The effects of neurotoxicants on kindling and kindled seizures

The application of a constant-amplitude electrical stimulation to many parts of the brain leads to the expression of progressively more severe epileptiform responses. The process of acquisition is termed kindling, and the acquired response is termed the kindled seizure. This state has been used in a number of important ways including the modeling of human epilepsy and behavioral disorders, the testing of drugs for anticonvulsant effects, and, more recently, the examination of hyperexcitability states induced by pesticides and other environmental chemicals. This report discusses attributes of kindling and kindled seizures, examines possible mechanisms responsible for them, and summarizes drug and chemical effects on them. Kindling is powerfully accelerated by exposures to only a few substances, among the most effective of which are the chlorinated hydrocarbon insecticides, lindane and dieldrin. An analysis of the acceleration of kindling produced by lindane suggests that the threshold concentration in the nervous system for kindling enhancement is approximately 0.4 microgram/g (1.4 X 10(-9) mol/g).