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INTEGRATIVE |
Departments of
1 Otolaryngology
2 Neuroscience, University of Pittsburgh, Pittsburgh, PA 15213, USA
3 Faculty of Health Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B9
4 Department of Otolaryngology, University of Colorado Health Sciences Center, Denver, CO 80262, USA
Previous experiments have demonstrated that the vestibular system contributes to regulating sympathetic nervous system activity, particularly the discharges of vasoconstrictor fibres. In the present study, we examined the physiological significance of vestibulosympathetic responses by comparing blood flow and vascular resistance in the forelimb and hindlimb during head-up tilt from the prone position before and after the removal of vestibular inputs through a bilateral vestibular neurectomy. Experiments were performed on conscious cats that were trained to remain sedentary on a tilt table during rotations up to 60 deg in amplitude. Blood flow through the femoral and brachial arteries was recorded during whole-body tilt using perivascular probes; blood pressure was recorded using a telemetry system and vascular resistance was calculated from blood pressure and blood flow measurements. In vestibular-intact animals, 60 deg head-up tilt produced 
20% decrease in femoral blood flow and 37% increase in femoral vascular resistance relative to baseline levels before tilt; similar effects were also observed for the brachial artery (25% decrease in blood flow and 38% increase in resistance). Following the removal of vestibular inputs, brachial blood flow and vascular resistance during head-up tilt were almost unchanged. In contrast, femoral vascular resistance increased only 6% from baseline during 60 deg head-up rotation delivered in the first week after elimination of vestibular signals and 16% in the subsequent 3-week period (as opposed to the 37% increase in resistance that occurred before lesion). These data demonstrate that vestibular inputs associated with postural alterations elicit regionally specific increases in vascular resistance that direct blood flow away from the region of the body where blood pooling may occur. Thus, the data support the hypothesis that vestibular influences on the cardiovascular system serve to protect against the occurrence of orthostatic hypotension.
(Received 3 May 2006;
accepted after revision 27 June 2006;
first published online 29 June 2006)
Corresponding author B. J. Yates: University of Pittsburgh, School of Medicine, Department of Otolaryngology, Eye and Ear Institute, Rm 519, Pittsburgh, PA 15213, USA. Email: byates{at}pitt.edu
This article has been cited by other articles:
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  M. Arshian, R. J. Holtje, L. A. Cotter, C. D. Rice, S. P. Cass, and B. J. Yates Consequences of postural changes and removal of vestibular inputs on the movement of air in and out of the lungs of conscious felines J Appl Physiol, July 1, 2007; 103(1): 347 - 352. [Abstract] [Full Text] [PDF]
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 T.-K. Lee, J. H. Lois, J. H. Troupe, T. D. Wilson, and B. J. Yates Transneuronal tracing of neural pathways that regulate hindlimb muscle blood flow Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2007; 292(4): R1532 - R1541. [Abstract] [Full Text] [PDF]
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