Pregnancy and acute baroreflex resetting in conscious rabbits.
Pregnancy and acute baroreflex resetting in conscious rabbits.
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DOI：
10.1152/ajpregu.00014.2002
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发表时间：
2002-08
期刊：
影响因子：
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通讯作者：
V. Brooks;K. Clow;K. O’Hagan
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文献类型：
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作者：
V. Brooks;K. Clow;K. O’Hagan
为了验证心率（HR）的急性重置控制在怀孕期间得到加强的假设，我们确定了在动脉压升高[~25 mmHg，输注苯肾上腺素（PE）或甲氧苄胺（Meth） 30分钟]后，与未怀孕的意识兔相比，妊娠后期动脉压与HR之间的血压反射关系的右移是否更大。通过监测HR对动脉压逐步稳态变化（n = 14）和快速斜坡变化（n = 10）的反应来评估压力反射功能。无论采用稳态法还是斜坡法，妊娠均降低了反射增益，增加了反射最小HR，并使曲线向更低的压力水平移动（均P < 0.05）。在妊娠前期和妊娠期间，均可观察到PE加压时稳态曲线的复位，但在妊娠兔中复位的幅度较小。对数据的进一步检查显示，怀孕家兔的位移大小与PE剂量呈负相关。因为在所有的实验中血压升高是相同的，PE似乎非特异性地抵消了急性重置。当使用甲基苯丙胺来增加压力时，在怀孕和未怀孕的兔子中，稳态曲线的重置是相似的，与剂量无关。同样，当使用斜坡法生成反射曲线时，使用甲基安非他明或低剂量PE来增加压力，在怀孕和未怀孕的家兔之间没有观察到重置程度的差异。综上所述，高剂量的PE可抵消HR压力反射控制的急性重置。更重要的是，虽然压力反射功能受到抑制，但压力反射的重置能力似乎在怀孕期间得到了保留。
To test the hypothesis that acute resetting of baroreflex control of heart rate (HR) is enhanced during pregnancy, we determined whether the rightward shift in the baroreflex relationship between arterial pressure and HR after arterial pressure is raised [~25 mmHg for 30 min, due to infusion of phenylephrine (PE) or methoxamine (Meth)] is greater in late pregnant compared with nonpregnant conscious rabbits. Baroreflex function was assessed by monitoring HR responses to both stepwise steady-state changes (n = 14) and rapid ramp changes (n = 10) in arterial pressure. Pregnancy decreased reflex gain, increased reflex minimum HR, and shifted the curves to a lower pressure level, when either the steady-state or ramp method was used (all changes, P < 0.05). When PE was used to increase pressure, resetting of steady-state curves was observed both before and during pregnancy, but the magnitude of the resetting was less in the pregnant rabbits. Further inspection of the data revealed that the size of the shift in pregnant rabbits was inversely related to the dose of PE. Because the pressure rise was the same in all experiments, PE appears to nonspecifically counteract acute resetting. When Meth was used instead to increase pressure, resetting of steady-state curves was similar in pregnant and nonpregnant rabbits and was unrelated to dose. Similarly, when reflex curves were generated using the ramp method, and either Meth or low doses of PE were used to increase pressure, no differences in the degree of resetting were observed between pregnant and nonpregnant rabbits. In summary, high doses of PE counteract acute resetting of baroreflex control of HR. More importantly, while baroreflex function is depressed, the ability of the baroreflex to reset appears to be preserved during pregnancy.