What is the clinical evidence from this study?

Study design: Other. Population: Pregnancy. Intervention: Pregnancy vs. Virgin rats. Primary outcome: Aortic depressor nerve activity (ADNA) in response to pressure stimulus (p=<0.05).

June 1, 2000

Baroreceptor afferent discharge in the pregnant rat

Q: What are the key findings of this study?

Pregnancy in rats significantly attenuated aortic depressor nerve activity during both phenylephrine and sodium nitroprusside infusions (P<0.05) due to a more rapid adaptation to pressure stimuli.

Key Result

Pregnancy in rats significantly attenuated aortic depressor nerve activity during both phenylephrine and sodium nitroprusside infusions (P<0.05) due to a more rapid adaptation to pressure stimuli.

Structured PICO

Does pregnancy attenuate arterial baroreceptor afferent discharge in response to pressure stimuli in rats?

Population

Anesthetized late-pregnant and virgin rats evaluated for baroreceptor afferent discharge in response to pressure stimuli.

Exposure

Increases in mean arterial pressure via phenylephrine (PE) and decreases via sodium nitroprusside (SNP)

Comparator

Virgin rats

Outcome

Multifiber aortic depressor nerve activity (ADNA), mean arterial pressure (MAP), and heart ratesurrogate

Pregnancy attenuates baroreceptor afferent discharge in rats due to a more rapid adaptation to pressure stimuli.

Main Result

p-value: p=<0.05

Abstract

Pregnancy is associated with blunted reflex responses to cardiac and arterial baroreceptor stimulation. We tested the hypothesis that arterial baroreceptor afferent discharge is attenuated in response to a pressure stimulus in pregnant rats. Multifiber aortic depressor nerve activity (ADNA), mean arterial pressure (MAP), and heart rate were measured in anesthetized (pentobarbital sodium, 35 mg/kg ip) late-pregnant and virgin rats in response to increases ¿phenylephrine (PE), 1.5-24 microg. kg(-1). min(-1) and 1-16 microg/kg and decreases ¿sodium nitroprusside (SNP), 5-80 microg. kg(-1). min(-1) and 0.05-16 microg/kg in MAP. Resting MAP was lower in pregnant rats, but changes in MAP were similar to those in virgin rats during both PE and SNP administration. ADNA was significantly attenuated in pregnant animals during both PE and SNP infusions (P < 0.05) due to a more rapid adaptation to the pressure stimulus. Bolus drug administration evoked similar changes in MAP and ADNA in both groups; however, the maximum decrease in ADNA was achieved at the lowest dose of SNP in pregnant rats. Thus baroreceptor afferent discharge is attenuated in pregnant rats, and this involves a more rapid adaptation to a pressure stimulus.

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