Neuromodulation of the prefrontal cortex during sleep: a microdialysis study in rats

To test the hypothesis that biogenic amines of the prefrontal cortex are in volved in state-dependent cortical and behavioural activation, changes in e xtracellular levels of serotonin (5-HT), dopamine (DA), and noradrenaline ( NA) were determined during the sleep-wake cycle in freely moving rats using microdialysis probes with parallel EEG recording. Serotonin gradually incr eased up to 450% during wakefulness (W) as compared to slow wave sleep (SWS ), before decreasing toward stable levels during the next episode of SWS. D opamine and its metabolite homovanillic acid (HVA) were reduced during W as compared to SWS. Although contradictory with the generally admitted enhanc ement of DA activity related to vigilance, this may be due to the particula r role of DA neurons in the prefrontal cortex However, DA and HVA showed dr amatic changes announcing the transition between SWS and W. During paradoxi cal sleep (PS), DA and 5-HT showed complex changes, the direction of which depended on whether PS was followed by SWS or W. Biogenic amines of the pre frontal cortex are probably involved in cortical and behavioural activation . NeuroReport 11:1619-1624 (C) 2000 Lippincott Williams & Wilkins.