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The Hypo-Osmolality of Pregnancy Does Not Alter Baroreceptor Responses to Acute Changes in Osmolality

University of Missouri, Kansas City School of Nursing, Kansas City, MO, hinesmc{at}umkc.edu

Jessica Veeh, BS

University of Missouri, Kansas City School of Nursing, Kansas City, MO

Dawn Grimes, BSN

University of Missouri, Kansas City School of Nursing, Kansas City, MO

Reducing extracellular osmolality by 10-12 mOsm/L reduces baroreceptor firing in vitro in tissues from male rats. Pregnancy is associated with a similar reduction in plasma osmolality (pOsm) as well as with alterations in baroreceptor firing and reduced baroreceptor reflex activity. Mechanisms for reduced baroreflex activity are not yet understood, but they have important implications for maintenance of cardiovascular homeostasis in the pregnant female. Thus, this study was designed to test whether changes in plasma osmolality alter baroreceptor discharge during pregnancy. Late-gestation pregnant and virgin control rats were anesthetized, femoral vessels were cannulated for measurement of arterial pressure and drug infusion, and the aortic depressor nerve, containing baroreceptor afferents, was isolated and prepared for recording. Plasma osmolality was measured before and 30 min after graded intraperitoneal injections of NaCl (50-1500 mOsm/L). Arterial pressure, heart rate, and aortic depressor nerve activity (ADNA) were measured continuously before and after injections. A 50 mOsm/L NaCl injection significantly decreased pOsm but did not alter ADNA in either group. Likewise, 1200 mOsm/L NaCl injections significantly increased pOsm and had no effect on ADNA in either group. The 1500 mOsm salt load significantly increased pOsm and ADNA in pregnant rats, and in virgin animals, it increased pOsm but evoked a paradoxical decrease in ADNA. The authors’ studies indicate that pOsm has minimal effects on baroreceptor activity, which are not significantly different during gestation. Their findings suggest that in vitro data from male rats indicating a correlation between pOsm and baroreceptor discharge are not applicable in anesthetized intact female animals.

Key Words: sodium chloride • pregnancy • aortic depressor nerve • baroreceptor • osmolality

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Biological Research For Nursing, Vol. 7, No. 3, 214-221 (2006)
DOI: 10.1177/1099800405283032


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This Article Abstract Free Full Text (Free PDF) Free Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Hines, T. Articles by Grimes, D. Search for Related Content PubMed PubMed Citation Articles by Hines, T. Articles by Grimes, D. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Medline Plus Health Information High Risk Pregnancy Hazardous Substances DB SODIUM CHLORIDE Social Bookmarking                         What's this?