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.