| There are many reports indicating the existence of a vestibulo-sympathetic pathway that can counterbalance and adjust alterations of the blood pressure evoked by changing gestures through vestibule-sympathetic reflex and a feed-forward mechanism. This circuit may involves the direct projection of the vestibular nuclear (VN) to the Rostral ventrolateral medullar (RVLM) and the indirect pathway of the nucleus tractus solitarius (NTS) the indirect circuit. Anatomical and electrophysiological researches demonstrated that the vestibular nucleus has an autonomic nucleus group which can directly project to the brain stem for regulation of cardio-vasculature. The autonomic nucleus group includes nucleus solitary, nucleus vagus, nucleus ambiguus, Rostral ventrolateral medulla and caudal medulla. It is well known that the baroreceptor plays a pivotal role in maintaining blood pressure by negative feedback regulation. NTS is an important sensory relay nuclei in the baroreceptor pathway by sense the signal coming from the braches of glossopharyngeal nerve and vagus nerve. Previously we had demonstrated that acute hypotension could induce the activity of the vestibular nuclei, and also could increase the protein expression of c-Fos and p-ERK1/2. Thus, NTS may receive signals not only from the baroreceptor, but also from the nucleus vestibular in vestibular-sympathetic reflex. AIM:In this study, to investigate the possible role of vestibular-VN-NTS in blood pressure regulation, a sinoaortic denervation (SAD) rat model was used. After administration of phenylephrine (PE) and sodium nitroprusside (SNP), the heart rate, blood pressure and baroreflex sensitivity (BRS) of the rat model were evaluated. The expressions of c-Fos and p-ERK1/2were also evaluated by immunohistochemistry staining.RESULTS:1.Trace the sinus nerve of the rat, where it joins the hypoglossal nerve from the bifurcation of the internal carotid artery inclined inwardly. The sinus nerve is easy to distinguish since its arrangement is solely, but the arrangement of the aortic nerve appears some variation. Among the86rats, the sinus nerve of the rest60rats (about70%) runs parallel between the vagus nerve and cervical sympathetic nerve, and finally joins the laryngeal nerve;2. Intravenous PE administration in the SAD group increased heart rate rather than decreased it compared to SHAM group and normal group (P<0.05, n=8). Intravenous SNP administration in SAD group increased the heart rate with lower amplitude when compared to SHAM group and normal group (P<0.05, n=8).3. Intravenous SNP and PE administration in SAD group significantly decreased BRS when compare to SHAM group and normal group (P<0.05, n=8).4. In the setting of SNP administration in normal rats, the c-Fos expression initiated, followed by increasing expression, reaching the peak level and significantly coming down at the time30min,60min,90min and120min post-administration respectively, which statistically significant when compared to saline administration group (P<0.05, n=6).5. The expression of c-Fos in NTS of Bilateral labyrinthectomy(BL) group, BL+SAD group and SAD group significantly decreased at90min after SNP induced acute hypotension, compared to the SHAM group (P<0.01, n=6); the expression of c-Fos significantly decreased in BL+SAD group when compared to SAD group and BL group (P<0.01, n=6); the expression of c-Fos significantly decreased in SAD group when compared to BL group (P<0.01, n=6).6. The expression of p-ERKl/2in NTS of normal rats is observed at5min,10min,20min and40min post SNP induced hypotension, with a peak level at10min.7. Compared to the SHAM group, the p-ERKl/2expression in NTS of BL group, SAD group and BL+SAD group were significantly decreased at10min after SNP induced acute hypotension (P<0.05, n=6); the p-ERK expression of BL+SAD group was markedly decreased when compared to the BL and SAD group (P<0.05, n=6); the p-ERKl/2expression of BL group was markedly decreased when compared to the SAD group (P<0.05, n=6).CONCLUSION:1. The method of sinoaortic denervation (SAD) in conscious rats can be used for studies of central mechanisms underlying blood pressure regulation. 2. It is hypothesized that there may have vestibular-VN-TNS blood pressure regulation pathway in the CNS. |
