Two types of neurons are involved in the regulation of rapid eye movement (REM) sleep, the REM-ON and the REM-OFF neurons. As the name suggests, the REM-OFF neurons cease firing during REM sleep and they are norepinephrinergic. It has been shown that cessation of these neurons is a pre-requisite for the generation of REM sleep and GABA shuts them off. Further, if these neurons do not shut off, there is increased levels of norepinephrine in the brain and loss of REM sleep. The REM sleep deprivation induced increase in norepinephrine is responsible for mediating at least REM sleep loss induced increase in Na(+)-K(+) ATPase activity, which is likely to be the primary factor for causing REM sleep deprivation induced effects.