Abnormal blood pressure behaviour produced by intracerebral angiotensin during natural sleep

The influence of the intracerebroventricular infusion of angiotensin II (Ang II) on the pattern of arterial pressure changes during natural sleep was studied in rats. The wakefulness-sleep cycle was observed during a sleep session of approximately 8 h in a group of rats (n = 7) receiving Ang II infusion, whereas the control group (n = 7) received a saline infusion. Angiotensin II infusion increased the time spent by the rats in sleep (75 versus 45% for saline infusion): both synchronized sleep and desynchronized sleep increased (50 versus 35% and 25 versus 10% in rats receiving Ang II and saline, respectively). Therefore, the increase produced by infusion of Ang II in desynchronized sleep was proportionally larger than the increase in synchronized sleep (150 versus 42%). Intracerebroventricular infusion of Ang II increased the arterial pressure during quiet wakefulness [124 +/- 3.0 (s.e.m.) versus 115 +/- 3.0 mmHg]. In 85 episodes of synchronized sleep the mean arterial pressure increased (6.0 +/- 2.0 mmHg), and it decreased in 50 episodes of desynchronized sleep (-12 +/- 2.0 mmHg) in rats treated with Ang II. In control rats the saline infusion produced no change in mean arterial pressure measured in quiet wakefulness (118 +/- 3.0 versus 116 +/- 3.0 mmHg). During 44 episodes of synchronized sleep the arterial pressure remained unaltered (2.0 +/- 1.0 mmHg), and it increased as in normal rats in 30 episodes of desynchronized sleep (5.0 +/- 1.0 mmHg). The data indicate that Ang II alters blood pressure regulation during sleep, a natural behaviour, probably by interfering with the central modulation of the baroreceptor reflexes.