Effects of chemogenetic inhibition of mesopontine cholinergic neurons on REM sleep and PGO waves in mice

Sleep is present throughout the animal kingdom, but its function remains to be fully determined. Rapid eye movement sleep (REM) is characterised by muscle atonia, heightened theta oscillations, and the occurrence of ponto-geniculo-occipital (PGO) waves or P-waves. The pedunculopontine and laterodorsal tegmental nuclei (PPT/LDT) have been implicated in REM sleep generation, and their cholinergic neuronal activity was specifically associated with P-waves. However, the precise role of pontine cholinergic neurons in REM sleep remains elusive, particularly their impact on sleep architecture and P-wave dynamics.In this study, we used a chemogenetic approach to inhibit cholinergic neurons in the PPT/LDT and assessed the effects on sleep architecture and P-waves in mice. We expressed hM4Di receptors in a Cre-dependent manner in the PPT/LDT of ChAT-Cre mice and recorded P-waves using a bipolar electrode. Electrophysiological recordings of electroencephalography (EEG) and electromyography (EMG) signals in freely behaving conditions enabled the characterisation of sleep states. Various doses of clozapine-N-oxide (CNO) or vehicle control were administered over different 10-hour recording sessions to selectively inhibit PPT/LDT cholinergic neurons.In this presentation, we will discuss how PPT/LDT cholinergic neurons affect REM sleep induction and maintenance as well as if PPT/LDT cholinergic neurons are necessary to induce P-waves.