Baroreceptor reflex functioning is under the influence of several factors including steroid hormones. In pregnancy, there is an attenuation of the baroreceptor reflex such that in late pregnancy, animals are unable to maintain pressure during hemorrhage. Since hemorrhage is a common occurrence in labor and delivery, the importance of understanding this observation is noteworthy. The hypothesis to be tested in the current proposal is that this deficit occurs in the brain or efferent part of the reflex pathway whereas the afferent pathway is not altered. Conscious rabbits will be studied to determine if sympathetic activity is less in pregnant animals during hemorrhage. Assessments of sympathetic activity include, renal nerve recordings and regional resistances, plasma catecholamines, total and renal norepinephrine spillover, and adrenal and ganglionic levels of tyrosine hydroxylase mRNA. Responsiveness of single arterial baroreceptor fibers and efferent responses to stimulation of the aortic depressor nerve will be determined. Vasodilator responses of isolated resistance vessels will also be assessed. The timing of the above changes during pregnancy and lactation will be studied.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL039923-06
Application #
2519300
Study Section
Experimental Cardiovascular Sciences Study Section (ECS)
Project Start
1988-08-01
Project End
2000-08-31
Budget Start
1997-09-01
Budget End
1998-08-31
Support Year
6
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Oregon Health and Science University
Department
Physiology
Type
Schools of Medicine
DUNS #
009584210
City
Portland
State
OR
Country
United States
Zip Code
97239
Anglin, Joy C; Brooks, Virginia L (2003) Tyrosine hydroxylase and norepinephrine transporter in sympathetic ganglia of female rats vary with reproductive state. Auton Neurosci 105:8-15
Clow, Kathy A; Giraud, George D; Ogden, Bryan E et al. (2003) Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits. Am J Physiol Heart Circ Physiol 284:H1110-8
Brooks, Virginia L; Clow, Kathy A; O'Hagan, Kathleen P (2002) Pregnancy and acute baroreflex resetting in conscious rabbits. Am J Physiol Regul Integr Comp Physiol 283:R429-40
Brooks, V L; Clow, K A; Welch, L S et al. (2001) Does nitric oxide contribute to the basal vasodilation of pregnancy in conscious rabbits? Am J Physiol Regul Integr Comp Physiol 281:R1624-32
Brooks, V L; Kane, C M; Welch, L S (1999) Regional conductance changes during hemorrhage in pregnant and nonpregnant conscious rabbits. Am J Physiol 277:R675-81
Brooks, V L; Quesnell, R R; Kane, C M et al. (1998) Hemodynamic and hormonal responses to hemorrhage in conscious rabbits at mid- and late gestation. Am J Physiol 275:R1082-90
Quesnell, R R; Brooks, V L (1997) Alterations in the baroreflex occur late in pregnancy in conscious rabbits. Am J Obstet Gynecol 176:692-4
Brooks, V L; Kane, C M; Van Winkle, D M (1997) Altered heart rate baroreflex during pregnancy: role of sympathetic and parasympathetic nervous systems. Am J Physiol 273:R960-6
Brooks, V L; Quesnell, R R; Cumbee, S R et al. (1995) Pregnancy attenuates activity of the baroreceptor reflex. Clin Exp Pharmacol Physiol 22:152-6
Brooks, V L; Keil, L C (1994) Hemorrhage decreases arterial pressure sooner in pregnant compared with nonpregnant dogs: role of baroreflex. Am J Physiol 266:H1610-9

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