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Increased GABA(A) inhibition of the RVLM after hindlimb unloading in ratsAttenuated baroreflex-mediated increases in renal sympathetic nerve activity (RSNA) in hindlimb unloaded (HU) rats apparently are due to changes within the central nervous system. We hypothesized that GABA(A) receptor-mediated inhibition of the rostral ventrolateral medulla (RVLM) is increased after hindlimb unloading. Responses to bilateral microinjection of the GABA(A) antagonist (-)-bicuculline methiodide (BIC) into the RVLM were examined before and during caudal ventrolateral medulla (CVLM) inhibition in Inactin-anesthetized control and HU rats. Increases in mean arterial pressure (MAP), heart rate (HR), and RSNA in response to BIC in the RVLM were significantly enhanced in HU rats. Responses to bilateral CVLM blockade were not different. When remaining GABA(A) inhibition in the RVLM was blocked by BIC during CVLM inhibition, the additional increases in MAP and RSNA were significantly greater in HU rats. These data indicate that GABA(A) receptor-mediated inhibition of RVLM neurons is augmented after hindlimb unloading. Effects of input from the CVLM were unaltered. Thus, after cardiovascular deconditioning in rodents, the attenuated increase in sympathetic nerve activity in response to hypotension is associated with greater GABA(A) receptor-mediated inhibition of RVLM neurons originating at least in part from sources other than the CVLM.
Document ID
20040088172
Document Type
Reprint (Version printed in journal)
Authors
Moffitt, Julia A. (Dalton Cardiovascular Research Center, University of Missouri Columbia, Missouri 65211, United States)
Heesch, Cheryl M.
Hasser, Eileen M.
Date Acquired
August 21, 2013
Publication Date
September 1, 2002
Publication Information
Publication: American journal of physiology. Regulatory, integrative and comparative physiology
Volume: 283
Issue: 3
ISSN: 0363-6119
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: HL-36245
CONTRACT_GRANT: HL-55306
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Cardiopulmonary