The effect of hypergravity exposure for two weeks on propofol anesthesia in rats

Abstract

General anesthesia in space flight is a big challenge for now. To achieve this, understanding the influence of gravitational change on central nervous system (CNS) modulation is required, however it is still unclear. The vestibular system is known to be a highly plastic organ. Previous studies reported that the hypergravity exposure induced plastic alteration of the glutaminergic and GABAergic system via the vestibular system. We hypothesized that hypergravity exposure‐induced CNS modulation might change the effectiveness of anesthetic agent. To clarify this hypothesis, we examined the effect of the intravenous propofol anesthesia in rats reared in 1 G and 3 G environments for 14 days. We measured electroencephalogram (EEG), electrical stimulation‐induced pressor response, propofol metabolism, and GABAA β2/3 subunits in the brain. EEG data showed that the hypnotic effect of propofol (20mg/kg) in 3 G rats was prolonged (43.7 ± 2.9 min) than that in 1 G (26.0 ± 1.0 min) rats. This effect was completely abolished by vestibular lesion (29.7 ± 1.6 min) in 3 G rats. Since there was no difference in propofol metabolism among groups, hypergravity exposure might alter the sensitivity of the propofol via vestibular system.