Effect Of Glutamate On The MVN-NTS-RVLM Projection After Sodium Nitroprusside-Induced Hypotension In Conscious Rats

Vestibular organs which is in inner ear could perceive body movement and the position of head in space and induce the vestibulo-ocular, vestibulo-spinal and vestibulo-autonomic nervous reflex, vestibulo-autonomic nervous reflex also is called vestibule-visceral reflex. Baroreflex is the neuroregulation form of regulating blood pressure. Vestibular organs takes the signal from the eighth cranial nerves to VN to affect blood pressure through cardiovascular regulation-baroreflex. Additionally, NTS receives inputs from a variety of central nervous system regions, including the caudal portion of the vestibular nucleus complex. And labyrinthine inputs could affect the lots of homeostatic responses, part of responses could be mediate through projections from the vestibular nuclei to the NTS at the least. In the process of posture changing,vestibulo-sympathetic reflex mediated the distribution of blood. The RVLM could integrate the inputs from NTS and PVN, transfered these information to the sympathetic sensory neuron in intermediolateral column of spinal cord to finished regulating the cardiovascular activity through exciting or inhibiting sympathetic nerve system.According to the research, following SNP-induced acute hypotension in normal rats, the pERK1/2 and c-Fos immunoreactive neurons increased in the RVLM. But in BL rats, the pERK1/2 and c-Fos immunoreactive neurons decreased significantly. These showed that vestibular organ participated in the process of acute hypotension exciting the neurons in the RVLM. But in this process, the functional relationships between the MVN and NTS, RVLM have still unknown. And it has not cleared that whether ionotropic glutamate receptors play a role in the activation of the NTS and RVLM. Whether ionotropic glutamate receptors affected that hypotension excited the neurons in NTS and RVLM, has not seen the reports.In the research, the methods of pharmacological and immunohistochemistry were used. In SAD rats, we will discuss whether NTS and RVLM participate in the vestibular blood pressure regulation. During the blood pressure regulation of vestibular system, the MVN-NTS-RVLM pathway which regulates the blood pressure may be existed or not and expound the effect of ionotropic glutamate receptors in the MVN-NTS-RVLM reflex pathway. Try to clarify the possibility of MVN-NTS-RVLM pathway in vestibular cardiovascular regulation path.Results:1.Activity of SAD rats decreased significantly, feeding and water intake also decreased. But blood pressure did not obviously change compared with the normal animals, but the blood pressure was not stable and vulnerable to external stimulus.2.After the microinjection of ACSF, Lidocaine, NMDA, AMPA, MK801 or CNQX into the MVN or NTS, the BP was stable than before, there was no significant difference; After SNP-induced acute hypotension, the BP were decreased than before significantly.3. After the microinjection of ACSF into the MVN, pERK1/2 and c-Fos positive neurons are all increased significantly. But in lidocaine group, the density of pERK 1/2 and c-Fos positive neurons declined in the NTS compared with the control group, (p <0.001.n=6).4. By microinjection of MK801 into the MVN, the density of pERK1/2 and c-Fos positive neurons in the NTS after SNP administration showed significantly decreases. There were significant differences (p<0.001,n=6)5. Microinjection of CNQX into the MVN inhibited the density of pERK1/2 and c-Fos positive neurons in the NTS after SNP administration (p<0.001,n=6)6.By microinjection of NMDA into the MVN, the density of pERK1/2 and c-Fos positive neurons in the NTS significantly increased to compare with the ACSF group. The differences was significant, (p< 0.001,n=6)7 In ACSF group the density of pERKl/2 and c-Fos positive neurons showed low level, but microinjection of AMPA into the MVN, the density of pERK1/2 and c-Fos protein in the NTS significantly increased. And the differences were significant. (p< 0.001,n=6).8.By microinjection of lidocaine into the NTS before injection the SNP, the density of pERK1/2 and c-Fos positive neurons in the RVLM declined significantly compared with the control groups (p<0.001,n=6)9. Microinjection of MK801 into the NTS before inducing hypotension, the density of pERK1/2 and c-Fos positive neurons in the RVLM showed significantly decreases. There were significant differences compared with the control groups (p< 0.001, n=6).10.After microinjection of CNQX into the NTS, the density of c-Fos and pERK1/2 positive neurons in the RVLM showed significantly decreases. There were significant differences (p<0.001,n=6)11. Microinjection of NMDA into the NTS increased the density of pERK1/2 and c-Fos positive neurons in the RVLM, and there were significant differences compared with the ACSF group (p< 0.001,n=6).12. By microinjection of AMPA into the NTS the density of pERK1/2 and c-Fos positive neurons increased significantly in the RVLM. There were differences significant compared with the ACSF group (p< 0.001,n=6)Conclusions:1. The pathway of the MVN-NTS-RVLM may be existed in the vestibular blood pressure regulation.2. NMDA and AMPA ionotropic glutamate receptors may participate in the vestibular blood pressure regulation.