Alteration in baroreceptor function in rats produces typical pressure changes during sleep.

We have shown previously that both sinoaortic denervation (SAD) and high renin hypertension in the rat produce a pronounced alteration in the pattern of pressure change during sleep, namely from unchanged to a rise in pressure during synchronized sleep (SS) and from a slight rise to a marked fall during desynchronized sleep (DS). Since acute SAD also produces overactivity of the renin-angiotensin system (RAS), we investigated if this overactivity is essential for the development of the alterations. In rats studied 1 day after SAD (138 +/- 1.0 mm Hg) the MAP rose during SS (+14 +/- 0.7 vs. +1.0 +/- 0.16 mm Hg in the controls) and fell during DS (-27.2 +/- 1.5 vs. 4.9 +/- 0.6 mm Hg in the controls). Captopril-treated rats, studied 1 day after SAD (89 +/- 1.2 mm Hg), also exhibited rise in pressure during SS (+12.3 +/- 0.6 mm Hg) and fall during DS (-12.8 +/- 1.7 mm Hg). Similar alterations were observed in rats studied 10 days after SAD (116 +/- 0.7 mm Hg) when RAS activity was normal (PRA: 1.3 +/- 0.2 vs. 10.4 +/- 2.7 ng AI/ml/h for SAD-1 day); the MAP rose during SS (+6.5 +/- 0.3 mm Hg) and fell during DS (-5.0 +/- 0.9 mm Hg). These data indicate that impairment of the baroreceptor function per se determines the typical alteration in the pattern of pressure change during sleep in the rat.