Central Attenuation of Baroreflex Precedes the Development of Hypertension in DOCA- SALT-Treated Rats

To determine whether baroreflex is changed centrally before the development of hypertension in DOCA-salt treated rats, aortic depressor nerve was stimulated electrically 5 days after DOCA-salt treatment in ure-thane-anesthetized rats: compared with those of sham-operated control rats, blood pressure was not elevated in either awake or anesthetized rats. Aortic depressor nerve (ADN) stimulation elicited frequency-dependent vasode pressor, bradycardiac, and sympatho-inhibitory responses in both DOCA-salt-treated and control rats. However, the responses to ADN stimulation were significantly smaller in DOCA-salt-treated rats. These findings suggest that baroreflex is attenuated centrally before the development of hypertension and this attenuation may contribute to the pathogenesis of DOCA-salt hyperten sion. Am J Hypertens 1988;1:23S-25S KEY WORDS: Baroreflex; aortic depressor nerve, blood pressure, sympathetic nerve activity, DOCA-salt hypertension. Baroreflex dysfunction has been reported in several studies of experimental hypertension.1 Recently, it has been discovered that baroreflex changes occur before the development of hy pertension. In Dahl rats, heart rate control mediated by baroreflex is impaired before the development of hy pertension. 2, 3 However, the mechanism of sympathetic nerve regulation by baroreflex is not yet clear. It is likely that baroreflex abnormality can contribute to the devel opment of hypertension because the elimination of bar oreflex can produce hypertension by DOCA-sal t treat ment in Sabra rats. 4 Recently, it was found that baroreflex is impaired centrally in experimental hypertension. 5 " 7 The impair ment is found in hypertensive stage. Whether or not th