Sleep spindle dynamics during NREM and REM sleep following distinct general anaesthesia in control rats and in a rat model of Parkinson's disease cholinopathy.

On the basis of our previous studies and the important role of the thalamo-cortical network in states of unconsciousness, such as anaesthesia and sleep, and in sleep spindles generation, we investigated sleep spindles (SS) and high-voltage sleep spindle (HVS) dynamics during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep following different types of general anaesthesia in both physiological controls and in a rat model of Parkinson's disease (PD) cholinopathy, to follow the impact of anaesthesia on post-anaesthesia sleep at the thalamo-cortical level through an altered sleep spindle dynamics. We recorded 6 hr of spontaneous sleep in all rats, both before and 48 hr after ketamine/diazepam or pentobarbital anaesthesia, and we used 1 hr of NREM or REM sleep from each to validate visually the automatically detected SS or HVS for their extraction and analysis. In the controls, SS occurred mainly during NREM, whereas HVS occurred only during REM sleep. Ketamine/diazepam anaesthesia promoted HVS, prolonged SS during NREM, induced HVS of increased frequency during REM, and increased SS/HVS densities during REM versus NREM sleep. Pentobarbital anaesthesia decreased the frequency of SS during NREM and the HVS density during REM sleep. Although the pedunculopontine tegmental nucleus lesion prolonged SS only during NREM sleep, in these rats, ketamine/diazepam anaesthesia suppressed HVS during both sleep states, whereas pentobarbital anaesthesia promoted HVS during REM sleep. The different impacts of two anaesthetic regimens on the thalamo-cortical regulatory network are expressed through their distinct sleep spindle generation and dynamics that are dependent on the NREM and REM state regulatory neuronal substrate.

Sleep disorder and altered locomotor activity as biomarkers of the Parkinson's disease cholinopathy in rat.

In order to find out the possible earliest biomarkers of Parkinson's disease (PD) cholinopathy, we followed the impact of bilateral pedunculopontine tegmental nucleus (PPT) lesion in rat on: the cortical and hippocampal sleep/wake states architectures, all sleep states related EEG microstructures, sleep spindles, the basal and stimulated locomotor activity. Sleep and basal locomotor activity in adult Wistar rats were followed during their inactive circadian phase, and throughout the same aging period. The bilateral PPT lesions were done by 0.1M ibotenic acid (IBO) during the surgical procedure for implantation of the electroencephalographic (EEG) and electromyographic (EMG) electrodes for chronic sleep recording. The cholinergic neuronal loss was identified by NADPH - diaphorase histochemistry. After all sleep and behavioral recording sessions, the locomotor activity was stimulated by d-amphetamine (d-AMPH) and the neuronal activity of striatum was followed by c-Fos immunolabeling. Impaired cholinergic innervation from the PPT was expressed earlier as sleep disorder then as movement disorder, and it was the earliest and long-lasting at hippocampal and thalamo-cortical level, and followed by a delayed "hypokinesia". This severe impact of a tonically impaired PPT cholinergic innervation was evidenced as the cholinergic interneuronal loss of the caudate putamen and as a suppressed c-Fos expression after stimulation by d-AMPH. In order how they occurred, the hippocampal non rapid eye movement (NREM) sleep disorder, altered high voltage sleep spindle (HVS) dynamics during rapid eye movement (REM) sleep in the hippocampus and motor cortex, and "hypokinesia" may serve as the biomarkers of PD cholinopathy onset and progression.

REM sleep disorder following general anesthesia in rats.

Postoperative sleep disorders, particularly the REM sleep disorder, may have a significant deleterious impact on postoperative outcomes and may contribute to the genesis of certain delayed postoperative complications. We have followed the effect of distinct anesthesia regimens (ketamine/diazepam vs. pentobarbital) over 6days following the induction of a stable anesthetized state in adult male Wistar rats, chronically instrumented for sleep recording. In order to compare the effect of both anesthetics in the physiological controls vs. the rats with impaired pedunculopontine tegmental nucleus (PPT) cholinergic innervation, during the operative procedure for the implantation of EEG and EMG electrodes, the bilateral PPT lesion was conducted using ibotenic acid (IBO). We have followed in particular post-anesthesia REM sleep. Our results show the distinct EEG microstructure of the motor cortex during the different stable anesthetized states, and their distinct impact on post-anesthesia REM sleep. In contrast to pentobarbital anesthesia, the ketamine/diazepam anesthesia potentiated the long-lasting post-anesthesia REM statewith higher muscle tone (REM1) vs. REM state with atonia (REM2). Whereas both anesthesias prolonged the post-anesthesia REM sleep duration, the long-term prolongation of the REM1 state was demonstrated only after the ketamine/diazepam anesthesia, first due to the increased number of REM1 episodes, and then due to the prolonged REM1 episodes duration. On the other hand, whereas both anesthetic regimens abolished the prolonged post-anesthesia REM/REM1 sleep and the EEG microstructure disorder during REM sleep, only the pentobarbital abolished the increased NREM/REM/NREM transitions, caused by the PPT lesion. In addition, in the PPT lesioned rats, the ketamine/diazepam anesthesia decreased the Wake/NREM/Wake transitions while the pentobarbital anesthesia decreased the Wake/REM/Wake transitions. Our present study suggests pentobarbital anesthesia as being highly beneficial for post-anesthesia REM sleep in the physiological condition as well as during PPT cholinergic neuropathology.

Age-related disorders of sleep and motor control in the rat models of functionally distinct cholinergic neuropathology.

We studied the impact of aging during sleep in the rat models of Alzheimer's (AD) and Parkinson's (PD) disease cholinergic neuropathology to determine the possible different and earlier onset of age-related sleep disorder during the neurodegenerative diseases vs. healthy aging. We used the bilateral nucleus basalis (NB) and pedunculopontine tegmental nucleus (PPT) lesioned rats as the in vivo models of functionally distinct cholinergic neuropathology, and we followed the impact of aging on sleep architecture, the electroencephalographic (EEG) microstructure and motor control across sleep/wake states. Our results have shown for the first time that the earliest signs of aging during distinct cholinergic neuropathology were expressed through a different and topographically specific EEG microstructure during rapid eye movement sleep (REM). EEG delta amplitude attenuation within the sensorimotor cortex (SMCx) during REM was the earliest sign of aging in the NB lesion. EEG sigma amplitude augmentation within the motor cortex (MCx) during REM was the earliest sign of aging in the PPT lesion. In addition, aging was differently expressed through the SMCx drive alterations, but it was commonly expressed through the MCx drive alterations during all sleep/wake states. Our study provided evidence of distinct REM sleep disorders and sleep state related cortical drives as the signs of aging onset during functionally distinct cholinergic neuropathologies (NB lesion vs. PPT lesion).

Aging induced cortical drive alterations during sleep in rats.

We followed the impact of healthy aging on cortical drive during sleep in rats by using the corticomuscular coherence (CMC). We employed the chronic electrodes implantation for sleep recording in adult, male Wistar rats, and followed the aging impact during sleep from 3 to 5.5 months age. We have analyzed the sleep/wake states architecture, and the sleep/wake state related EEG microstructure and CMCs. We evidenced the topographically distinct impact of aging on sleep/wake states architecture within the sensorimotor (SMCx) vs. motor cortex (MCx) from 4.5 to 5.5 months age. Healthy aging consistently altered only the SMCx sleep/wake states architecture, and increased the delta and beta CMCs through both cortical drives during Wake, but only through the MCx drive during REM. According to the delta and beta CMCs values, aging impact through the SMCx drive was opposite, but it was convergent through the MCx drive during Wake vs. REM, and there was a dual and inverse mode for the motor control during REM.

Glial response in the rat models of functionally distinct cholinergic neuronal denervations.

Alzheimer's disease (AD) involves selective loss of basal forebrain cholinergic neurons, particularly in the nucleus basalis (NB). Similarly, Parkinson's disease (PD) might involve the selective loss of pedunculopontine tegmental nucleus (PPT) cholinergic neurons. Therefore, lesions of these functionally distinct cholinergic centers in rats might serve as models of AD and PD cholinergic neuropathologies. Our previous articles described dissimilar sleep/wake-state disorders in rat models of AD and PD cholinergic neuropathologies. This study further examines astroglial and microglial responses as underlying pathologies in these distinct sleep disorders. Unilateral lesions of the NB or the PPT were induced with rats under ketamine/diazepam anesthesia (50 mg/kg i.p.) by using stereotaxically guided microinfusion of the excitotoxin ibotenic acid (IBO). Twenty-one days after the lesion, loss of cholinergic neurons was quantified by nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry, and the astroglial and microglial responses were quantified by glia fibrillary acidic protein/OX42 immunohistochemistry. This study demonstrates, for the first time, the anatomofunctionally related astroglial response following unilateral excitotoxic PPT cholinergic neuronal lesion. Whereas IBO NB and PPT lesions similarly enhanced local astroglial and microglial responses, astrogliosis in the PPT was followed by a remote astrogliosis within the ipslilateral NB. Conversely, there was no microglial response within the NB after PPT lesions. Our results reveal the rostrorostral PPT-NB astrogliosis after denervation of cholinergic neurons in the PPT. This hierarchically and anatomofunctionally guided PPT-NB astrogliosis emerged following cholinergic neuronal loss greater than 17% throughout the overall rostrocaudal PPT dimension.

REM sleep diversity following the pedunculopontine tegmental nucleus lesion in rat.

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 0.1M ibotenic acid (IBO). Following a recovery period of 2 weeks, we recorded their sleep for 6h. Bilateral PPT lesions were identified by NADPH - diaphorase histochemistry. We applied Fourier analysis to the signals acquired throughout the 6h recordings, and each 10s 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.

Topography of the sleep/wake states related EEG microstructure and transitions structure differentiates the functionally distinct cholinergic innervation disorders in rat.

In order to identify the differences for the onset and progression of functionally distinct cholinergic innervation disorders, we investigated the effect of bilateral nucleus basalis (NB) and pedunculopontine tegmental nucleus (PPT) lesions on sleep/wake states and electroencephalographic (EEG) microstructure in rats, chronically implanted for sleep recording. Bilateral NB lesion transiently altered Wake/NREM duration within the sensorimotor cortex, and Wake/REM duration within the motor cortex, while there was no change in the sleep/wake states distributions following the bilateral PPT lesion. Bilateral PPT lesion sustainably increased the Wake/REM and REM/Wake transitions followed by inconsistent dysregulation of the NREM/REM and REM/NREM transitions in sensorimotor cortex, but oppositely by their increment throughout four weeks in motor cortex. Bilateral NB lesion sustainably decreased the NREM/REM and REM/NREM transitions during four weeks in the sensorimotor cortex, but oppositely increased them in the motor cortex. We have shown that the sustained beta and gamma augmentation within the sensorimotor and motor cortex, and across all sleep/wake states, simultaneously with Wake delta amplitude attenuation only within the sensorimotor cortex, were the underlying EEG microstructure for the sleep/wake states transitions structure disturbance following bilateral PPT lesion. In contrast, the bilateral NB lesion only augmented REM theta in sensorimotor cortex during three weeks. We have shown that the NB and PPT lesions induced differing, structure-related EEG microstructure and transition structure disturbances particularly expressed in motor cortex during NREM and REM sleep. We evidenced for the first time the different topographical expression of the functionally distinct cholinergic neuronal innervation impairment in rat.

Lesion of the pedunculopontine tegmental nucleus in rat augments cortical activation and disturbs sleep/wake state transitions structure.

The pedunculopontine tegmental nucleus (PPT) represents a major aggregation of cholinergic neurons in the mammalian brainstem, which is important in the generation and maintenance of REM sleep. We investigated the effects of unilateral and bilateral PPT lesions on sleep and all the conventional sleep-state related EEG frequency bands amplitudes, in an attempt to find the EEG markers for the onset and progression of PPT cholinergic neuronal degeneration. The experiments were performed on 35 adult male Wistar rats, chronically implanted for sleep recording. During the surgical procedure for EEG and EMG electrodes implantation, the unilateral or bilateral PPT lesion was produced under ketamine/diazepam anesthesia, by the stereotaxically guided microinfusion of 100 nl 0.1M ibotenic acid (IBO) into PPT. We applied Fourier analysis to signals acquired throughout 6h of recordings, and each 10s epoch was differentiated as a Wake, NREM or REM state. We also calculated the group probability density estimates (PDE) of all Wake, NREM and REM conventional EEG frequency amplitudes, and the number of all the transition states using MATLAB 6.5. Our results show that the unilateral or bilateral PPT lesions did not change the sleep/wake architecture, but did change the sleep/wake state transitions structure and the sleep/state related "EEG microstructure". Unilateral or bilateral PPT lesions sustainably increased Wake/REM and REM/Wake transitions from 14 to 35 days after lesions. This was followed by decreased NREM/REM and REM/NREM transitions from 28 days only in the case of the bilateral PPT lesion. The unilateral PPT lesion augmented both Wake theta and REM beta while it also attenuated the relative amplitude of the Wake delta frequency, with a delay of one week. Following a bilateral PPT lesion there was augmentation of the relative amplitude of the Wake, NREM, and REM beta and REM gamma frequency which occurred simultaneously to NREM and Wake delta attenuation. We have shown that the PPT cholinergic neuronal loss sustainably increased the number of the Wake/REM and REM/Wake transitions and augmented sleep-states related cortical activation that was simultaneously expressed by the high frequency amplitude augmentation, as well as Wake and NREM delta frequency attenuation.