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Vestibular Activation Habituates the Vasovagal Response in the Rat

Vasovagal syncope is a significant medical problem without effective therapy, postulated to be related to a collapse of baroreflex function. While some studies have shown that repeated static tilts can block vasovagal syncope, this was not found in other studies. Using anesthetized, male Long–Evans...

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Autores principales: Cohen, Bernard, Martinelli, Giorgio P., Xiang, Yongqing, Raphan, Theodore, Yakushin, Sergei B.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350135/
https://www.ncbi.nlm.nih.gov/pubmed/28360882
http://dx.doi.org/10.3389/fneur.2017.00083
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author Cohen, Bernard
Martinelli, Giorgio P.
Xiang, Yongqing
Raphan, Theodore
Yakushin, Sergei B.
author_facet Cohen, Bernard
Martinelli, Giorgio P.
Xiang, Yongqing
Raphan, Theodore
Yakushin, Sergei B.
author_sort Cohen, Bernard
collection PubMed
description Vasovagal syncope is a significant medical problem without effective therapy, postulated to be related to a collapse of baroreflex function. While some studies have shown that repeated static tilts can block vasovagal syncope, this was not found in other studies. Using anesthetized, male Long–Evans rats that were highly susceptible to generation of vasovagal responses, we found that repeated activation of the vestibulosympathetic reflex (VSR) with ±2 and ±3 mA, 0.025 Hz sinusoidal galvanic vestibular stimulation (sGVS) caused incremental changes in blood pressure (BP) and heart rate (HR) that blocked further generation of vasovagal responses. Initially, BP and HR fell ≈20–50 mmHg and ≈20–50 beats/min (bpm) into a vasovagal response when stimulated with Sgv\S in susceptible rats. As the rats were continually stimulated, HR initially rose to counteract the fall in BP; then the increase in HR became more substantial and long lasting, effectively opposing the fall in BP. Finally, the vestibular stimuli simply caused an increase in BP, the normal sequence following activation of the VSR. Concurrently, habituation caused disappearance of the low-frequency (0.025 and 0.05 Hz) oscillations in BP and HR that must be present when vasovagal responses are induced. Habituation also produced significant increases in baroreflex sensitivity (p < 0.001). Thus, repeated low-frequency activation of the VSR resulted in a reduction and loss of susceptibility to development of vasovagal responses in rats that were previously highly susceptible. We posit that reactivation of the baroreflex, which is depressed by anesthesia and the disappearance of low-frequency oscillations in BP and HR are likely to be critically involved in producing resistance to the development of vasovagal responses. SGVS has been widely used to activate muscle sympathetic nerve activity in humans and is safe and well tolerated. Potentially, it could be used to produce similar habituation of vasovagal syncope in humans.
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spelling pubmed-53501352017-03-30 Vestibular Activation Habituates the Vasovagal Response in the Rat Cohen, Bernard Martinelli, Giorgio P. Xiang, Yongqing Raphan, Theodore Yakushin, Sergei B. Front Neurol Neuroscience Vasovagal syncope is a significant medical problem without effective therapy, postulated to be related to a collapse of baroreflex function. While some studies have shown that repeated static tilts can block vasovagal syncope, this was not found in other studies. Using anesthetized, male Long–Evans rats that were highly susceptible to generation of vasovagal responses, we found that repeated activation of the vestibulosympathetic reflex (VSR) with ±2 and ±3 mA, 0.025 Hz sinusoidal galvanic vestibular stimulation (sGVS) caused incremental changes in blood pressure (BP) and heart rate (HR) that blocked further generation of vasovagal responses. Initially, BP and HR fell ≈20–50 mmHg and ≈20–50 beats/min (bpm) into a vasovagal response when stimulated with Sgv\S in susceptible rats. As the rats were continually stimulated, HR initially rose to counteract the fall in BP; then the increase in HR became more substantial and long lasting, effectively opposing the fall in BP. Finally, the vestibular stimuli simply caused an increase in BP, the normal sequence following activation of the VSR. Concurrently, habituation caused disappearance of the low-frequency (0.025 and 0.05 Hz) oscillations in BP and HR that must be present when vasovagal responses are induced. Habituation also produced significant increases in baroreflex sensitivity (p < 0.001). Thus, repeated low-frequency activation of the VSR resulted in a reduction and loss of susceptibility to development of vasovagal responses in rats that were previously highly susceptible. We posit that reactivation of the baroreflex, which is depressed by anesthesia and the disappearance of low-frequency oscillations in BP and HR are likely to be critically involved in producing resistance to the development of vasovagal responses. SGVS has been widely used to activate muscle sympathetic nerve activity in humans and is safe and well tolerated. Potentially, it could be used to produce similar habituation of vasovagal syncope in humans. Frontiers Media S.A. 2017-03-15 /pmc/articles/PMC5350135/ /pubmed/28360882 http://dx.doi.org/10.3389/fneur.2017.00083 Text en Copyright © 2017 Cohen, Martinelli, Xiang, Raphan and Yakushin. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Neuroscience
Cohen, Bernard
Martinelli, Giorgio P.
Xiang, Yongqing
Raphan, Theodore
Yakushin, Sergei B.
Vestibular Activation Habituates the Vasovagal Response in the Rat
title Vestibular Activation Habituates the Vasovagal Response in the Rat
title_full Vestibular Activation Habituates the Vasovagal Response in the Rat
title_fullStr Vestibular Activation Habituates the Vasovagal Response in the Rat
title_full_unstemmed Vestibular Activation Habituates the Vasovagal Response in the Rat
title_short Vestibular Activation Habituates the Vasovagal Response in the Rat
title_sort vestibular activation habituates the vasovagal response in the rat
topic Neuroscience
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350135/
https://www.ncbi.nlm.nih.gov/pubmed/28360882
http://dx.doi.org/10.3389/fneur.2017.00083
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