Acetylcholine releases of mesopontine PGO-on cells in the lateral geniculate nucleus in sleep-waking cycle and serotonergic regulation.

1. Five adult cats were prepared with standard sleep-recording electrodes, microinjection cannulae in the bilateral mesopontine tegmentum X area and cannulae for microdialysis probes in the LGN. 2. Dialysates were collected at 5 min intervals during SWS, REM sleep and wakefulness, and during pre- and post-stimulation periods of 5MeODMT microinjection in the bilateral mesopontine tegmentum of freely moving cats. 3. A REM sleep-specific increase of ACh release was observed in the LGN, but not out of the LGN. 4. ACh release was depressed up to 33% by bilateral 5MeODMT microinjection in the mesopontine tegmentum where the microinjection of carbachol also depressed ACh in the LGN probably by stimulating the auto receptor. 5. Our observations indicate that PGO-on neurons of mesopontine tegmentum release more ACh in the LGN during REM sleep by burst discharge than during wakefulness and SWS, and that presumptive cholinergic PGO-on cells are regulated by serotonergic inputs.