New pathways and data on rapid eye movement sleep behaviour disorder in a rat model.
OBJECTIVE
An abnormality in auditory evoked responses localised to the inferior colliculus (IC) has been reported in rapid eye movement (REM) sleep behaviour disorder (RBD) patients. The external cortex of the inferior colliculus (ICX) has been demonstrated not only to be involved in auditory processing, but also to participate in the modulation of motor activity.


METHODS
Rats were surgically implanted with electrodes for electroencephalography (EEG) and electromyography (EMG) recording and guide cannulae aimed at the ICX for drug infusions. Drug infusions were conducted after the animals recovered from surgery. Polysomnographic recordings with video were analysed to detect normal and abnormal sleep states.


RESULTS
Baclofen, a gamma-aminobutyric acid B (GABAB) receptor agonist, infused into the ICX increased phasic motor activity in slow-wave sleep (SWS) and REM sleep and tonic muscle activity in REM sleep; it also elicited RBD-like activity during the infusion and post-infusion period. In contrast, saclofen, a GABAB receptor antagonist, did not produce significant changes in motor activities in sleep. Baclofen infusions in ICX also significantly increased REM sleep during the post-infusion period, while saclofen infusions did not change the amount of any sleep-waking states.


CONCLUSIONS
This study suggests that GABAB receptor mechanisms in the ICX may be implicated in the pathology of RBD.
Department of Medicine, UCLA, Sepulveda, North Hills, CA 91343, USA.
Kung-Chiao
KC
Hsieh
Darian
D
Nguyen
Jerome M
JM
Siegel
Yuan-Yang
YY
Lai
D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives* / Q000494:pharmacology*; D001933:Brain Stem / Q000502:physiology; D004195:Disease Models, Animal; D004569:Electroencephalography / Q000187:drug effects; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists / Q000494:pharmacology; D007245:Inferior Colliculi / Q000502:physiology; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D017286:Polysomnography / Q000187:drug effects; D020187:REM Sleep Behavior Disorder / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018080:Receptors, GABA-B / Q000502:physiology; D012895:Sleep, REM / Q000187:drug effects* / Q000502:physiology*
D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D018080:Receptors, GABA-B; D001418:Baclofen; C080629:saclofen