El-Mas M M, Abdel-Rahman A A
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC 27858, USA.
Eur J Pharmacol. 1998 May 22;349(2-3):253-61. doi: 10.1016/s0014-2999(98)00202-7.
Our previous studies have shown that ethanol attenuates baroreflex control of heart rate in male rats. The present study investigated whether this effect of ethanol is gender-related, and whether it involves hormonal factors. The effect of intragastric administration of ethanol or equal volume of water on baroreflex-mediated decreases in heart rate in response to increments in blood pressure evoked by phenylephrine were evaluated in conscious age-matched male and female Sprague-Dawley rats as well as in ovariectomized rats. Baroreflex curves relating changes in blood pressure and associated heart rate responses were constructed, and the slopes of the regression lines were taken as a measure of baroreflex sensitivity. Phenylephrine (1-16 microg kg(-1), i.v.) elicited dose-dependent pressor responses that were similar in all groups of rats. However, the associated reflex bradycardic responses depended on the rat preparation and the dose of ethanol employed. In water-treated (control) animals, significantly (P < 0.05) lesser reflex bradycardic responses were observed in female compared with male rats (baroreflex sensitivity, -1.21 +/- 0.12 vs. -1.67 +/- 0.12 beats min(-1) mmHg(-1)). Ovariectomy resulted in a further reduction in baroreflex sensitivity (-0.82 +/- 0.06 beats min(-1) mmHg(-1)), suggesting a favorable role for ovarian hormones in baroreflex modulation. In male rats, ethanol (0.25, 0.5, or 1 g kg(-1), intragastric) elicited dose-related decreases in reflex bradycardic responses. The reduction in the regression coefficient obtained by the two higher doses (0.5 and 1 g kg(-1)) of ethanol was statistically significant compared with control values. The ability of ethanol to reduce baroreflex sensitivity appears to be gender-independent as it was similarly demonstrated in intact female rats. In contrast, ethanol had no effect on reflex bradycardic responses in ovariectomized rats at any of the doses tested. The data suggest that ethanol reduces baroreflex control of heart rate irrespective of the rat gender. Further, the lack of an effect of ethanol on baroreflex sensitivity in ovariectomized rats may suggest a role for ovarian hormones in ethanol-evoked baroreflex attenuation.
我们之前的研究表明，乙醇会减弱雄性大鼠心率的压力反射控制。本研究调查了乙醇的这种作用是否与性别相关，以及是否涉及激素因素。在年龄匹配的清醒雄性和雌性Sprague-Dawley大鼠以及去卵巢大鼠中，评估了胃内给予乙醇或等量水对苯肾上腺素诱发血压升高时压力反射介导的心率降低的影响。构建了与血压变化和相关心率反应相关的压力反射曲线，并将回归线的斜率作为压力反射敏感性的指标。苯肾上腺素（1 - 16微克/千克，静脉注射）在所有大鼠组中均引起剂量依赖性升压反应。然而，相关的反射性心动过缓反应取决于大鼠的制备情况和所用乙醇的剂量。在给予水处理（对照）的动物中，与雄性大鼠相比，雌性大鼠的反射性心动过缓反应明显较小（P < 0.05）（压力反射敏感性，-1.21 ± 0.12对-1.67 ± 0.12次/分钟·毫米汞柱⁻¹）。去卵巢导致压力反射敏感性进一步降低（-0.82 ± 0.06次/分钟·毫米汞柱⁻¹），表明卵巢激素在压力反射调节中起有利作用。在雄性大鼠中，乙醇（0.25、0.5或1克/千克，胃内给药）引起反射性心动过缓反应的剂量相关降低。与对照值相比，乙醇的两个较高剂量（0.5和1克/千克）所获得的回归系数降低具有统计学意义。乙醇降低压力反射敏感性的能力似乎与性别无关，因为在完整雌性大鼠中也有类似表现。相反，在所测试的任何剂量下，乙醇对去卵巢大鼠的反射性心动过缓反应均无影响。数据表明，乙醇会降低心率的压力反射控制，而与大鼠性别无关。此外，乙醇对去卵巢大鼠压力反射敏感性无影响可能表明卵巢激素在乙醇诱发的压力反射减弱中起作用。
