Membrane potential of spinal motoneurons during natural sleep in cats.

The membrane potential of spinal motoneurons was recorded during wakefulness, NREM sleep, and REM sleep in minimally restrained, behaving cats. At the onset of sleep, the membrane potential generally increased in polarization in rough proportion to time spent asleep. During the postural atonia of REM sleep, the membrane potential of all motoneurons was tonically hyperpolarized. Antecedents of NREM sleep electromyographic suppressions, and REM sleep myoclonic twitches were seen as transient hyperpolarizations and depolarizations, respectively.