Short term rapid eye movement (REM) sleep deprivation produced a decrease in walking discharge rates of presumably noradrenergic pontine 'REM sleep-off' cells and an increase in waking discharge rates of pontine 'REM sleep-on' cells. These changes can be viewed as a correlate of increased REM sleep pressure. Slowing of REM sleep-off cells in waking is hypothesized to counteract the functional effects of REM sleep loss on noradrenergic receptor sensitivity. This slowing and the resulting reduction in norepinephrine release may contribute to the loss of vigilance seen with sleep deprivation.