EFFECT OF AGE ON PENTYLENETETRAZOL-KINDLING AND KINDLING-INDUCED IMPAIRMENTS OF LEARNING-PERFORMANCE

Epileptogenesis during ontogeny may not be linearly related to time. I t is known that the behavioral manifestations of seizures are age-depe ndent, but more research is needed to clarify ontogenetic aspects of e pilepsies and related alterations, including cognitive deficits. Kindl ing is an accepted animal model for the study of the convulsive compon ent of epilepsy and its consequences on behavior. Recently, we demonst rated an impairment in acquisition of a conditioned reaction in young adult kindled rats, using pentylenetetrazol (PTZ) as the kindling stim ulus. The present study was undertaken to investigate the dependence o n age of alterations in the induction of PTZ kindling in rats. We star ted the kindling protocol in 4-, 6-, and 8-week- and 6-, 12-, 18-, and 24-month-old rats. The PTZ kindling showed an age-dependent decrease in expression of convulsions. The diminished kindling capacity was alr eady seen in 6-month-old rats. In contrast, kindling-related impairmen t effects on cognitive functions increased with age. Thus, the correla tion between learning impairment and occurrence of tonic-clonic seizur es that we had demonstrated in 8-week-old rats was abolished in older rats. On the other hand, when the kindling procedure was started in 6- week-old rats, no impairment was found in fully kindled rats. (C) 1997 Elsevier Science Inc.