Anesthetic sensitivity to isoflurane and changes in neurotransmitter in rats with motion sickness

Objective To explore changes in anesthetic sensitivity to isoflurane in rats with motion sickness,so as to provide evidence for rational application of isoflurane during deployment at sea.Methods Conditioned taste aversion (CTA) was used as a criterion of motion sickness and the rat model of motion sickness was developed by using the Crampton rotation simulator.(1) Two tests were made in the study,one was the anesthetic sensitivity test and the other was the neurotransmitter test.In the anesthetic sensitivity test,60 SD rats were randomly divided into the control group (n =15) and the rotation group (n =45).Changes in behavior and autonomic activity,the isoflurane concentration required for the rats to fall asleep or into an anesthesia state were closely observed.(2) In the neurotransmitter test,32 SD rats were randomly divided into 4 groups:the control group,the rotation group,the anesthesia group and the rotation plus anesthesia group,eachconsisting of 8 rats.Levels of acetylcholine (Ach),norepinephrine (NE),γ-aminobutyric acid (GABA)and glutamic acid (Glu) in the brain cortex,thalamus and hippocampus of the animals in the 4 groups were determined respectively.Results For the rats in the control group,the isoflurane concentration required for the animals to fall asleep or into an anesthesia state and the time required for the animals to return to consciousness from anesthesia were (1.06 ± 0.07) ％,(1.99 ± 0.04) ％ and (7.30 ± 1.12) min respectively.The isoflurane concentration required for the rats in the rotation group to fall asleep or into an anesthesia state and the time required for the animals to return to consciousness from anesthesia were (0.91 ±0.05) ％,(1.77 ± 0.04) ％ and (10.70 ± 2.79) min respectively.When compared with the control group,the isoflurane level required for the rats in the rotation group to fall asleep or into an anesthesia state was obviously lower,while on the other hand the time for the rats in the rotation group to return to consciousness from anesthesia was significantly longer (P ＜ 0.01).For the animals in the anesthesia group,changes in the levels of neurotransmitters were the main features,which was particularly significant in the brain cortex and thalamus (P ＜ 0.01),and for the animals in the rotation group,the level of Ach in the brain cortex elevated significantly,while the levels of NE and GABA in the hippocampus decreased obviously.Changes in the above data for the animals in the rotation plus anesthesia group were quite similar to those of the rotation group,with rotation stimulus presenting a more prominent effect.Conclusions Rats with motion sickness were obviously more sensitive to isoflurane,the mechanism of which required further study. Key words: Motion sickness; Anesthesia; Isoflurane; Neurotransmitters; Rats