Effects Of Ketamine And Myristicin On Stress Induced Mental Disorders And Their Related Mechanisms

Stress,proposed by Han Salyein the 1930s,is a comprehensive response state that occurs when the body is stimulated by drastic changes in the external environment,including neurological,mental,endocrine and immune system responses.The clinical manifestations of stress mental disorders are consciousness disorder,depression,anxiety,paranoia,overreaction of corresponding stressors,fear and so on.It is a general name of a kind of disease with stress as the main cause,including depression,anxiety,trauma and stress-related disorder.This study aims at the most common post-traumatic stress disorder（PTSD）and depression in stress mental disorders,and evaluates the effect and mechanism of ketamine in preventing and treating PTSD and myristicin antidepressant respectively,in order to explore the feasibility of them as new anti-PTSD drugs and antidepressants,and to clarify their pharmacological characteristics and mechanisms.ⅠStudy on the pharmacological effects and mechanism of ketamine in the prevention and treatment of post-traumatic stress disorder.Ketamine is a non-competitive glutamate N-methyl-D-aspartate（NMDA）receptor antagonist.A large number of scientific studies have shown that ketamine has a rapid antidepressant effect.Its optical isomer esketamine hydrochloride nasal spray was approved to market in the United States on March 5,2019,which made a breakthrough in the research of antidepressants.Due to the high co-prevalence of depression and PTSD and similar therapeutic drugs,the preventive and therapeutic effect of ketamine on PTSD has aroused widespread interest among researchers in recent years.Unfortunately,so far,no consistent conclusion has been reached on the therapeutic effect of ketamine on post-traumatic stress disorder,and there is also a lack of systematic research on the timing and duration of ketamine administration,so it is of great significance to study the effect and mechanism of ketamine on the prevention and treatment of PTSD.PurposesThe purpose of this study was to evaluate the effects of single administration of ketamine on the formation,expression,regression and retention of conditioned fear in PTSD model animals,and to study its mechanism based on the expression regulation of brain-derived neurotrophic factor（BDNF）,so as to provide experimental basis for expanding the clinical application of ketamine and elucidating the pharmacological characteristics of ketamine.MethodsBased on the above research purpose,we used the classical mouse conditioned fear model and rat time-dependent sensitized（TDS）to evaluate the effects of ketamine on scene fear and sound cue fear behavior and BDNF expression in rats and mice.To clarify the pharmacological characteristics of ketamine（effective dose,effective time,duration）and mechanism（which stage of fear memory plays a role,and whether it plays a role by regulating the expression of BDNF）.ResultsThe results of conditioned fear model in mice showed that:（1）A single dose of ketamine(10 mg·kg^-1)intraperitoneal injection（ip）at different time points（7 d,24 h or 0.5 h before training）had no significant effect on the formation of fear,the expression of contextual fear or the sound cue fear 24hour after training in mice.（2）A single dose of ketamine(3 mg·kg^-1or 10mg·kg^-1,i.p.)injected 0.5 h before fear training had no effect on the formation of fear memory,but ketamine at 10 mg·kg^-1had significant inhibitory effect on the expression of sound cues fear on the 7 th day and the expression of scene fear on the 14th day after fear training.（3）A single dose of ketamine(10 mg·kg^-1,i.p.)immediately after fear training had no significant effect on the expression of fear memory,（4）A single dose of ketamine(10 mg·kg^-1,i.p.)injected 0.5 h before fear expression test had no significant effect on the expression of cue fear memory.（5）A single dose of ketamine(10 mg·kg^-1,i.p.)at different stages of fear memory（before or after electric shock training,before or after extinction training）had no significant effect on the regression and retention of cue fear.（6）A single dose of ketamine(10 mg·kg^-1,i.p.)injected 0.5 h before fear training significantly reversed the decrease of cortical BDNF expression induced by fear 24 h and14 d after training.The results of rat TDS model showed that a single dose of ketamine(10mg·kg^-1,i.p.)injected 0.5 h before fear training significantly inhibited scene fear expression 24 h after training,and the same dose of ketamine injected 24h before fear training significantly inhibited sound cue fear expression 24 h afer training.ⅡStudy on the antidepressant effect and mechanism of myristicin.PurposesThe purpose of this study was to evaluate the antidepressant and rapid action characteristics of myristicin,and to evaluate whether its mechanism is related to the activation of 5-hydroxytryptamine（5-HT）system,norepinephrine system（NE）,glutamate（Glu）system,opioid system or cannabinoid system by traditional pharmacological methods.In the existing treatment of depression in China,chemical drugs play a leading role,but serious adverse reactions will occur due to long-term use of such drugs.Therefore,it has become the focus of researchers to find and develop ideal antidepressants from traditional Chinese medicine compound prescri.p.tions and natural products with less side effects.Nutmeg is a plant of the family nutmeg,the dry and mature kernel of nutmeg,which has a wide range of pharmacological effects,such as antidiarrheal,liver protection,anti-tumor,antioxidation,hypnosis and so on.Nutmeg has strong central activity,and overdose has hallucinogenic effect.Studies have shown that nutmeg extract may have antidepressant effect,but the mechanism has not been clearly reported.Myristicin is the main component of nutmeg volatile oil.In vitro studies have shown that it has moderate monoamine oxidase activity,but whether it has antidepressant effect has not been reported.MethodsBased on the above research purposes,this study used a variety of depression animal models,including behavioral despair model,chronic stress model and reserpine model to evaluate the antidepressant effects and characteristics of nutmeg.Furthermore,a variety of drug antagonistic models were used,including p-chlorophenylalanine（PCPA）depletion 5-HT test,5-hydroxytryptophan（5-HTP）induced head twitch test,yohimbine toxicity enhancement test,WAY100635 antagonism of 5-HT_1Areceptor test,NBQX antagonismofα-amino-3-hydroxy-5-methyl-4-isoxazolylpropionic acid（AMPA）.The effects of nutmeg on 5-HT system,NE system,5-HT_1Areceptor,AMPA receptor,opioid system and cannabinoid system were evaluated by AMPA receptor test,naloxone antagonistic opioid test,AM251antagonistic cannabinoid receptor CB1 test and AM630 antagonistic cannabinoid receptor CB2 test.ResultsThe results of the antidepressant effect of myristicin were as follows:（1）In the behavioral despair model of mice,a single dose of myristicin 3mg·kg^-1and10 mg·kg^-1（i.p.）or intragastric administration（i.g.）significantly reduced the immobility time of tail suspension and force swimming in mice.（2）The results of locomotor activity test in mice showed that the antidepressant dose of myristicin had no significant effect on the spontaneous activity of mice.（3）In the depression model induced by low dose reserpine,administration of myristicin 3 mg·kg^-1（i.g.）and 10 mg·kg^-1（i.g.）for two weeks significantly reversed the prolonged immobility of tail suspension or swimming in reserpine treated mice.The characteristics of rapid antidepressant effect of myristicin were studied.The results were as follows:（1）A single dose of myristicin 3mg·kg^-1（i.p.）and ketamine 10 mg·kg^-1（i.p.）significantly decreased the immobility time of tail suspension test and force swimming test 0.5 h and 24h after drug administration in mice,while duloxetine only had inhibitory effect on immobility time 0.5 h after drug administration.（2）In reserpine-induced depression model,single administration of myristicin 3mg·kg^-1（i.p.）and ketamine 10 mg·kg^-1（i.p.）si.g.nificantly increased sucrose preference in reserpine-treated mice;（3）In chronic stress model,after a single administration of 3 mg·kg^-1（i.p.）and 10 mg·kg^-1（i.p.）,sucrose preference in chronic stress model mice increased by 68%and 72%,respectively,but there was no statistical difference.The results of the study on the antidepressant mechanism of myristicin:（1）In the late experiment of 5-HT depletion by PCPA,the antidepressant effect of myristicin 3 mg·kg^-1in tail suspension and forced swimming test was completely abolished by PCPA.（2）In the 5-HTP induced head twitching test,a single dose of myristicin 3 mg·kg^-1（i.p.）reduced the number of 5-HTP-induced head twitching in a dose-dependent manner.（3）In the yohimbine toxicity test,myristicin 3 mg·kg^-1（i.p.）had no si.g.nificant effect on the mortality of mice induced by yohimbine.（4）In the WAY100635antagonistic 5-HT_1Areceptor test,the antidepressant effect of myristicin 3mg·kg^-1（i.p.）in the forced swimming test was completely abolished by WAY100635.（5）In NBQX antagonistic AMPA receptor experiment,NBQX had no antagonistic effect on antidepressant effect of myristicin 3mg·kg^-1（i.p.）in tail suspension test and forced swimming test in mice.（6）In naloxone antagonistic opioid receptor test,the antidepressant effect of myristicin 3 mg·kg^-1（i.p.）In forced swimming test was completely abolished by naloxone.（7）In the experiment of antagonizing cannabinoid receptor CB1 and CB2 by AM251 and AM630,the antidepressant effect of myristicin 3 mg·kg^-1（i.p.）in forced swimming test in mice was completely abolished by AM251 and AM630.