Pedersen NP, Anaclet C, Vetrivelan R, Saper CB, Lu J (2008) The retroabducens region is necessary for rapid eye movement (REM) during REM sleep in the rat. Neuroscience 2008 Abstracts 784.15/RR66. Society for Neuroscience, Washington, DC.
Summary: REM sleep is characterized by REMs, atonia of the non-respiratory musculature, and active dreaming during which the electroencephalogram (EEG) is desynchronized in humans and shows increased theta activity in rodents. Surprisingly, the source of the actual REMs during REM sleep is not known, although Pompeiano and Morrison (1965) described the reduction or absence of phasic REM phenomena after electrolytic lesion of the medial and spinal vestibular nuclei in the cat. Using the neurotoxins ibotenic acid and saporin-conjugated anti-orexin B IgG, we systematically placed cell-specific lesions in brainstem candidate structures for the generation of REMs in rats equipped for chronic recording of EEG, electrooculogram, and electromyogram. Lesion of a ‘retroabducens’ area, located immediately caudal and extending ventrally from the abducens nucleus, although leaving the abducens nucleus intact, abolished REMs (as well as waking saccades), without affecting other aspects of REM sleep. Animals with retroabducens lesions showed maintenance of slow oscillations in eye position, characteristic of non-REM or slow wave sleep, throughout REM sleep. Lesions of the medial vestibular nucleus, nucleus prepositus hypoglossi and immediately rostral to abducens did not affect REMs. We hypothesize that the retroabducens area may be required for the generation of saccadic eye movements, similar to the paramedian pontine reticular formation as described in cats and monkeys. The retroabducens region appears to be critical for generating the REMs that characterize REM sleep, but most likely downstream from the REM sleep generator.
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