Study objectives: Although blood pressure during sleep and the difference in blood pressure between sleep and wakefulness carry prognostic information, little is known on their central neural mechanisms. Hypothalamic neurons releasing hypocretin (orexin) peptides control wake-sleep behavior and autonomic functions and are lost in narcolepsy-cataplexy. We investigated whether chronic lack of hypocretin signaling alters blood pressure during sleep.
Design: Comparison of blood pressure as a function of the wake-sleep behavior between 2 different hypocretin-deficient mouse models and control mice with the same genetic background.
Setting: N/A.
Subjects: Hypocretin-ataxin3 transgenic mice with genetic ablation of hypocretin neurons (TG, n = 12); hypocretin gene knock-out mice (KO, n = 8); congenic wild-type controls (WT, n = 10).
Interventions: Instrumentation with electrodes for sleep recordings and a telemetric blood pressure transducer.
Measurements and results: Blood pressure was significantly higher in either TG or KO than in WT during non-rapid eye movement sleep (NREMS; 4 ± 2 and 7 ± 2 mm Hg, respectively) and rapid eye movement sleep (REMS; 11 ± 2 and 12 ± 3 mm Hg, respectively), whereas it did not differ significantly between groups during wakefulness. Accordingly, the decrease in blood pressure between either NREMS or REMS and wakefulness was significantly blunted in TG and KO with respect to WT.
Conclusions: Chronic lack of hypocretin signaling may entail consequences on blood pressure that are potentially adverse and that vary widely among wake-sleep states.
Keywords: Hypertension; nervous system; peptides; physiology; sleep.