Development of an experimental model of epilepsy in rats exposed to ozone

Paroxysmal activity has been reported in the olfactory bulb of rabbits chronically exposed to ozone (O-3), postulating that this gas provokes alterations in the electrical activity of the central nervous system. The effects of 1 ppm of O-3 inhaled daily for 1 or 3 h prior to each stimulation were studied using the kindling model of epilepsy. Results showed that O-3 decreased the duration of the amygdaloid after-discharges during the development of kindling and shortened the latency to the onset of the first generalized seizure in rats exposed for 1 h to O-3, while the group exposed for 3 h also decreased the after-discharge duration but delayed the appearance of seizures. Spread of seizure activity, defined as the latency to reach behavioral and electrographic signs of tonic clonic seizures was faster in the 1 h O-3 exposed rats and slower in those exposed for 3 h. These findings demonstrate that O-3 or its reaction products, such as free radicals, could affect the mechanisms involved in kindling course, such changes being dependent of the time of O-3 exposure. (C) 1997 Elsevier Science Ireland Ltd.