Involvement of a Critical Development Period

Kindled seizures are widely used as a model for epi-leptogenesis. Although the achievement of kindlingcriterion is known to require time to develop, theprecise developmental period has not been identified.We now report that optimal achievement of the kin-dling criterion in the Sprague-Dawley rat is associatedwith a critical inter-stimulus interval of 24 to 26 days.We show that highly efficient kindling can beachieved with only two subconvulsive doses of pen-tylenetetrazole so long as they are given 25 days apart.Using Northern blot hybridization we show that theincreased seizure susceptibility at 25 days coincideswith an increased expression of the plasticity-associ-ated proteins, growth-associated protein-43 (GAP-43),microtubule-associated protein 1B (MAP1B), and tis-sue plasminogen activator (tPA) mRNAs in the hip-pocampus. By