Acetylcholine release, EEG spectral analysis, sleep staging and body temperature studies: A multiparametric approach on freely moving rats

We present a neurochemical, electrophysiological and physiological study on freely moving rats. During 3 days, we have simultaneously monitored acetylcholine (ACh) release in the hippocampus using the microdialysis technique, electroencephalogram (EEG), electromyogram (EMG) and subcutaneous temperature. A spectral analysis of EEG was performed and sleep stages were determined. Energy ratio in the delta (0–4 Hz), slow theta (4–6.5 Hz) and fast theta (6.5–9 Hz) band was calculated. Sleep stages were quantified using an automatic staging method.The circadian cycle of these parameters was observed. Waking, body temperature and ACh release presented synchronized cycles with close acrophases.The relationship between the central cholinergic system and the other parameters is discussed. The influence of handling on the measured parameters, as well as possible artifacts linked to the use of neostigmine in the microdialysis method are considered. Attention was focused on the cholinergic control of EEG theta rhythms.