Research reportREM sleep diversity following the pedunculopontine tegmental nucleus lesion in rat

- Pedunculopontine tegmental nucleus (PPT) is a source of thalamo-cortical innervation.
- PPT cholinergic neuronal loss potentiated the emergence of two REM sleep states.
- Pathological REM1 and REM2 have differential total EMG power.
- REM1 and REM2 have topographically distinct EEG microstructures.
- REM1 and REM2 have distinct cortical drive to dorsal nuchal musculature.

The aim of this study was to demonstrate that two REM clusters, which emerge following bilateral pedunculopontine tegmental nucleus (PPT) lesions in rats, are two functionally distinct REM states.We performed the experiments in Wistar rats, chronically instrumented for sleep recording. Bilateral PPT lesions were produced by the microinfusion of 100 nl of 0.1 M ibotenic acid (IBO). Following a recovery period of 2 weeks, we recorded their sleep for 6 h. Bilateral PPT lesions were identified by NADPH - diaphorase histochemistry.We applied Fourier analysis to the signals acquired throughout the 6 h recordings, and each 10 s epoch was differentiated as a Wake, NREM or REM state. We analyzed the topography of the sleep/wake states architecture and their transition structure, their all state-related EEG microstructures, and the sensorimotor (SMCx) and motor (MCx) cortex REM related cortico-muscular coherences (CMCs).Bilateral PPT lesion in rats increased the likelihood of the emergence of two distinct REM sleep states, specifically expressed within the MCx: REM1 and REM2. Bilateral PPT lesion did not change the sleep/wake states architecture of the SMCx, but pathologically increased the duration of REM1 within the MCx, alongside increasing Wake/REM1/Wake and NREM/REM2/NREM transitions within both cortices. In addition, the augmented total REM SMCx EEG beta amplitude and REM1 MCx EEG theta amplitude was the underlying EEG microstructure pathology.PPT lesion induced REM1 and REM2 are differential states with regard to total EMG power, topographically distinct EEG microstructures, and locomotor drives to nuchal musculature.