EFFECTS OF NITROUS OXIDE ON THE EPILEPTOGENIC PROPERTY OF ENFLURANE IN CATS

A method was developed to standardize the induction of seizure activity during enflurane anaesthesia in cats. The effects of nitrous oxide on the epileptogenic property of enflurane were investigated. A potent anticonvulsant action of nitrous oxide was noted, but partial tolerance to this effect rapidly developed. Some evidence of withdrawal hyperexcitability was also detected. The changes induced by nitrous oxide, despite wri«ting enflurane anaesthesia, suggest that these two anaesthetic agents have different sites or mechanisms of Enflurane has been shown to produce generalized seizures which may be evoked by a variety of sensory stimuli, some of which may be trivial (Botty et al., 1968; Linde et al., 1970; Joas, Stevens and Eger, 1971; Mori, 1973). More recent studies have re-ported on the nature (Moorthy et al., 1980) and origin (Meyers and Shapiro, 1978) of this epilep-togenic effect, and its facilitation or depression by various physiological and pharmacological changes, including hyper- and hypocapnoea (Neigh, Garman and Harp, 1971; Lebowitz, Blitt and Dillon, 1972), diazepam (Darimont and Jenkins, 1977), thiopen-tone (Furgang and Sohn, 1977), and other anti-convulsant drugs (Schettini and Wilder, 1974). Enflurane has been shown to produce a dose-related decrease in reticular neuronal firing (Mori, 1973) and an increase in magnitude of the sensory stimulus-evoked potential (SEP) (Clark, Hosick an