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1 Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA; Faculty of Health Science, University of Western Ontario, London, ON, Canada
2 Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA
3 Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USa
4 Department of Otolaryngology, University of Colorado Health Sciences Center, Denver, CO, USA
5 Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USa
* To whom correspondence should be addressed. E-mail: byates{at}pitt.edu.
Prior studies have shown that removal of vestibular inputs produces lability in blood pressure during orthostatic challenges. Furthermore, these studies led to the prediction that the blood pressure instability results in susceptibility for orthostatic intolerance. The present experiments tested this hypothesis by recording common carotid blood flow (CCBF) in conscious cats during head-up tilts of 20°, 40°, and 60° amplitudes, before and after the surgical elimination of labyrinthine inputs through a bilateral vestibular neurectomy. Prior to vestibular lesions in most animals, CCBF remained stable during head-up rotations. Unexpectedly, in 5 of 6 animals, the vestibular neurectomy resulted in a significant increase in baseline CCBF, particularly when the laboratory was illuminated; on average, basal blood flow measured when the animals were in the prone position was 41±17 (SE) % higher after the first week following the lesions. As a result, even when posturally-related lability in CCBF occurred after removal of vestibular inputs, blood supply to the head was not lower than when labyrinthine inputs were present. These data suggest that vestibular influences on cardiovascular regulation are more complex than previously appreciated, as labyrinthine signals appear to participate in setting basal rates of blood flow to the head in addition to triggering dynamic changes in the circulation to compensate for orthostatic challenges.
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  K. J. Yavorcik, D. A. Reighard, S. P. Misra, L. A. Cotter, S. P. Cass, T. D. Wilson, and B. J. Yates Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2009; 297(6): R1777 - R1784. [Abstract] [Full Text] [PDF]
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