The central nervous stimulating effect of four different halogenated ether anesthetics and halothane in mice.

Although enflurane is a convulsive anesthetic, its structural isomer, isoflurane, is believed not to be. We reported previously that, unexpectedly, isoflurane more frequently produced opisthotonus in young mice, especially during the induction period, than enflurane. In the present study, we examined the incidences of opisthotonus induced by four halogenated ether anesthetics and halothane to evaluate their CNS stimulating actions. As experimental animals, we used young male mice, with another two aged groups of male mice to clarify the relationship of the incidence of opisthotonus to aging. The percentage incidence of opisthotonus was 93% for sevoflurane, 81% for isoflurane, 64% for enflurane, 17% for methoxyflurane and 2% for halothane. These results suggest that the halogenated ether anesthetic, which is rapidly uptaken by the CNS during induction, is more likely to produce CNS stimulation, subsequently leading to opisthotonus. There was no age related susceptibility difference to anesthetic-induced opisthotonus, except for enflurane, in which the incidence of opisthotonus was higher in the aged group.