Effects of Nasal Inhalation of Peppermint Oil on Mental Fatigue Behaviors and Amino Acid Neurotransmitters in Mice

Objective To investigate the influence of nasal inhalation of peppermint oil on mental fatigue behaviors and amino acid neurotransmitters in mice.Methods Male KM mice were divided into blank control group,distilled water control group,sleep deprived model group and peppermint oil group.Forced swimming test and pentobarbital sodium induced sleeping test were used to observe the changes in emotion and sleep of mice.After 48-hour sleep deprivation by the method of water standing,mice were subjected to open field test for the observation of spontaneous activity of the mice.The levels of amino acid neurotransmitters of aspartate(Asp),glutamic acid(Glu),glycine(Gly),gamma aminobutyric acid(GABA)in the olfactory bulb,hypothalamus and cortex of the sleep-deprived mice were detected by precolumn derivative dinitrofluorobenzene HPLC(RP-DNFB-HPLC) within 2h after medication of peppermint oil.Results Compared to the blank control group,the immobility time in forced swimming test and the sleeping time in pentobarbital sodium induced sleeping test were significantly shortened after the treatment with peppermint oil.Compared to the sleep deprived model group,the spontaneous activity of sleep deprived mice in peppermint oil group was dramatically increased,Asp content in the olfactory bulb and hypothalamus was promoted remarkably in 10 min and began to fall in 30 min,Gly stayed unchanged while Glu/GABA was elevated dramatically in the three cerebral regions and then went down after a peak at 15 min.The results of correlation analysis showed that Asp and Glu contents in the olfactory bulb were markedly correlated with those in the hypothalamus and cortex within 2 hours after treatment.Conclusion Nasal inhalation of peppermint oil has anti-mental fatigue effect on mice,and its mechanism may depend on the regulation of amino acid neurotransmitters in the cerebral regions related to mental fatigue through olfactory system.