Nedvídek J, Zicha J
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
Physiol Res. 2000;49(3):323-30.
Baroreflex control of heart rate was studied in inbred salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) Dahl rats that were subjected to chronic dietary sodium chloride loading (for 4 weeks) either in youth or only in adulthood, i.e. from the age of 4 or 12 weeks. Using phenylephrine administration to pentobarbital-anesthetized male rats we have demonstrated the decreased baroreflex sensitivity (lower slope for reflex bradycardia) in young prehypertensive SS/Jr rats fed a low-salt diet as compared to age-matched SR/Jr animals. High salt intake further suppressed baroreflex sensitivity in young SS/Jr but not in SR/Jr rats. Baroreflex sensitivity decreased with age in SR/Jr rats, whereas it increased in SS/Jr rats fed a low-salt diet. Thus at the age of 16 weeks baroreflex sensitivity was much higher in SS/Jr than in SR/Jr animals. High salt intake lowered baroreflex sensitivity even in adult SS/Jr rats without affecting it in adult SR/Jr rats. Nevertheless, baroreflex sensitivity was significantly lower in young SS/Jr rats with a severe salt hypertension than in adult ones with a moderate blood pressure elevation. It is concluded that the alterations of baroreflex sensitivity in young inbred SS/Jr rats (including the response to high salt intake) are similar to those described earlier for outbred salt-sensitive Dahl rats. We have, however, disclosed contrasting age-dependent changes of baroreflex sensitivity in both inbred substrains of Dahl rats.
在近亲繁殖的盐敏感（SS/Jr）和盐抵抗（SR/Jr）达尔大鼠中研究了压力反射对心率的控制，这些大鼠在幼年或仅在成年期（即从4周或12周龄开始）接受慢性饮食氯化钠负荷（持续4周）。通过对戊巴比妥麻醉的雄性大鼠给予去氧肾上腺素，我们发现，与年龄匹配的SR/Jr动物相比，喂食低盐饮食的年轻高血压前期SS/Jr大鼠的压力反射敏感性降低（反射性心动过缓的斜率更低）。高盐摄入进一步抑制了年轻SS/Jr大鼠的压力反射敏感性，但对SR/Jr大鼠没有影响。在SR/Jr大鼠中，压力反射敏感性随年龄降低，而在喂食低盐饮食的SS/Jr大鼠中则升高。因此，在16周龄时，SS/Jr大鼠的压力反射敏感性比SR/Jr动物高得多。高盐摄入甚至降低了成年SS/Jr大鼠的压力反射敏感性，而对成年SR/Jr大鼠没有影响。然而，患有严重盐性高血压的年轻SS/Jr大鼠的压力反射敏感性明显低于血压中度升高的成年大鼠。结论是，年轻近亲繁殖的SS/Jr大鼠压力反射敏感性的改变（包括对高盐摄入的反应）与先前描述的远交盐敏感达尔大鼠的改变相似。然而，我们发现达尔大鼠的两个近亲繁殖亚系中压力反射敏感性存在相反的年龄依赖性变化。
