| Motion sickness(MS)is a multi-system physiological response caused by exposure on abnormal acceleration stimulus.The initial symptoms of MS mainly include anorexia,pale,lethargy,cold sweat,etc,which is followed by stimuli and autonomic nervous reactions,some serious symptoms such as nausea,salivation,vomiting and hypothermia may occur.In animal experiments,MS can cause anorexia,gastrointestinal reactions(conditioned gaping and defecation response),hypoactivity,and hypothermia.The literature reports that the Orexin system in the lateral hypothalamic area(LHA)play an important role in the regulation of feeding,autonomic nervous system,cardiovascular system,circadian rhythm,physical activity and thermoregulatory.The Orexin-A(OXA)have many regulatory functions,such as increase food intake,reduce nausea and vomiting,increase locomotor activity,and regulates body temperature.These effects are contrary to the symptoms of MS.It has been clarified that the symptoms of MS are closely related to vestibular visceral reflex.However,whether the Orexin system participate in vestibular visceral reflex or has a alleviate effect on autonomic symptoms in MS hasn't been reported.Therefore,in our study,we will produce two different chemical vestibular lesion models,to observe the behavioral abnormalities(including vestibular deficit syndrome,the exploratory behavior,spontaneous activity in the cage)and the changes of the Orexin expression in models.Then,to determine the relationship between Orexin system activity and vestibular behavioral abnormalities after vestibular lesions,we will use the Orexin receptor inhibitor in the models and observe the behavioral changes.Secondly,with the intracerebroventricular injection of the OXA,to observe the effects on the symptoms in MS rats.With the Fos-IL neurous expression changes in hypothalamic and brainstem regions,to identify which nucleus may play a role in OXA;microinjection of OXA,Orexin receptor(OX1R)inhibitor and cannabinoid type 1 receptor(CB1R)inhibitor in the regions which may associated with motion sickness in hypothalamus,then observe the changes of the symptoms of motion sickness in rats.Finally,through the retrograde labeling of fluoro-gold(FG),observe the anatomical pathway between the brainstem neurous and the relevant regions of the hypothalamus.Contents:1.To observe the changes in behavior abnormalities and Orexin expression in rats with vestibular lesions.Two different models of chemical vestibular lesion were produced(injection of sodium arsanilate by the intra-tympanic membrane and injection of 3'3-iminodipropionitrile by intraperitoneal)to observe the vestibular behavioral abnormalities(including circling,retropulsion,abnormal head movements,air-righting reflex,tail-hanging reflex),Spontaneous locomotor activity in the cage and The exploratory behavior;immunohistochemical method was used to observe the changes of Orexin-Labled neurous expression in the LHA2.To observe the effect of OX1 R inhibitor SB334867(SB)on behavioral abnormalities caused by vestibular lesions.3.To observe the effect of exogenous OXA on relief the symptoms related to motion sicknessRadioimmunoassay was used to observe the changes of OXA levels in rats' cerebrospinal fluid during motion sickness and its adaptation.The cerebral ventricle was used to observe the symptoms of MS,including anorexia,conditioned gaping,defecation response,spontaneous activity reduction and hypothermia;the expression of Fos protein in the hypothalamic and plant nerve-associated nuclei in the brainstem was observed by immunohistochemical ABC method to identify the relevant nucleus of OXA.4.The related regions in the hypothalamus were injected with OXA and OXR inhibitors to observe changes in anorexia,conditioned gaping,defecation response,spontaneous activity and hypothermia in MS rats5.The related regions in the hypothalamus were injected with CB1 R inhibitors to observe the effect of OXA on the relief of MS symptoms6.Injected with FG for retrograde labeling to observe the anatomical pathways of the autonomic-related nuclei and hypothalamic regions.Results:1.Both vestibular lesion models showed obvious vestibular behavioral abnormalities,accompanied by obvious spontaneous activity in the cage and hypeactivity in the open field.Immunohistochemistry revealed the lateral hypothalamic area of the two models.The number of Orexin-Lable neurons increased significantly in LHA.The i.c.v injection of the OX1 R antagonist significantly attenuated the vestibular deficit syndrome,hypeactivity in the home cages and the open field induced by vestibular lesions animals.2.After rotation stimulated for 10 days,the levels of OXA in cerebrospinal fluid was significantly increased in rats.I.c.v injection of exogenous OXA can dose-dependently relief the symptoms in anorexia,conditioned gaping,defecation response,hypoactivity and hypothermia;OX1R inhibitor can dose-dependently block the action of OXA to alleviate the symptoms of MS,including anorexia,conditioned gaping,defecation response and hypoactivity;and i.c.v injection of Orexin type 2 receptor inhibitor TCS-OX2-29 can block OXA to relief hypothermia symptoms in model rats.Immunohistochemical results showed that the expression of Fos protein was significantly increased in the solitary tract nucleus(NTS),parabrachial nucleus(PBN),Locus Coeruleus(LC),paraventricular nucleus of the hypothalamic(PVN)and dorsomedial nucleus of the hypothalamic,ventral part(DMV)in the model animals;After i.c.v injection of OXA,the number of Fos-IL neurous was significantly increased in the premammillary nucleus,ventral part(PMV),LC,and dorsomedial nucleus of the hypothalamic,dorsal part(DMD),and reduced in PVN,DMV.3.To inject the OXA in the hypothalamus of model rats,we found that OXA was injected in the dorsomedial nucleus of hypothalamic(DMH)can significantly alleviate the symptoms of anorexia and hypactivity;in the PVN can reduce the conditional gaping;and the PMV can be used after injection of OXA significantly alleviate the symptom of hypothermia.After pretreatment with the OX1 R inhibitor in DMH and PVN,can significantly block the OXA alleviation of anorexia,spontaneous activity and conditioned gaping in MS rats.PMV injection of OX2 R inhibitor can block the alleviation of hypothermia by OXA.After pretreatment with injection of CB1 R inhibitor in DMH,it can significantly block the alleviate effect of OXA on anoraxia,and pretreatment in PMV can significantly block the effect of OXA on hypothermia.4.Retrograde tracing results showed that FG-immunoreactive neurons can be found in PBN and NTS after the FG injected in DMH and PMV.However,after injected in the PVN,only PBN was observed.Conclusion:1.The chemical vestibular lesion can significantly increase the number of Orexin-Labled neurons in LHA.OX1 R inhibitor can significantly alleviate the vestibular behavioral abnormalities,locomotor activities and the explotary behavior in vestibular lesion rats.These results suggested that the elevated OXA activity might play a role in vestibular loss-induced locomotor deficits and hyperkinesia.2.I.c.v injection of OXA can significantly alleviate the symptoms of anorexia,gastrointestinal reactions(conditional gaping and defecation response),dyskinesia(spontaneous activity reduction)and hypothermia in rats which caused by MS,and the activity of neurous in DMV and PVN was decreased.Otherwise,the activity of neurous in DMD and PMV was increased.3.Exogenous OXA relieves the symptoms of anorexia and spontaneous activity by stimulating OX1 R in DMH;reduce nausea and vomiting by stimulating OX1 R in PVN;relieves hypothermia symptoms by stimulating OX2 R in PMV.OXA may also activate CB1 R in the reverse direction,which can alleviate the anorexia and hypothermia symptoms of MS.4.There is a direct projection relationship between NTS and DMH,PMV;and a direct projection relationship between PBN and DMH,PVN,PMV.It indicates that the vestibular visceral stimulation signal can directly affect the activity of the above-mentioned related nuclei of the hypothalamic autonomic nerve during MS. |
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