Functional Relationship Between The MVN And RVLM During The Vestibular Blood Pressure Regulation

Previous studies showed that acute hypotension induced by sodium nitroprusside (SNP) could excite the afferent nerve which originated from peripheral vestibular organ, and then change the function of the medial vestibular nucleus (MVN) and the rostral ventrolateral medulla (RVLM). But the functional relationship between the MVN and the RVLM during this process is still unknown. And it is not clear that whether ionotropic glutamate receptors play an important role in the activation of the RVLM during acute hypotension just like its role in the activation of MVN.Experimental methods:In order to explore the functional link between the MVN and RVLM, as well as to clarify the mechanism of glutamate receptors during the vestibular blood pressure regulation following acute hypotension, we designed this study. First, we microinjected lidocaine and glutamate receptor antagonists into the MVN of the sinoaortic denervation (SAD) model rats with pharmacological methods, and immunohistochemical methods were used to detect the expression of c-Fos and pERK protein in the RVLM following acute hypotension induced by intravenous injection of SNP. Then, the expression of c-Fos and pERK protein was observed within the RVLM after the microinjection of glutamate receptor agonists in the MVN.Results:1. After the microinjection of lidocaine in the MVN, the acute hypotension-induced c-Fos and pERK protein expression in the RVLM were decreased. Compared to the control group which had been microinjected with artificial cerebrospinal fluid (ACSF) into the MVN (hypotension was followed), they had significant difference (P<0.05, n=6). 2. After the microinjection of Glu receptor antagonist (MK-801) in the MVN, the acute hypotension-induced c-Fos and pERK expression protein in the RVLM were decreased. Compared to the control group which had been microinjected with ACSF into the MVN (hypotension was followed), they had significant difference (P<0.05, n=6).3. The expression of c-Fos and pERK protein in the RVLM induced by microinjection of Glu receptor agonist(NMDA) in the MVN were increased. Compared to the control group which had been microinjected with ACSF into the MVN, they had significant difference (P<0.05, n=6).4. After the microinjection of Glu receptor antagonist (CNQX) in the MVN, the acute hypotension-induced c-Fos and pERK protein expression in the RVLM were decreased. Compared to the control group which had been microinjected with ACSF into the MVN (hypotension was followed), they had significant difference (P<0.05, n=6).5. The expression of c-Fos and pERK protein in the RVLM induced by microinjection of Glu receptor agonist(AMPA) in the MVN were increased. Compared to the control group which had been microinjected with ACSF into the MVN (no hypotension), they had significant difference (P<0.05, n=6).Conclusions:MVN and RVLM play important roles in the vestibular blood pressure regulation, which is involved in NMDA and AMPA receptors.