Eriksson L, Kerecsen L, Buñag R D
Department of Pharmacology, University of Kansas Medical Center.
J Gerontol. 1991 Mar;46(2):B65-71. doi: 10.1093/geronj/46.2.b65.
To determine whether inhibition of the brain renin-angiotensin system would affect baroreflexes similarly in old rats of different strains, we compared 24-month-old male Fischer 344 and Sprague-Dawley rats. Baroreflex sensitivity was tested while the rats were awake by recording reflex heart rate responses elicited as blood pressure was elevated with phenylephrine or lowered with sodium nitroprusside. Sprague-Dawley rats had higher blood pressures and lower heart rates initially. Chronic infusion of enalapril, a converting enzyme inhibitor, into a lateral cerebral ventricle (ICV) for two weeks lowered blood pressure in Sprague-Dawley but not in Fischer 344 rats. Furthermore, reflex bradycardia was unaffected in either rat strain, but reflex tachycardia was selectively suppressed in Fischer 344 rats. Thus, although time controls were not done to rule out spontaneous changes during the 14-day infusion period, these results suggest that central cardiovascular regulation does not change similarly with age in these two rat strains. As removal of the brain renin-angiotensin system lowered blood pressure in one strain and inhibited reflex tachycardia in the other, the divergence could mean that the brain renin-angiotensin system acts differently to keep blood pressure elevated in Sprague-Dawley rats and modulate reflex tachycardia in Fischer 344 rats.
为了确定抑制大脑肾素-血管紧张素系统是否会对不同品系的老年大鼠的压力反射产生类似影响，我们比较了24月龄的雄性Fischer 344大鼠和Sprague-Dawley大鼠。在大鼠清醒时，通过记录用去氧肾上腺素升高血压或用硝普钠降低血压时引发的反射性心率反应来测试压力反射敏感性。Sprague-Dawley大鼠最初的血压较高，心率较低。向侧脑室（ICV）慢性输注血管紧张素转换酶抑制剂依那普利两周可降低Sprague-Dawley大鼠的血压，但对Fischer 344大鼠无效。此外，两种品系大鼠的反射性心动过缓均未受影响，但Fischer 344大鼠的反射性心动过速被选择性抑制。因此，尽管未进行时间对照以排除14天输注期内的自发变化，但这些结果表明，这两种品系大鼠的中枢心血管调节随年龄的变化并不相似。由于去除大脑肾素-血管紧张素系统在一个品系中降低了血压，而在另一个品系中抑制了反射性心动过速，这种差异可能意味着大脑肾素-血管紧张素系统在Sprague-Dawley大鼠中升高血压的作用不同，而在Fischer 344大鼠中调节反射性心动过速。
