Effect Of Rostral Ventrolateral Medulla In The Blood Pressure Regulation Of Vestibular System Participation And The Mechanism Of Neurochemistry

After vestibular organs sense body movement and the head position in space, it not only causes the reflex of the vestibule-ocular and vestibule-spinal, but also induces vestibule-visceral reflex through some intermediate nuclei. A lot of studies suggest that the baroreflex-independent vestibule-sympathetic reflex pathways exist in various species. The baroreflex is the most important feedback mechanisms in the blood pressure (BP) regulation. A series of studies by Yates and his co-workers has demonstrated that the signals coming from peripheral vestibular organs via vestibular nucleus(VN) could affect BP through the classic pathway of cardiovascular regulation. the baroreflex. Baroreflex sensitivity (BRS) is an index that evaluates the sensitivity of heart rate changes caused by BP changes, and can reflex the functional status of cardiovascular automatic nervous system. It is well known that the rostral ventrolateral medullar (RVLM) plays a critical role in the sympathetic tone regulation and BP control. RVLM region is considered as a key area which is in the path of conveying vestibular signals to gray substance of spinal cord. However. the exact reflex pathway and its central neurotransmitter remain unclear.In this study, we investigated the vestibular cardiovascular pathway of vestibular system participated-baroreceptor reflex regulation through RVLM during acute hypotension, the roles of RVLM in the vestibular system participated-BP regulation and its neurochemistry mechanisms after bilateral labyrinthectomy (BL) or sinoaortic denervation (SAD) by microdialysis, high performance liquid chromatography (HPLC) and immunohistochemical methods in anesthetic or conscious rats. The aim of this study is to clarify the possibility of the existence of vestibular cardiovascular pathway, which is the vestibular organ-vestibular nucleus-the RVLM.Results:1. Compared with BL, SAD and SAD+BL groups, the basal level of MAP and HR was no significant difference in Sham group (P>0.05, n=8);2. Intravenous injection of PE, the BRS in BL group was no significant difference than Sham group (P>0.05, n=8), whereas, the mean values of BRS in SAD and SAD+BL groups was positive, which was significant difference than Sham and BL group (P<0.05, n=8).3. Intravenous injection of SNP, the mean values of BRS in BL, SAD and SAD+BL groups were significantly decreased than Sham group (P<0.05, n=8). The mean values of BRS in SAD and SAD+BL group were lower than BL group (P <0.05, n=8), and the mean value of BRS in SAD+BL group was lower than SAD group (P<0.05, n=8).4. Compared to intravenous injection of saline in the non-operation rats,30min,60min,90min and120min after intravenous injection of SNP-induced acute hypotension, the expression of cFL immunoreactive neurons in the RVLM was significant increased, and was peaked at90min (P<0.05, n=6).5. After90min of SNP-induced acute hypotension, the expresion of c-Fos protein in RVLM in BL, SAD and SAD+BL groups were greatly decreased than the Sham group (P<0.05, n=6). The expression of c-Fos protein in RVLM in SAD and SAD+BL groups was less than BL group(P<0.05, n=6), and in SAD+BL group was less than SAD group (P<0.05, n=6).6. Compared to intravenous injection of saline in the non-operation rats,5min,10min,20min and40min after intravenous injection of SNP-induced acute hypotension, the expression of pERK protein in the RVLM was significant increased, and was peaked at10min (P<0.05, n=6).7. After10min of SNP-induced acute hypotension, the expression of pERK protein in RVLM in BL, SAD and SAD+BL groups were greatly decreased than the Sham group (P<0.05, n=6). The expression of pERK protein in RVLM in SAD and SAD+BL groups was less than BL group(P<0.05,n=6), and in SAD+BL group was less than SAD group (P<0.05, n=6).8. The basal level of excitatory amino acids-ASP and Glu. and inhibitory amino acid-Gin in each experimental group there was no significant difference(P>0.05); but in the SAD and SAD+BL group, the inhibitory amino acid-Gly. Tau and Ala were significantly reduced compared with control group and BL (P<0.05)9. SNP-induced acute hypotension accompanied with an increase in the level of excitatory amino acids:ASP and Glu, and a decrease in the level of inhibitor amino acids:Gly, Tau and Ala in the RVLM (P<0.05vs. basal level, n=6);10. The increased excitatory amino acids and the decreased inhibitory amino acids after SNP-induced acute hypotension in BL and SAD groups were significantly lower than Sham group (P<0.05,n=6). The change in SAD group was less than BL group (P<0.05, n=6). However, there was no significant change in amino acid in SAD+BL group before and after SNP-induced acute hypotension.(P>0.05. n=6). in group,Conclusions:1. The vestibular system may participate the regulation of BP through the RVLM.2. BL and SAD decrease the basal content of Gly, Tau and Ala in the RVLM.3. Some amino acids such as excitatory amino acids, Asp and Glu. inhibitor amino acids Ala, Gly, Ala and Tau may be involved in the vestibular system participated-BP regulation.