Vagal afferent activation induces a dissociated NREM sleep-like state with wake-related locus coeruleus activity

Parasympathetic nervous system activity, vital for restorative sleep, is influenced by vagal sensory afferents, but how these shape brain-body correlates of sleep remains open. Here we combined vagal sensory neuron (VSN) stimulation in the mouse with EEG/EMG, heart rate, brain-body temperature, noradrenergic locus coeruleus (LC) neuron population activity measures and in vitro synaptic physiology to investigate the effects of VSN activation on sleep-wake states. We show that chemogenetic VSN stimulation during the resting phase induced a non-rapid-eye-movement sleep (NREMS)-like state with enriched, but homeostatically regulated, low-frequency (0.75–4 Hz) EEG activity, yet suppressed REMS. Simultaneously, brain-body temperatures dropped while LC activity increased. The gradual recovery towards normal NREMS-REMS-cycles was accelerated by external warming, identifying cooling as key contributing factor. We conclude that VSN activation can promote brain-body correlates as a continuum of normal NREMS while engaging wake-promoting forebrain neuromodulation, revealing a coexistence of classically incompatible sleep- and wake-associated signatures.