AUGMENTATION OF BAROREFLEX-MEDIATED BRADYCARDIA IN CONSCIOUS PREGNANT RATS

被引:33
作者
CONRAD, KP [1 ]
RUSS, RD [1 ]
机构
[1] UNIV NEW MEXICO,SCH MED,DEPT OBSTET & GYNECOL,ALBUQUERQUE,NM 87131
来源
AMERICAN JOURNAL OF PHYSIOLOGY | 1992年 / 262卷 / 03期
关键词
SYSTEMIC PRESSOR AND DEPRESSOR RESPONSE; RESTING MEAN ARTERIAL PRESSURE AND HEART RATE; METHOXAMINE; SODIUM NITROPRUSSIDE; CHRONICALLY INSTRUMENTED UNRESTRAINED RAT;
D O I
10.1152/ajpregu.1992.262.3.R472
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
The goal of the present study was to examine baroreflex control of heart rate during pregnancy in chronically instrumented unrestrained rats. The same rats (n = 6) were studied before conception, again on gestational days 5, 12, and 19, and last on postpartum day 6; thus each rat served as its own control. Time control experiments were also conducted in a separate group of virgin rats (n = 7). Resting mean arterial pressure decreased by 10 mmHg on gestational day 19 (P < 0.01 vs. prepregnant), and heart rate significantly increased by approximately 10% relative to time control rats. Dose-response curves were constructed for methoxamine and sodium nitroprusside comparing the various dosages with systemic pressor and depressor responses, respectively. The dose-response relationship for methoxamine was shifted to the right in gravid rats of 19 gestational days (P < 0.03 vs. prepregnant), indicating an attenuation of alpha-adrenergic receptor-mediated pressor responsiveness. In contrast, depressor responses to sodium nitroprusside were not significantly altered in pregnancy. Baroreflex-mediated bradycardia was unchanged until gestational day 19, when enhanced bradycardic responses to methoxamine were observed. Baroreflex-mediated tachycardic responses elicited by sodium nitroprusside were not affected at any stage of pregnancy. Baroreflex control of heart rate did not change significantly with either increases or decreases of blood pressure in time control experiments. We conclude that during late pregnancy in conscious rats 1) resting blood pressure decreases and heart rate increases, 2) systemic pressor responses to methoxamine are diminished, and 3) baroreflex-mediated bradycardia is enhanced.
引用
收藏
页码:R472 / R477
页数:6
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