Lumbar sympathetic nerve activity and hindquarter blood flow during REM sleep in rats

The present study aimed to investigate the response of lumbar sympathetic nerve activity (LSNA) to the onset of rapid eye movement (REM) sleep and its contribution to the regulation of muscle blood flow during REM sleep in rats. Electrodes for the measurements of LSNA, electroencephalogram, electromyogram and electrocardiogram and a Doppler flow cuff for the measurements of blood flow in the common iliac and mesenteric arteries, also catheters for the measurements of systemic arterial and central venous pressures were implanted chronically. REM sleep resulted in a step increase in LSNA, by 22 +/- 9% (mean +/-S.E.M., P < 0.05), a reduction of iliac vascular conductance, by -16 +/- 3% (P < 0.05) and a gradual increase in systemic arterial pressure, reaching a maximum value of 8.1 +/- 2.0 mmHg (P < 0.05) at 89 s after onset of REM sleep, while mesenteric vascular conductance increased simultaneously by 5 +/- 2% (P < 0.05). There was a significant (Pearson's correlation coefficient = 0.94, P < 0.05) inverse linear relationship between LSNA and the iliac blood flow. Unilateral lumbar sympathectomy blunted the reduction of iliac blood flow induced by the onset of REM sleep. The present observations suggest that the onset of REM sleep appears to be associated with a vasodilation in viscera and a vasoconstriction in skeletal muscle, such that systemic arterial pressure increases during REM sleep in rats.