Tanabe S, Buñag R D
Department of Pharmacology, College of Health Sciences and Hospital, University of Kansas Medical Center, Kansas City 66103.
Am J Physiol. 1989 May;256(5 Pt 2):H1399-406. doi: 10.1152/ajpheart.1989.256.5.H1399.
To determine whether baroreflex sensitivity changes with age, we compared drug-induced reflex responses in 2- and 9-mo-old female Sprague-Dawley rats anesthetized with urethan-chloralose. Baroreflexes were stimulated by elevating or lowering blood pressure with intravenous infusions of phenylephrine or sodium nitroprusside. Reflex responses in heart rate and sympathetic nerve activity during phenylephrine infusions were weaker in 9- than in 2-mo-old rats, as were reflex tachycardia during sodium nitroprusside infusion and decreases in heart rate and sympathetic nerve activity elicited by electrical stimulation of the left aortic depressor nerve. Afferent aortic nerve activity was also appreciably lower in 9-mo-old rats at pressures greater than 130 mmHg but did not differ between rat groups at normotensive pressures. These results suggest that baroreflex sensitivity in 9-mo-old rats can be characterized as follows: 1) impaired at pressures greater than 130 mmHg but still adequate at normotensive pressures, and 2) all reflex arc components may be impaired.
为了确定压力感受性反射敏感性是否随年龄变化，我们比较了用乌拉坦-氯醛糖麻醉的2月龄和9月龄雌性斯普拉格-道利大鼠的药物诱导反射反应。通过静脉输注去氧肾上腺素或硝普钠升高或降低血压来刺激压力感受性反射。在输注去氧肾上腺素期间，9月龄大鼠心率和交感神经活动的反射反应比2月龄大鼠弱，硝普钠输注期间的反射性心动过速以及电刺激左主动脉减压神经引起的心率和交感神经活动降低也是如此。在血压高于130 mmHg时，9月龄大鼠的主动脉传入神经活动也明显较低，但在正常血压时两组大鼠之间没有差异。这些结果表明，9月龄大鼠的压力感受性反射敏感性可表现为：1）在血压高于130 mmHg时受损，但在正常血压时仍足够；2）所有反射弧成分可能均受损。
