Sleep-state related EEG amplitude distribution in the rat model of cortical cholinergic innervation disorder

Abstract

We examined the effects of unilateral and bilateral nucleus basalis (NB) lesion in rat on sleep/wake states, and sleep/wake state-related electroencephalographic (EEG) frequency relative amplitude distributions. We aimed this study to identify the possible EEG markers for the onset and progression of cortical cholinergic neurodegeneration in rats. NB lesion was performed by ibotenic acid (IBO) microinfusion, and identified by NADPH-diaphorase histochemistry. Sleep/wake states related EEG relative amplitude analysis was done using the Probability Density Estimate (PDE) routine supplied with MATLAB 6.5. Bilateral NB lesion transiently altered gross sleep/wake states topography 14 days following lesion. While control rats exhibited equivalent durations of Wake, NREM and REM, as determined by sensorimotor versus motor cortex EEG, bilateral NB lesion decreased Wake duration in both cortices, with NREM duration increased within sensorimotor cortex, and REM duration increased within motor cortex. Also, Wake, NREM and REM theta relative amplitude was lower in motor versus sensorimotor cortex in all groups of animals. In sensorimotor cortex bilateral NB lesion increased only REM theta relative amplitude from 1421 days following lesion, and returned to control value 28 days following lesion. In motor cortex both Wake and REM theta relative amplitude transiently increased 14 days following unilateral and bilateral NB lesion, and returned to control values 21 days after lesions. We demonstrated at functional level, for the first time, the topographically specific impact of NB cholinergic cortical afferent system dysregulation on sleep/wake states, REM and Wake EEG theta relative amplitude.