Differential effects of behaviour on sympathetic outflow during sleep and exercise

The responses of renal and lumbar sympathetic outflow to changes in behavioural states were reviewed in this paper. During rapid eye movement (REM) sleep, renal sympathetic nerve activity was decreased while lumbar sympathetic nerve activity increased. These diverse changes in sympathetic nerve activity observed during REM sleep help explain the responses in regional blood flow to REM sleep; that is renal blood flow increased while muscle blood flow decreased. By contrast, exercise increased both renal and muscle sympathetic nerve activity. The degree of physical activity was correlated with the magnitude of the increases in renal and muscle sympathetic nerve activity. There was a significant (P<0.05) linear relationship between renal sympathetic nerve activity and systemic arterial pressure over the transition between non-rapid eye movement (NREM) sleep, quiet awake, moving and grooming states in the rats. This suggests that sympathetic outflows seem to be modulated quantitatively to meet cardiovascular demand caused by changes in the level of physical activity. It is therefore concluded that sympathetic outflow seems to be regulated in a state-specific manner during sleep and exercise.