Which neurotransmitter system is primarily responsible for the muscle atonia (REM atonia) seen during REM sleep, and what is the clinical consequence of its failure?

• A Serotonin from raphe nuclei; failure causes narcolepsy with cataplexy
• B Dopamine from ventral tegmentum; failure causes restless legs syndrome
• C GABA and glycine actively hyperpolarising spinal motor neurons; failure causes REM sleep behaviour disorder ✓
• D Acetylcholine from pedunculopontine nucleus; failure causes sleep apnoea

Explanation

During REM sleep, descending pathways originating in the sublateral dorsal nucleus and ventral medial medulla release GABA and glycine onto spinal alpha-motor neurons, producing the post-synaptic inhibition (active hyperpolarization) responsible for REM atonia. When this system fails — as in REM sleep behaviour disorder (RBD), associated with alpha-synucleinopathies — patients physically act out their dreams. RBD is often a prodrome of Parkinson's disease or Lewy body dementia by years to decades.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.