Pregnancy in rats resulted in a lower baseline MAP (96 vs 113 mmHg) and a leftward shift of the baroreflex function curve, with impaired sympathetic response to hypotension.
Does pregnancy alter baroreflex control of sympathetic outflow and the response to captopril in rats?
Pregnancy in rats shifts the baroreflex function curve to a lower operating pressure range and impairs the sympathetic response to hypotension, independent of angiotensin-converting enzyme activity.
Tasa de eventos absoluta: 96% vs 113%
Arterial baroreflex control of renal sympathetic nerve activity (RSNA) was compared in nonpregnant (NP) and near-term pregnant (P) chloralose-anesthetized rats. Baroreflex curves were obtained by recording reflex changes in RSNA (expressed as a percent of base line) due to increases and decreases in mean arterial pressure (MAP) intravenous phenylephrine and nitroprusside (NTP). The slope, midpoint (EP50), and threshold pressures of the baroreflex curves were compared. Base-line MAP was significantly lower in the pregnant animals (P = 96 +/- 3 vs. NP = 113 +/- 5 mmHg). The baroreflex curves of pregnant animals also had significantly lower threshold (P = 95 +/- 3 vs. NP = 110 +/- 5 mmHg) and midpoint values (P = 105 +/- 4 vs. NP = 119 +/- 5 mmHg). The response to unloading the baroreceptors was attenuated in the pregnant animals as indicated by a decrease in slope of the NTP portion of the baroreflex curve (P = 0.95 +/- 0.17 vs. NP = 1.61 +/- 0.29% nerve activity/mmHg). Responses to blockade of angiotensin-converting enzyme with captopril (2 mg/kg iv) were also examined. There were no differences in EP50 or slope among the control, captopril, and recovery baroreflex curves within either the nonpregnant or pregnant animals. However, after captopril, MAP decreased to a greater extent in the pregnant rats, yet RSNA increased to the same level for the two groups. Thus pregnancy results in a leftward shift of the baroreflex function curve toward a lower operating pressure range. In addition, pregnant rats demonstrated an impaired ability to increase sympathetic outflow above base-line values in response to a hypotensive challenge.
Crandall et al. (Fri,) conducted a other in Pregnancy. Pregnancy vs. Nonpregnant rats was evaluated on Base-line mean arterial pressure (MAP). Pregnancy in rats resulted in a lower baseline MAP (96 vs 113 mmHg) and a leftward shift of the baroreflex function curve, with impaired sympathetic response to hypotension.
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