Effect Of UL On The Glu Release And C-Fos Protein Expression In The Medical Vestibular Nucleus Of Conscious Rats

Vestibular apparatus controls posture and movement.Excitation of peripheral vestibular receptors by the changes of posture and movement transmit to vestibular nucleus(VN).The activity of the VN by the afferent impilses from peripheral vestibular receptors takes part in keeping balance with visual sensation and somatic sensation.Unilateral labyrinthectomy(UL)is the animal model of the plasticity in central nervous system diseases.The vestibular symptoms were observed after infusing arsanilic acid.Some of these symptoms gradually disappeared over time,but others continued.It is called vestibular compensation.Asymmetric expression of c-Fos protein in the bililateral MVN during acute vestibular compensation and disappear about 6 day in anaesthetic rats following UL(Park et al,1999).Our previous study observed that lidocaine can influence the activity of the MVN by the afferent impilses from vestibular organ,and asymmetric release of glutamate in the MVN of anaesthetic rats following lidocaine unilateral infusion in middle ear,glutamate could be participate in vestibular compensation.However,the detailed role of glutamate in the MVN following UL of conscious rats was not investigated and the detailed mechanism of receptor is still not clear.Therefore,in order to investigate temporal changes of release of glutamate and c-Fos protein following UL of conscious rats,and effect of NMDA receptor,we used Microdialysis Technique and High Performance Liquid Chromatography(HPLC),Immunohistochemistry(IHC)and Western Blotting(WB).Results as follows:1.After UL,the high incidence of spontaneous nystagmus appeared at 24 h after UL,then reduced and disappeared at 120 h.The head deviation gradually augmented,the peak time appeared at 120 h,and did not restore until 168 h.The body rolling appeared from 6 h,and the peak time appeared at 96 h after UL,then reduced and disappeared at 168 h.2.6 h after UL,the release of glutamate in extracellular fluid of contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric release of glutamate(p<0.05,n=6).And 24,12 h after injection,the release of glutamate in extracellular fluid of contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric the release of glutamate(p<0.05,n=6).Asymmetric release of glutamate recurred at 72h.Asymmetric release of glutamate was at 6.12.24.48、72、96 h、120h after UL in bililateral MVN(p<0.05,n=6.The release of glutamate in extracellular fluid of MVN almost recovered at 144 h.3.6 h after UL,the amount of c-Fos immunoreactive positive neurons in contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric expression of c-Fos immunoreactive positive neurons(p<0.05,n=6).And 24,12 h after injection,the amount of c-Fos immunoreactive positive neurons in contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric expression of c-Fos immunoreactive positive neurons(p<0.05,n=6).Asymmetric expression recurred at 72h.Asymmetric expression of c-Fos immunoreactive positive neurons was at 6、12、24、48、72、96 h、120 h after UL in bililateral MVN(p<0.05,n=6.The amount of c-Fos immunoreactive positive neurons in the MVN almost disappeared at 144 h.4.6 h after UL,the expression of c-Fos protein in contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric expression of c-Fos protein(p<0.05,n=6).And 24,12 h after injection,the expression of c-Fos protein in contralateral MVN significantly higher than the ipsilateral MVN,showing asymmetric expression of c-Fos protein(p<0.05,n=6).Asymmetric expression recurred at 72h.Asymmetric expression of c-Fos protein was at 6、12、24、48、72、96 h、120 h after UL in bililateral MVN(p<0.05,n=6.The amount of c-Fos protein in the MVN almost disappeared at 144 h.5.72 h after UL,MK-801 of intracerebroventricular injection,There was significant difference between control group and MK-801 group(p<0.05,n=6).These results suggest that:Glutamate maybe participated in the MVN of conscious rats during vestibular compensation,and induced the expression of c-Fos protein via NMDA receptor.Further more,it took part in vestibular compensation.