Functional Role of Diverse Changes in Sympathetic Nerve Activity in Regulating Arterial Pressure during REM Sleep

Study Objectives: This study aimed to investigate whether REM sleep evoked diverse changes in sympathetic outflows and, if so, to elucidate why REM sleep evokes diverse changes in sympathetic outflows. Measurements: Male Wistar rats were chronically implanted with electrodes to measure renal (RSNA) and lumbar sympathetic nerve activity (LSNA), electroencephalogram, electromyogram, and electrocardiogram, and catheters to measure systemic arterial and central venous pressure; these parameters were measured simultaneously and continuously during the sleep-awake cycle in the same rat. Results: REM sleep resulted in a step reduction in RNSA by 36.1% +/- 2.7% (p < 0.05), while LSNA increased in a step manner by 15.3% +/- 2% (P < 0.05) relative to the NREM level. Systemic arterial pressure increased gradually (P < 0.05), while heart rate decreased in a step manner (P < 0.05) during REM sleep. In contrast to REM sleep, RNSA, LSNA, systemic arterial pressure, and heart rate increased in a unidirectional manner associated with increased in physical activity levels in the order from NREM sleep, quiet awake, moving, and grooming state. Thus, the relationship between RSNA vs. LSNA and systemic arterial pressure vs. heart rate observed during REM sleep was dissociated compared with that obtained during the other behavioral states. Conclusions: It is suggested that the diverse changes in sympathetic outflows during REM sleep may be needed to increase systemic arterial pressure by balancing vascular resistance between muscles and vegetative organs without depending on the heart.