Baroreceptor function during natural sleep in rats with mild and severe renal hypertension.

1. Mean arterial pressure (MAP) changes during natural sleep of rats with mild renal hypertension (MAP less than 160 mmHg) were similar to those of normotensive rats. No significant change in MAP was observed in 35 episodes of synchronized sleep (SS) but a significant increase (6.2 +/- 1.4 mmHg) was detected in 23 episodes of desynchronized sleep (DS). 2. Rats with severe renal hypertension (MAP greater than 160 mmHg) behaved more like rats with sinoaortic denervation. MAP increased significantly (6.1 +/- 1.4 mmHg) in 40 episodes of SS studied in 8 rats. In 6 of these rats MAP decreased during DS, while in the other 2 it increased. When all 39 episodes of DS were considered, the decrease in MAP (2.2 +/- 1.5 mmHg) was not statistically significant. 3. Sinoaortic denervation increased the MAP of 3 rats with mild renal hypertension from 154 +/- 4 to 181 +/- 21 mmHg. In 30 episodes of SS MAP increased (19.0 +/- 3.0 mmHg) and in 16 episodes of DS, MAP decreased markedly (27.0 +/- 5.0 mmHg). 4. These data suggest that rats with severe renal hypertension have altered baroreceptor function during natural sleep that is probably due to modification of the central integration of the baroreceptor reflex.