Effects of postural changes and removal of vestibular inputs on blood flow to the head of conscious felines

Wilson, Tim; Cotter, Lucy A; Draper, J. A.; Misra, Sunil P; Rice, Cory D; Cass, Stephen P.; Yates, Bill J.

doi:10.1152/japplphysiol.01585.2005

Cited by 24 publications

(20 citation statements)

References 22 publications

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“…The animals were trained over a period of Ն3 wk to remain sedentary, with the limbs fully extended, during whole body head-up tilts at an amplitude of 20°, 40°, or 60°. The acclimation procedures used in this study were identical to those employed in previous experiments (10,11,21,31,32). During recording sessions, a jacket with attached Velcro straps was placed around the torso; the straps were secured to the sides of the tilt table to prevent the position of the animal from shifting during tilting.…”

Section: Methodsmentioning

confidence: 99%

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Yavorcik¹,

Reighard²,

Misra³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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September 30, 2009; doi:10.1152 doi:10. /ajpregu.00551.2009 show that the vestibular system contributes to blood pressure regulation. Prior studies reported that lesions that eliminate inputs from the inner ears attenuate the vasoconstriction that ordinarily occurs in the hindlimbs of conscious cats during head-up rotations. These data led to the hypothesis that labyrinthine-deficient animals would experience considerable lower body blood pooling during head-up postural alterations. The present study tested this hypothesis by comparing blood flow though the femoral artery and vein of conscious cats during 20 -60°head-up tilts from the prone position before and after removal of vestibular inputs. In vestibular-intact animals, venous return from the hindlimb dropped considerably at the onset of head-up tilts and, at 5 s after the initiation of 60°rotations, was 66% lower than when the animals were prone. However, after the animals were maintained in the head-up position for another 15 s, venous return was just 33% lower than before the tilt commenced. At the same time point, arterial inflow to the limb had decreased 32% from baseline, such that the decrease in blood flow out of the limb due to the force of gravity was precisely matched by a reduction in blood reaching the limb. After vestibular lesions, the decline in femoral artery blood flow that ordinarily occurs during head-up tilts was attenuated, such that more blood flowed into the leg. Contrary to expectations, in most animals, venous return was facilitated, such that no more blood accumulated in the hindlimb than when labyrinthine signals were present. These data show that peripheral blood pooling is unlikely to account for the fluctuations in blood pressure that can occur during postural changes of animals lacking inputs from the inner ear. Instead, alterations in total peripheral resistance following vestibular dysfunction could affect the regulation of blood pressure.blood flow patterning; venous return; cardiac output; orthostatic hypotension HEAD-UP BODY ROTATIONS in humans or animals typically result in some pooling of blood in the periphery and a resulting reduction in return of blood to the heart. Because cardiac output is directly related to cardiac preload (Starling's law of the heart) (27), cardiac output tends to decrease during head-up movements (25). Furthermore, cardiac output and peripheral vascular resistance determine systemic blood pressure, such that the sympathetic nervous system must produce a rapid net increase in peripheral resistance by inducing vasoconstriction at the onset of head-up body rotations to maintain stable blood pressure (7). Arterial baroreceptor mechanisms play an important role in regulating peripheral vasoconstriction during postural alterations (23). In addition, there is considerable evidence from studies in animals (6,8,10,11,21,22,32) and humans (1,4,12,23,26,28,30) that the vestibular system also participates in triggering increases in vasomotor activity during movements that promote peripheral blood pooling...

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Section: Methodsmentioning

confidence: 99%

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Yavorcik¹,

Reighard²,

Misra³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In contrast, forelimb vascular resistance was similar during head-up movements before and after the removal of labyrinthine inputs, indicating that the vestibular system has distinct influences on lower and upper body vasculature (307). Furthermore, removal of vestibular inputs resulted in an increase in baseline blood flow to the head measured when the animals were prone (306), but no changes in baseline blood flow to the forelimb or hindlimb (307, 331). These observations, in combination with data from experiments using electrical stimulation of vestibular afferents, solidly demonstrate that VSR are anatomically patterned.…”

Section: Patterning Of Vestibulosympathetic Reflexesmentioning

confidence: 98%

“…The effects of removal of labyrinthine inputs on carotid artery blood flow to the head have also been assessed in conscious animals (306). Unlike limb blood flow, blood flow to the head measured when animals were in the prone position increased appreciably after bilateral transection of the VIII th nerves.…”

Section: Characteristics Of Vestibulo-sympathetic Reflexes In Animal mentioning

confidence: 99%

“…Studies assessing the effects of removal of vestibular inputs on the regulation of blood pressure and peripheral blood flow showed that impairments in the cardiovascular responses dissipated over time (306, 307, 331). It thus appears that alternate mechanisms can at least partially replace VSR.…”

Section: Recovery Of Posturally-related Cardiovascular Responses Follmentioning

confidence: 99%

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Vestibulo‐Sympathetic Responses

Yates

Bolton

Macefield

2014

Comprehensive Physiology

141

130

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Evidence accumulated over 30 years, from experiments on animals and human subjects, has conclusively demonstrated that inputs from the vestibular otolith organs contribute to the control of blood pressure during movement and changes in posture. This review considers the effects of gravity on the body axis, and the consequences of postural changes on blood distribution in the body. It then separately considers findings collected in experiments on animals and human subjects demonstrating that the vestibular system regulates blood distribution in the body during movement. Vestibulosympathetic reflexes differ from responses triggered by unloading of cardiovascular receptors such as baroreceptors and cardiopulmonary receptors, as they can be elicited before a change in blood distribution occurs in the body. Dissimilarities in the expression of vestibulosympathetic reflexes in humans and animals are also described. In particular, there is evidence from experiments in animals, but not humans, that vestibulosympathetic reflexes are patterned, and differ between body regions. Results from neurophysiological and neuroanatomical studies in animals are discussed that identify the neurons that mediate vestibulosympathetic responses, which include cells in the caudal aspect of the vestibular nucleus complex, interneurons in the lateral medullary reticular formation, and bulbospinal neurons in the rostral ventrolateral medulla (RVLM). Recent findings showing that cognition can modify the gain of vestibulosympathetic responses are also presented, and neural pathways that could mediate adaptive plasticity in the responses are proposed, including connections of the posterior cerebellar vermis with the vestibular nuclei and brainstem nuclei that regulate blood pressure.

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“…Bilateral vestibular nerve lesions raise the probability of orthostatic intolerance in awake animals as well [1,32,58,78] (for review, see [133]), although cerebral blood flow is not compromised [122]. The generality of this finding was extended in studies showing that otolith-specific stimulation achieved through linear acceleration [2] or head-up tilt increased sympathetic nerve activity [131] and elevated blood pressure [123], while nose-down stimulation decreased this activity [78], as is observed in humans.…”

Section: The Role Of Primary Vestibular Afferents In the Sympathetmentioning

confidence: 99%

Anatomical observations of the caudal vestibulo-sympathetic pathway

Martinelli

Friedrich

2011

VES

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The vestibular system senses the movement and position of the head in space and uses this information to stabilize vision, control posture, perceive head orientation and self-motion in three-dimensional space, and modulate autonomic and limbic activity in response to locomotion and changes in posture. Most vestibular signals are not consciously perceived and are usually appreciated through effector pathways classically described as the vestibulo-ocular, vestibulo-spinal, vestibulo-collic and vestibulo-autonomic reflexes. The present study reviews some of the recent data concerning the connectivity and chemical anatomy of vestibular projections to autonomic sites that are important in the sympathetic control of blood pressure.

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Effects of postural changes and removal of vestibular inputs on blood flow to the head of conscious felines

Cited by 24 publications

References 22 publications

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Effects of postural changes and removal of vestibular inputs on blood flow to and from the hindlimb of conscious felines

Vestibulo‐Sympathetic Responses

Anatomical observations of the caudal vestibulo-sympathetic pathway

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