title: A Temporally Controlled Inhibitory Drive Coordinates Twitch Movements during REM Sleep.
abstract: During REM sleep, skeletal muscles are paralyzed in one moment but twitch and jerk in the next. REM sleep twitches are traditionally considered random motor events that result from momentary lapses in REM sleep paralysis [1-3]. However, recent evidence indicates that twitches are not byproducts of REM sleep, but are in fact self-generated events that could function to promote motor learning and development [4-6]. If REM twitches are indeed purposefully generated, then they should be controlled by a coordinated and definable mechanism. Here, we used behavioral, electrophysiological, pharmacological, and neuroanatomical methods to demonstrate that an inhibitory drive onto skeletal motoneurons produces a temporally coordinated pattern of muscle twitches during REM sleep. First, we show that muscle twitches in adult rats are not uniformly distributed during REM sleep, but instead follow a well-defined temporal trajectory. They are largely absent during REM initiation but increase steadily thereafter, peaking toward REM termination. Next, we identify the transmitter mechanism that controls the temporal nature of twitch activity. Specifically, we show that a GABA and glycine drive onto motoneurons prevents twitch activity during REM initiation, but progressive weakening of this drive functions to promote twitch activity during REM termination. These results demonstrate that REM twitches are not random byproducts of REM sleep, but are instead rather coherently generated events controlled by a temporally variable inhibitory drive.
authors.affiliation: Department of Cell and Systems Biology, Centre for Biological Timing and Cognition, University of Toronto, Toronto, ON M5S 3G5, Canada.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Brooks
authors.affiliation: Department of Cell and Systems Biology, Centre for Biological Timing and Cognition, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 3G5, Canada. Electronic address: john.peever@utoronto.ca.
authors.forename: John
authors.initials: J
authors.lastname: Peever
mesh_terms: D000818:Animals; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D018377:Neurotransmitter Agents; D051381:Rats; D011963:Receptors, GABA-A / Q000502:physiology; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors / Q000378:metabolism; D012895:Sleep, REM / Q000502:physiology*; D013997:Time Factors
chemical_list: D058787:GABA-A Receptor Antagonists; D018377:Neurotransmitter Agents; D011963:Receptors, GABA-A; D018009:Receptors, Glycine
keywords: GABA; REM sleep; REM sleep behavior disorder; glycine; motoneuron; motor control; motor plasticity; muscle twitches