Brainstem Acetylcholine Release and REM Sleep

Many recent studies indicate that acetylcholine (ACh) in the brainstem is involved in REM sleep generation. Local ACh release in the brainstem regions, responsible for REM sleep during sleep and wakefulness, has not so far been reported because of technical difficulties. With in vivo microdialysis and electrochemical detection, we investigated the relationship between ACh release and sleep-wake stages in the dorsolateral pohs, the nucleus magnocellularis(NMC) and the nucleus paramedianus of the medulla of cats, which are indispensable for REM sleep generation, and the nucleus caudatus, as a control region. There were two patterns of ACh release in relation to sleep-wake stages; ACh release was significantly highest during REM sleep, or else it was not significantly different among sleep-wake stages'(wakefulness, slow-wave sleep and REM sleep). The REM sleep-specific enhancement of ACh release was observed in the dorsolateral pons and NMC, thus indicating the involvement of REM sleep-related cholinergic mechanisms in these regions. In the current paper, we report further studies of the pontine and medullary regions implicated in REM control with the microdialysis technique. We found that the medullary glutamate receptive neurons modulate both ACh release in the pons and REM sleep duration. Glutamate application within the pons produced an increase followed by a decrease in ACh release. These results indicate that interactions between glutamatergic and cholinergic cells in NMC and dorsolateral pons are important in REM sleep control.