling induced in developing rat pups were re-examined when the rats reached maturity. Eighteen-day-old rats, implanted with bipolar electrodes, were separated into the following 4 groups: the fully kindled group consisted of pups that developed generalized convulsions; the partially kindled group of pups that consistently displayed afterdischarges and occasionally behavioral focal seizures; the afterdischarge group of pups in which the afterdischarge threshold was measured and the non-stimulated group of pups implanted but not stimulated. Subsequently, the electrodes were removed and the rats were allowed to grow. At 65-70 days, the surviving rats and age matched controls were rekindled. The vulnerability to kindled convulsions at maturity, as expressed by the kindling rates, correlated directly with the severity of previous kindled seizures, but did not correlate with the presence of long standing gliotic lesions. These findings suggest that the neural alterations evoked by kindling persist and are not modified by the dynamic changes that occur with growth.