Abated cardiovascular responses to chronic oral lisinopril treatment in conscious elderly rats

To determine whether the cardiovascular effects of chronic treatment with lisinopril are age related, we compared baroreflex sensitivity and presser responsiveness in 4-mo- and 21-mo-old male rats that had been given oral lisinopril daily for 4 wk. Reflex bradycardia elicited by elevating blood pressure with phenylephrine was stronger in 4-mo-old rats than it was in al-mo-old rats and also stronger in lisinopril-treated rats than it was in untreated rats of the same age. Presser responses to angiotensin or narepinephrine were recorded after combined cholinergic and beta-adrenergic blockade and then analyzed not only as absolute but also as percent increases in mean pressure. Although presser responses seemed to be slightly reduced by lisinopril when expressed as absolute increases in mean pressure, corresponding percent increases were always larger in 4-mo-old rats than they were in 21-mo-old rats and were clearly enhanced by lisinopril more in younger rats. The stronger overall enhancement of presser responsiveness- and reflex bradycardia in younger rats suggests that the cardiovascular effects of lisinopril diminish with advancing age.