HYDRALAZINE REDUCES ELEVATED SLEEP-APNEA INDEX IN SPONTANEOUSLY HYPERTENSIVE (SHR) RATS TO EQUIVALENCE WITH NORMOTENSIVE WISTAR-KYOTO RATS

The effects of lowering blood pressure (BP) by hydralazine (HY) (2 mg/ kg) on spontaneous (SA) and post-sigh (PSA) sleep apneas have been stu died in spontaneously hypertensive (SHR) rats by monitoring their resp iration and sleep by the EEG for 6 hours. Normotensive Wistar-Kyoto (W KY) rats, from which the SHR rat strain was derived, were used as an a ppropriate control. The SHR rats had more SA (p < 0.02) and PSA (p < 0 .0001) apneas/hour than WKY rats during nonrapid eye movement sleep an d their mean BP was higher by 40 mm Hg (p < 0.0001) than WKY rats. Adm inistration of HY to SHR rats equalized their BP with the arterial pre ssure of WKY rats and reduced the SA and the PSA apneas/hour to equiva lence with WKY normotensive rats. These results demonstrate that even in the context of lifelong hypertension, acute normalization of BP sig nificantly reduces sleep apneas in rats. They further suggest that imp roved management of BP may be of clinical benefit to patients with apn ea who have long-standing hypertension.