Effect of glutamate on the vestibulo-solitary projection after sodium nitroprusside-induced hypotension in conscious rats.

Orthostatic hypotension is most common in elderly people, and its prevalence increases with age. Attenuation of the vestibulo-sympathetic reflex (VSR) is commonly associated with orthostatic hypotension. In this study, we investigated the role of glutamate on the vestibulo-solitary projection of the VSR pathway to clarify the pathophysiology of orthostatic hypotension. Blood pressure and expression of both pERK and c-Fos protein were evaluated in the nucleus tractus solitarius (NTS) after microinjection of glutamate into the medial vestibular nucleus (MVN) in conscious rats with sodium nitroprusside (SNP)-induced hypotension that received baroreceptor unloading via sinoaortic denervation (SAD). SNP-induced hypotension increased the expression of both pERK and c-Fos protein in the NTS, which was abolished by pretreatment with glutamate receptor antagonists (MK801 or CNQX) in the MVN. Microinjection of glutamate receptor agonists (NMDA or AMPA) into the MVN increased the expression of both pERK and c-Fos protein in the NTS without causing changes in blood pressure. These results indicate that both NMDA and AMPA receptors play a significant role in the vestibulo-solitary projection of the VSR pathway for maintaining blood pressure, and that glutamatergic transmission in this projection might play a key role in the pathophysiology of orthostatic hypotension.

Analysis of the Baroreceptor and Vestibular Receptor Inputs in the Rostral Ventrolateral Medulla following Hypotension in Conscious Rats.

Input signals originating from baroreceptors and vestibular receptors are integrated in the rostral ventrolateral medulla (RVLM) to maintain blood pressure during postural movement. The contribution of baroreceptors and vestibular receptors in the maintenance of blood pressure following hypotension were quantitatively analyzed by measuring phosphorylated extracellular regulated protein kinase (pERK) expression and glutamate release in the RVLM. The expression of pERK and glutamate release in the RVLM were measured in conscious rats that had undergone bilateral labyrinthectomy (BL) and/or sinoaortic denervation (SAD) following hypotension induced by a sodium nitroprusside (SNP) infusion. The expression of pERK was significantly increased in the RVLM in the control group following SNP infusion, and expression peaked 10 min after SNP infusion. The number of pERK positive neurons increased following SNP infusion in BL, SAD, and BL+SAD groups, although the increase was smaller than seen in the control group. The SAD group showed a relatively higher reduction in pERK expression when compared with the BL group. The level of glutamate release was significantly increased in the RVLM in control, BL, SAD groups following SNP infusion, and this peaked 10 min after SNP infusion. The SAD group showed a relatively higher reduction in glutamate release when compared with the BL group. These results suggest that the baroreceptors are more powerful in pERK expression and glutamate release in the RVLM following hypotension than the vestibular receptors, but the vestibular receptors still have an important role in the RVLM.

Additive role of the vestibular end organ and baroreceptors on the regulation of blood pressure in rats.

Contribution of the vestibular end organ to regulation of arterial pressure was quantitatively compared with the role of baroreceptors in terms of baroreflex sensitivity and c-Fos protein expression in the rostral ventrolateral medulla (RVLM). Baroreflex sensitivity and c-Fos protein expression in the RVLM were measured in conscious rats that had undergone bilateral labyrinthectomy (BL) and/or baroreceptor unloading. BL attenuated baroreflex sensitivity during intravenous infusion of sodium nitroprusside (SNP), but did not significantly affect the sensitivity following infusion of phenylephrine (PE). Baroreflex sensitivity became positive following sinoaortic denervation (SAD) during infusion of PE and attenuated sensitivity during infusion of SNP. Baroreflex sensitivity also became positive following double ablation (BL+SAD) during infusion of PE, and attenuated sensitivity during infusion of SNP. c-Fos protein expression increased significantly in the RVLM in the sham group after SNP administration. However, the BL, SAD, and SAD+BL groups showed significant decreases in c-Fos protein expression compared with that in the sham group. The SAD group showed more reduced c-Fos protein expression than that in the BL group, and the SAD+BL group showed less expression than that in the SAD group. These results suggest that the vestibular system cooperates with baroreceptors to maintain arterial pressure during hypotension but that baroreceptors regulate arterial pressure during both hypotension and hypertension. Additionally, afferent signals for maintaining blood pressure from the vestibular end organs and the baroreceptors may be integrated in the RVLM.

Multicomponent (Ce, Cu, Ni) oxides with cage and core-shell structures: tunable fabrication and enhanced CO oxidation activity.

Solvothermal synthesis of Cu2O cubes from Cu(OAc)2 in ethanol provided templates for tunable formation of novel multicomponent composites: hollow CeO2-Cu2O (), core-shell NiO@Cu2O () and hollow CeO2-NiO-Cu2O (). Composites catalyze the oxidation of CO at a lower temperature than the parent Cu2O cubes.

Comparative analysis of vestibular receptor and baroreceptor inputs to the nucleus tractus solitarius following acute hypotension in conscious rats.

Blood pressure is maintained by the interaction between the arterial baroreflexes and the vestibulo-cardiovascular reflexes during postural changes. In this study, the influence of the vestibular receptors on the maintenance of blood pressure following acute hypotension was quantitatively compared with the role of baroreceptors in terms of c-Fos protein expression in the nucleus tractus solitarius (NTS). Expression of c-Fos protein in the NTS was measured in conscious rats that had undergone bilateral labyrinthectomy (BL) and/or sinoaortic denervation (SAD). Expression of c-Fos protein increased significantly in the NTS in the sham group after sodium nitroprusside (SNP) administration. However, the BL, SAD, and SAD+BL groups showed significant decreases in c-Fos protein expression compared to that of the sham group. The SAD group showed relatively more reduction in c-Fos protein expression than the BL group, and the SAD+BL group showed the least expression among the three experimental groups. The c-Fos protein expression in the NTS following acute hypotension was localized to the caudal portions of the nuclei in the BL and SAD groups. These results suggest that the role of vestibular receptors in maintaining blood pressure following acute hypotension is less potent than that of the baroreceptors but more potent than other afferent inputs in conscious rats. In addition, afferent signals for maintaining blood pressure originating from the vestibular receptors and the baroreceptors may converge in the caudal portion of the NTS.

[Source apportionment of nitrogen and phosphorus from cropping non-point source pollution in Nansi Lake basin].

Field runoff pools were used to collect the field surface runoff samples of different cropping systems in Nansi Lake region, and different forms of nitrogen (N) and phosphorus (P) data were analyzed. The source profiles of N and P in different cropping systems were also obtained by summarizing the experimental data measured in the current study. Samples were also collected from the 11 main rivers of Nansi Lake basin and the concentrations of N and P were determined. Principle component analysis (PCA) was applied to obtain cropping non-point pollution sources of N and P. The result showed that three types of N and P contamination sources were apportioned in Nansi Lake basin, explaining 95.275% of the total variance. The first source was from field surface runoff of wheat-maize rotation with a wide pollution range and a larger contribution, and it contributed 50. 220% of the total contamination burden; the second type of N and P source was the water runoff pollution from garlic-maize rotation, were 25.119% contribution; the third source was the surface runoff from wheat-rice rotation, and it contributed 19.937%.