IngentaConnect Orthostatic Response in Rats After Hindlimb Unloading: Effect of ...

Authors: Tarasova, Olga¹; Borovik, Anatoly¹; Tsvirkoun, Daria¹; Lebedev, Valery¹; Steeves, John¹; Krassioukov, Andrei¹

Source: Aviation, Space, and Environmental Medicine, Volume 78, Number 11, November , 2007 , pp. 1023-1028(6)

Publisher: Aerospace Medical Association

Abstract:

Tarasova O, Borovik A, Tsvirkoun D, Lebedev V, Steeves J, Krassioukov A. Orthostatic response in rats after hindlimb unloading: effect of transcranial electrical stimulation. Aviat Space Environ Med 2007; 78:1023-8.

Introduction: Orthostatic hypotension is a commonly observed phenomenon after exposure to microgravity and in various forms of autonomic failure. It has been suggested that insufficient activation of supraspinal structures responsible for descending sympathetic drive could play a significant role in this disorder. We examined the effect of transcranial electrical stimulation (TES) of autonomic nuclei within the brain on the orthostatic hypotension induced by exposure to simulated microgravity using a hindlimb unloading model. Methods: There were 20 male Wistar rats that were suspended by their tail with the angle of elevation between the cage floor and the rat's body approximately 40°. There were 11 age-matched Wistar rats used as cage controls. Orthostatic stability was examined by using an orthostatic challenge test (45° head-up test for a period of 3 min). In 10 rats from the tail-suspended group, the orthostatic challenge test was applied during TES. Results: In the rats exposed to simulated microgravity (tail suspension), the orthostatic challenge test caused a significant decrease in mean arterial blood pressure by 18.4 ± 2.2%. TES attenuated this microgravity-induced orthostatic hypotension to 9.5 ± 1.8% (P < 0.05), which was similar to the observed response to an orthostatic challenge in the control group (6.9 ± 1.1%). Discussion: Results of this study suggest that TES significantly reduces the changes in blood pressure during an orthostatic challenge test in animals exposed to simulated microgravity. Our observations support the notion that a reduction in descending sympathoexcitatory input from supraspinal structures could contribute to orthostatic hypotension and intolerance observed in astronauts following their return from spaceflight.

Keywords: blood pressure; orthostatic hypotension; tilt test; microgravity

Document Type: Research article

DOI: 10.3357/ASEM.2062.2007

Affiliations: 1: From the State Research Center of the Russian Federation, Institute for Biomedical Problems, Moscow, Russia (O. Tarasova, A. Borovik, D. Tsvirkoun); the Department of Human & Animal Physiology, M.V. Lomonosov Moscow State University, Moscow, Russia (O. Tarasova, D. Tsvirkoun), the I.P. Pavlov Institute of Physiology, St. Petersburg, Russia (V. Lebedev); International Collaboration On Repair Discovery (ICORD), University of British Columbia, Vancouver, BC, Canada (J. Steeves, A. Krassioukov); and the Division of Physical Medicine and Rehabilitation, Department of Medicine, University of British Columbia and Vancouver Coastal Health, Vancouver, BC, Canada (A. Krassioukov).

Orthostatic Response in Rats After Hindlimb Unloading: Effect of Transcranial Electrical Stimulation