Maturational changes in postictal refractoriness and seizure susceptibility in developing rats

The ability of the central nervous system to suppress recurrent seizures as a function of age was determined in rats. Eight electrical stimulations were delivered to the amygdala at 2-minute intervals in adult and suckling rats that were previously kindled from the left amygdala. During this 16-minute period, prolonged and severe convulsions were repeatedly elicited in the 16-day-old rat pups, whereas convulsions were not always elicited in adult rats. The results suggest that immature rats are more prone to develop status epilepticus than adult rats. Subsequently, the rat pups and implanted but not stimulated littermates were allowed to grow. At maturity, all the surviving animals were kindled from the contralateral (right) amygdala. The previously kindled rats developed seizures significantly faster than did their littermates. However, their respective abilities to suppress recurrent seizures did not differ at 150 and 210 days of age, being similar to the seizure suppression abilities of naive controls and significantly greater than those evidenced in infancy. We conclude that the propensity to develop single seizures in adulthood is directly related to infant seizure history, whereas the ability to suppress multiple seizures is a dynamic process that is modified by age, being minimal early in life and enhanced with maturation independently of history of infantile convulsions.