Mechanism Of The NMDA Receptor For Excitement Of Vestibular Nucleus Induced By Hypotension In The Acute Stage Of Vestibular Organ Damage

Studies have reported that intravenous injection of sodium nitroprusside during induced acute hypotension in anesthetized animals, blood flow of the Peripheral vestibular organs decreased with blood pressure lower,to increase vestibular nerve afferent impulses and release Excitatory neurotransmitter- glutamate, thus excited medial vestibular nucleus and could evoke c-fos protein expression in medial vestibular nucleus (MVN). In this study, we used immunohistochemistry and pharmacological methods, in the acute phase of vestibular organ damage with conscious rats observed during acute hypotension c-Fos protein expression in the medial vestibular nucleus, and discussed possible receptor mechanism of Glu-NMDA.Results as follows:1.In intact labyrinthine group,there were significant expression of cFL immunoreactive neurons bilaterally in the MVN following SNP-induced acute hypotension in intact labyrinthine conscious rats, but in the control group a few numbers of cFL immunoreactive neuron were expressed in the MVN. Difference between the two group was significant (P<0.001)2.There were significant expression of cFL immunoreactive neurons in contralateral MVN to the lesion side following unilateral chemical labyrinthectomy 6h,12h,24h,48h and 72h later, expression of cFL immunoreactive neurons peaked at 48h in contralateral MVN to the lesion side in conscious rats. During after unilateral chemical labyrinthectomy 48h intravenous injection SNP, There were significant expression of cFL immunoreactive neurons in contralateral MVN to the lesion side, there was significant difference between experiment group and control group(P<0.001).3.After intracerebroventricular microinjection 60 min of NMDA, there were significant expression of cFL immunoreactive neurons bilaterally in the MVN of intact labyrinthine conscious rats. But in the control group few numbers of cFL immunoreactive neuron was expressed in the MVN after intracerebroventricular microinjection of artificial cerebrospinal fluid(ACSF) of intact labyrinthine conscious rats. There was significant difference between control group and NMDA group of intact labyrinthine conscious rats (P<0.001).4.In the control group, after intracerebroventricular microinjection of ACSF, there were significant expression of cFL immunoreactive neurons bilaterally in the MVN following SNP-induced acute hypotension 60 min of intact labyrinthine conscious rats. But after intracerebroventricular microinjection of a NMDA receptor antagonist of glutamate(MK-801), few numbers of cFL immunoreactive neuron was expressed in the MVN after SNP-induced acute hypotension 60 min of intact labyrinthine conscious rats. There was significant difference between control group and MK-801 group of intact labyrinthine conscious rats (P<0.001).Conclusion:Vestibular nuclues neurons were excited by acute hypotension during the acute stage of unilateral peripheral vestibular organ damage in conscious rats, which was probably mediated by the NMDA receptor.