Document Detail

CNS effects of ovarian hormones and metabolites on neural control of circulation.
MedLine Citation:
PMID:  11458692     Owner:  NLM     Status:  MEDLINE    
Pregnant women often experience orthostatic hypotension, and pregnancy is associated with increased susceptibility to hemorrhagic hypotension. Experiments evaluating arterial baroreflex control of efferent sympathetic nerve activity in virgin and term-pregnant rats revealed that arterial baroreflex sympathoexcitation is attenuated, while sympathoinhibitory responses are well-maintained or potentiated. Following a hypotensive challenge, pregnant animals exhibit attenuated Fos expression in the rostral ventrolateral medulla (RVLM), suggesting that unloading of arterial baroreceptors results in less excitation of presympathetic neurons in the brain stem. Other experiments, in which afferent baroreceptor discharge was recorded, suggest that this was not due to differences in afferent baoreceptor function. GABAergic mechanisms are responsible for tonic inhibition of sympathoexcitatory neurons in the RVLM and the major metabolite of progesterone, 3 alpha-OH-dihydro-progesterone (3 alpha-OH-DHP), which is elevated in pregnancy, is the most potent endogenous positive modulator of CNS GABAA receptor function. Additional experiments revealed that acutely administered 3 alpha-OH-DHP, either intravenously or directly into the RVLM, mimicked the effects of pregnancy on baroreflex control of efferent sympathetic nerve activity and potentiated pressure sensitivity of spinally projecting RVLM neurons. Preliminary experiments using semiquantitative RT-PCR, evaluated the relative expression of three subunits (alpha 1-3) of the GABAA receptor, and suggest that chronic exposure to elevated levels of ovarian hormones can result to changes in GABAA receptor subunit composition. It is likely that changes in control of sympathetic outflow in pregnancy are related to complex interactions between genomic and nongenomic actions of ovarian hormones and metabolites.
C M Heesch; C M Foley
Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Annals of the New York Academy of Sciences     Volume:  940     ISSN:  0077-8923     ISO Abbreviation:  Ann. N. Y. Acad. Sci.     Publication Date:  2001 Jun 
Date Detail:
Created Date:  2001-07-18     Completed Date:  2001-08-09     Revised Date:  2005-11-16    
Medline Journal Info:
Nlm Unique ID:  7506858     Medline TA:  Ann N Y Acad Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  348-60     Citation Subset:  IM    
Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Research Park, Columbia, MO 65211-3300, USA.
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MeSH Terms
Baroreflex / physiology
Blood Circulation / physiology*
Brain Stem / metabolism
Central Nervous System / physiology*
Hormones / physiology*
Ovary / metabolism*
Progesterone / metabolism
Proto-Oncogene Proteins c-fos / metabolism
Receptors, GABA-A / physiology
Reg. No./Substance:
0/Hormones; 0/Proto-Oncogene Proteins c-fos; 0/Receptors, GABA-A; 57-83-0/Progesterone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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