Abstract: PURPOSE: The oculomotor nucleus (OMN) in midbrain is a well-known center for eye movements (EMs). As a paradigmatic behavior, EMs showed distinct activation patterns in rapid eye movement (REM) and non-REM (NREM) sleep stages. Previous studies indicates that OMN may be involved in the regulation of EMs during REM sleep. However, it is still unclear whether the neurons in OMN participated in regulating sleep states and how they modulate different sleep states and EMs separately.
METHODS: To explain the structurally and functionally basis of OMN cholinergic (OMNChAT) neurons in regulating EM in REM sleep, viral tracing, immunohistochemical techniques, in vivo or vitro electrophysiology, deep-brain calcium imaging and optogenetic stimulation during polygraphic recordings were conducted.
RESULTS: In this study, we found that a subset of cholinergic neurons within the OMN were active during sleep and exhibited increased activity before REM sleep ends, especially during transitions from REM sleep to wakefulness. Through the application of optogenetic manipulation and calcium imaging, we revealed the existence of functional heterogeneity among OMN neurons and identify a subset of cholinergic neurons which did not control EMs could terminate REM sleep. We identified the nucleus papilio (NP) as a potential effector pathway in lighting the OMN for initiation of REM-off.
CONCLUSIONS: Our results suggested that OMN is a key node that possesses functionally segregated subpopulations capable of parallel, independent control of EMs and sleep.

Key words: Rapid eye movement sleep, Oculomotor nucleus, Cholinergic neurons