Two novel mouse models of slow-wave-sleep enhancement in aging and Alzheimer's disease

Disruption of sleep macro- and microstructure in Alzheimer's disease: overlaps between neuropsychology, neurophysiology, and neuroimaging

Alzheimer's disease (AD) is the leading cause of dementia, often associated with impaired sleep quality and disorganized sleep structure. This study aimed to characterize changes in sleep macrostructure and K-complex density in AD, in relation to neuropsychological performance and brain structural changes. We enrolled 30 AD and 30 healthy control participants, conducting neuropsychological exams, brain MRI, and one-night polysomnography. AD patients had significantly reduced total sleep time (TST), sleep efficiency, and relative durations of non-rapid eye movement (NREM) stages 2 (S2), 3 (S3), and rapid eye movement (REM) sleep (p < 0.01). K-complex (KC) density during the entire sleep period and S2 (p < 0.001) was significantly decreased in AD. We found strong correlations between global cognitive performance and relative S3 (p < 0.001; r = 0.86) and REM durations (p < 0.001; r = 0.87). TST and NREM stage 1 (S1) durations showed a moderate negative correlation with amygdaloid and hippocampal volumes (p < 0.02; r = 0.51-0.55), while S3 and REM sleep had a moderate positive correlation with cingulate cortex volume (p < 0.02; r = 0.45-0.61). KC density strongly correlated with global cognitive function (p < 0.001; r = 0.66) and the thickness of the anterior cingulate cortex (p < 0.05; r = 0.45-0.47). Our results indicate significant sleep organization changes in AD, paralleling cognitive decline. Decreased slow wave sleep and KCs are strongly associated with cingulate cortex atrophy. Since sleep changes are prominent in early AD, they may serve as prognostic markers or therapeutic targets.

To sleep or not to sleep - Effects on memory in normal aging and disease

Sleep behavior undergoes significant changes across the lifespan, and aging is associated with marked alterations in sleep amounts and quality. The primary sleep changes in healthy older adults include a shift in sleep timing, reduced slow-wave sleep, and impaired sleep maintenance. However, neurodegenerative and psychiatric disorders are more common among the elderly, which further worsen their sleep health. Irrespective of the cause, insufficient sleep adversely affects various bodily functions including energy metabolism, mood, and cognition. In this review, we will focus on the cognitive changes associated with inadequate sleep during normal aging and the underlying neural mechanisms.

Validation of DREADD agonists and administration route in a murine model of sleep enhancement

BACKGROUND

Chemogenetics is a powerful tool to study the role of specific neuronal populations in physiology and diseases. Of particular interest, in mice, acute and specific activation of parafacial zone (PZ) GABAergic neurons expressing the Designer Receptors Activated by Designer Drugs (DREADD) hM3Dq (PZ^GABA-hM3Dq) enhances slow-wave-sleep (SWS), and this effect lasts for up to 6 h, allowing prolonged and detailed study of SWS. However, the most widely used DREADDs ligand, clozapine N-oxide (CNO), is metabolized into clozapine which has the potential of inducing non-specific effects. In addition, CNO is usually injected intraperitoneally (IP) in mice, limiting the number and frequency of repeated administration.

NEW METHODS

The present study is designed to validate the use of alternative DREADDs ligands-deschloroclozapine (DCZ) and compound 21 (C21)-and a new administration route, the voluntary oral administration.

RESULTS

We show that IP injections of DCZ and C21 dose-dependently enhance SWS in PZ^GABA-hM3Dq mice, similar to CNO. We also show that oral administration of CNO, DCZ and C21 induces the same sleep phenotype as compared with IP injection.

COMPARISON WITH EXISTING METHODS AND CONCLUSION

Therefore, DCZ and C21 are powerful alternatives to the use of CNO. Moreover, the voluntary oral administration is suitable for repeated dosing of DREADDs ligands.