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 (O3), postulating that this gas provokes alterations in the electrical activity of the central nervous system. The effects of 1 ppm of O3 inhaled daily for 1 or 3 h prior to each stimulation were studied using the kindling model of epilepsy. Results showed that O3 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 O3, 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 O3 exposed rats and slower in those exposed for 3 h. These findings demonstrate that O3 or its reaction products, such as free radicals, could affect the mechanisms involved in kindling course, such changes being dependent of the time of O3 exposure.