Effects of pregnancy and progesterone metabolites on arterial baroreflex in conscious rats.
Effects of pregnancy and progesterone metabolites on arterial baroreflex in conscious rats.
复制标题
妊娠和孕酮代谢物对清醒大鼠动脉压力反射的影响。
DOI：
10.1152/ajpregu.1997.272.3.r924
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Heesch,CM
中科院分区：
文献类型：
--
作者：
Masilamani,S;Heesch,CM
先前在麻醉大鼠中的实验表明，妊娠（P）大鼠的交感兴奋反应减弱。孕激素的主要代谢物3 α-羟基-二氢孕酮（3 α-OH-DHP）在妊娠期升高，据报道可增强中枢γ-氨基丁酸能机制，而3 β-异构体（3 β-OH-DHP）无活性。本研究通过记录P大鼠和未孕大鼠在输注苯肾上腺素（PE）和硝普钠（NTP）前（对照组）和输注后15分钟（i. v.）或3beta-OH-DHP。P大鼠的基线MAP较低（P = 102 +/- 2 vs. V = 124 +/- 3 mmHg）。与V大鼠相比，P大鼠表现出较少的“交感神经储备”，以响应一个膨胀的挑战，证明了减少最大NA和RSNA压力感受性反射反应的斜率降低NTP。然而，HR压力感受性反射曲线在P和V大鼠中相似。对清醒的V大鼠急性静脉注射3 α-OH-DHP模拟了妊娠的影响。压力反射交感兴奋性反应减少，而HR的压力反射控制不受影响。DHP的3 β-异构体对NA或HR压力感受性反射反应没有影响。这些结果表明，怀孕可能有不同的影响压力反射控制交感神经流出和HR，和孕激素的主要代谢产物，3 α-OH-DHP，可能有助于这种适应怀孕。
Previous experiments in anesthetized rats suggested that sympathoexcitatory responses were attenuated in pregnant (P) rats. The major progesterone metabolite, 3alpha-hydroxy-dihydroprogesterone (3alpha-OH-DHP), is elevated in pregnancy and reportedly potentiates central gamma-aminobutyric acidergic mechanisms, whereas the 3beta-isomer (3beta-OH-DHP) is inactive. This study obtained baroreflex curves in conscious rats by recording reflex changes in renal sympathetic nerve activity (RSNA) and heart rate (HR) due to perturbations in mean arterial pressure (MAP) [i.v. phenylephrine (PE) and nitroprusside (NTP)] in P rats and in virgin (V) rats before (control) and 15 min after infusion (i.v.) of 3alpha-OH-DHP or 3beta-OH-DHP. Baseline MAP was lower in P rats (P = 102 +/- 2 vs. V = 124 +/- 3 mmHg). Compared with V rats, P rats exhibited less "sympathetic reserve" to respond to a hypotensive challenge, as evidenced by decreased maximum NA and decreased slope of RSNA baroreflex responses to NTP. However, HR baroreflex curves were similar in P and V rats. Acute intravenous administration of 3alpha-OH-DHP to conscious V rats mimicked the effects of pregnancy. Baroreflex sympathoexcitatory responses were decreased, whereas baroreflex control of HR was unaffected. The 3beta-isomer of DHP had no effect on NA or HR baroreflex responses. These results suggest that pregnancy may have differential effects on baroreflex control of sympathetic outflow and HR, and the major metabolite of progesterone, 3alpha-OH-DHP, may contribute to this adaptation of pregnancy.