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

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. 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. 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. 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.