Effect Of Acute Hypotension On 5-HT And 5-HT_1AR In The Medial Vestibular Nucleus In Conscious Rats

Vestibular nucleus is located at brain stem, which can take part in its body space movement, posture adjustment and it is also closely related to the sympathetic function activities. Vestibular nucleus formed by multiple nucleis, one primary nuclei of medial vestibular nucleus (MVN) is not only both sides of the vestibular nuclei fiber communication information integration, but also an important target of vestibular-sympathetic reflection. For present the studies of vestibular reaction few of vestibule-sympathetic reflect.Vestibule-sympathetic reflexes (VSR) shows the change of heart rate, respiration, blood pressure when the vestibular organs stimulated, in turns the change of blood pressure affect the vestibule. Our previous research also found that glutamate (Glu) and its receptor take part in vestibular nerve nuclear activities in conscious rats induced by acute hypotension. It has proved that serotonin (5-hydroxytryptamine,5-HT) participate vestibular nucleus activities. It was found that MVN of 5-HT associated with vertigo by hot and cold water in vivo micro penetration technology monitoring guinea pigs. But it is unknown whether MVN of 5-HT and 5-HT1AR participate in vestibular nerve nuclear activities in conscious rats induced by acute hypotension of SNP.Therefore, in order to investigate the role of 5-HT and 1A receptor of vestibular nuclei excitation induced by SNP of conscious rats, we used high performance liquid chromatography (HPLC), immunohistochemistry and Western Blotting to observe.Results as follows:1. The vestibular symptoms was loss balance after UL:the head deviation appeared at 24h, the peak time of 72h without restore; spontaneous nystagmus appeared at 24h, reduced at 48h and then disappeared at 120h; the body rolling appeared at 6h after drug injected, reduced at 12h and the second peak time at 72h then disappeared at 168h.2. The level of 5-HT contents was increased obviously in MVN following SNP-induced acute hypotension in conscious rats (P< 0.05, n=12).3. The level of 5-HT contents increased obviously in contralateral MVN (P< 0.05, n=12) compared with control group, but not in ipsilateral MVN (P> 0.05, n=12) after UL two weeks by SNP-induced acute hypotension in conscious rats.4. There was a significant expression of 5-HT immunoreactive neuron in MVN compared with control group by intravenous infusion of SNP in conscious rats (P< 0.05, n=6).5. Compared with ipsilateral MVN, the expression of 5-HT immunoreactive neurons in contralateral MVN following SNP-induced acute hypotension 80 min of UL conscious rats have a significant difference(P< 0.05, n=6).6. There was a significant expression of 5-HT1AR immunoreactive neuron in MVN compared with control group by intravenous infusion of SNP in conscious rats (P< 0.05, n=6).7. Compared with ipsilateral MVN, the expression of 5-HT1AR immunoreactive neurons in contralateral MVN following SNP-induced acute hypotension 80 min of UL conscious rats have a significant difference(P< 0.05, n=6).8. There was a significant expression of 5-HT1AR protein in MVN compared with control group by intravenous infusion of SNP in conscious rats (P< 0.05, n=6).9. There was a significant expression of 5-HT1AR protein between contralateral and ipsilateral MVN following SNP-induced acute hypotension 80 min of UL conscious rats(P< 0.05, n=6).These results indicated that:The SNP-induced acute hypotension influence the activity of the neurons in the MVN,5-HT and 5-HT1AR may be involved in this process.