Surges of arterial pressure during rapid-eye-movement sleep in spontaneously hypertensive rats

Study Objectives: rapid-eye-movement sleep (REMS) physiologically entails arterial pressure surges. Pressure surges may lead to acute cardiovascular events in risk conditions such as arterial hypertension. We investigated whether arterial hypertension alters the rate of occurrence and the characteristics of the pressure surges during REMS. Design: Spontaneously Hypertensive Rats (SHR) were compared with Wistar-Kyoto normotensive controls (WKY) and a group of SHR, in which hypertension was prevented by long-term enalapril treatment (ena-SHR). Patients or Participants: seven male rats per group. Interventions: instrumentation with electrodes for polygraphic recordings, a nasal thermistor for measuring ventilatory period, and an arterial catheter for measuring arterial pressure and heart period. Measurements and Results: SHR showed a significant increase in the rate of occurrence but a similar magnitude of the pressure surges during REMS with respect to WKY and ena-SHR. The pressure surges were associated with a decrease of heart period and an increase of electroencephalographic theta frequency, which were significantly less pronounced in SHR than either in WKY or ena-SHR. The ventilatory period showed only a modest increase before the surges without significant differences among the groups. Conclusions: Pressure surges independent of sleep apnea occur during REMS at a rate increased in SHR with respect to their controls, supporting a potential role of REMS in triggering acute cardiovascular events in arterial hypertension. The characteristics of the pressure surges suggest that in SHR, the underlying central autonomic commands are increased in frequency, but not in magnitude, by arterial hypertension.