Changes in 24-hour urinary excretion of MHPG after four continuous nights of REM sleep deprivation in human volunteers

Eight healthy volunteers were deprived of rapid eye movement (REM) sleep for 4 consecutive nights. Twenty-four-hour urine samples were collected to determine levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) during basal, REM sleep deprivation, and REM recovery conditions. A control experiment was carried out in four subjects who were awakened in non-REM sleep for 4 consecutive nights. Subjects deprived of REM sleep showed significant MHPG increases on night 4 of sleep deprivation. MHPG levels in the control condition decreased, but not significantly. When MHPG levels in both experimental and control conditions were compared in the same four subjects, a significant difference was observed, indicating an effect of the control condition. Increased MHPG levels were related to REM sleep reduction and to the time and number of awakenings. Our findings seem to support an inverse homeostatic relationship between norepinephrine metabolism and REM sleep.