effects of bilateral lesion of the locus coeruleus on the sleep-wake cycle in the rat

introduction: noradrenergic cells in lc participate in the process of cortical activation and behavioral arousal. the evidence suggests that locus ceoruleus (lc) plays an important role in the sleep-wake cycle. the aim of this study was stereological estimation of cavity caused by lesion and assessment of sleep stages after bilateral lesion of the lc. materials and methods: male wistar rats weighting 250-275 gr were divided into four groups (control: n=6, sham: n=6, lesion1: n=6 and lesion2: n=6). 6 hydroxydopamine (6 ohda) (2μg/0.5μl and 4μg/1μl) was sterotaxically injected bilaterally into lc to produced lesion. for sleep recording 3 eeg and 2 emg electrodes were implanted respectively in the skull and dorsal neck muscle. recordings were taken before and 7, 21 and 42 days after lesion. after 7 weeks, rats first were anesthetized and then their brains were removed and cut in 7 μm serial sections and stained with cresyl violet. the volume of lc and the lesion induced cavity were evaluated through the stereological technique. results: lesion - induced cavity volume (0.5 μl) was restricted to lc, whereas another group (1 μl), total lc and structures adjacent to the lc were also damaged. a significant decrease was seen in non-rapid eye movement (nrem) and paradoxical sleep (ps) stages and a significant increase was seen in duration of wake and paradoxical sleep without atonia (ps-a) in lesion group in comparison with control and sham groups. conclusion: the results of this study demonstrate 2μg/0.5μl 6-ohda is suitable dose for lc lesion and bilateral lesion of lc causing disrupt wake, nrem ,ps and also produce the ps-a.