Korean J Physiol Pharmacol.  2014 Aug;18(4):353-358. 10.4196/kjpp.2014.18.4.353.

Effect of Vestibulosympathetic Reflex and Baroreflex on Expression of pERK in the Nucleus Tractus Solitarius following Acute Hypotension in Conscious Rats

• Jiang X
• Lan Y
• Jin YZ
• Park JY
• Park BG
• Ameer AN
• Park BR

• KMID: 2285531
• DOI: http://doi.org/10.4196/kjpp.2014.18.4.353

Abstract

Control of blood pressure is maintained by the interaction between the arterial baroreflex and vestibulosympathetic reflex during postural changes. In this study, the contributions of vestibular receptors and baroreceptors to the maintenance of blood pressure following acute hypotension were compared in terms of phosphorylated extracellular regulated protein kinase (pERK) expression in the nucleus tractus solitaries (NTS). Expression of pERK in the NTS was measured in conscious rats that had undergone bilateral labyrinthectomy (BL) and/or sinoaortic denervation (SAD) 5, 10, 20, and 40 min following acute hypotension induced by sodium nitroprusside (SNP) infusion. Expression of pERK increased significantly in the NTS in the control group following SNP infusion, and the expression peaked at 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 in control group. The BL group showed a relatively higher reduction in pERK expression than the SAD group, and the pERK expression in the NTS was localized to the caudal portion of the nuclei in the BL and SAD groups. These results suggest that the vestibular receptors may play a key role in maintaining blood pressure following acute hypotension; thus, the vestibular system may contribute to compensate for orthostatic hypotension.

Keyword

Baroreceptor; Hypotension; Nucleus tractus solitarius; pERK; Vestibular receptor

MeSH Terms

Animals
Baroreflex*
Blood Pressure
Denervation
Hypotension*
Hypotension, Orthostatic
Neurons
Nitroprusside
Pressoreceptors
Protein Kinases
Rats*
Reflex*
Solitary Nucleus*
Nitroprusside
Protein Kinases

Figure

• 

  Fig. 1 Confocal microscopic findings in rhodamine-pallodin stained samples showing the effect of arsanilate on vestibular hair cells. Cilia in hair cells disappeared after treatment with arsanilate. (A) Ampulla of the posterior semicircular canal in control; (B) ampulla of the posterior semicircular canal 48 hours after treatment with arsanilate. Magnification=×400; scale bar=10 µm.

• 

  Fig. 2 Photomicrographs showing the effect of acute hypotension on pERK expression in the nucleus tractus solitarius following a 30% reduction in blood pressure that was induced by SNP infusion in conscious rats with intact labyrinths and baroreceptors. Expression of pERK was measured 5 (B), 10 (C), 20 (D), and 40 (E) min after SNP infusion. Control (A) received intravenous administration of saline at the same volume as SNP; NTS, nucleus tractus solitarius (the coordinate: 0.2 mm rostral to the obex). Scale bar=200 µm. a, b, c, d, and e represent higher magnification of the NTS in A, B, C, D, and E (Scale bar=100 µm).

• 

  Fig. 3 Temporal changes in pERK expression in the nucleus tractus solitarius following a 30% reduction in blood pressure that was induced by SNP in conscious rats with intact labyrinths and baroreceptors. Controls received intravenous administration of saline at the same volume as SNP; min indicates the number of minutes after SNP administration. There were 8 rats in each group. *indicates a significant difference from the control group (**p<0.01).

• 

  Fig. 4 Effect of acute hypotension on pERK expression in the nucleus tractus solitarius following a 30% reduction in blood pressure that was induced by SNP infusion in conscious rats with bilateral labyrinthectomy (BL), sinoaortic denervation (SAD), or both bilateral labyrinthectomy and sinoaortic denervation (BL+SAD). Expression of pERK was measured 10 min after SNP infusion. Sham, sham-treated. There were 8 rats in each group. *indicates a significant difference from the sham group (**p<0.01).

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