Sleep impairments in rats implanted with morphine pellets

Morphine pellets (2 x 75 mg) were subcutaneously implanted in rats and vigi lance states (wakefulness, slow wave sleep and paradoxical sleep) were obse rved during ten days. Significant impairment of each vigilance state distri bution appeared during the first days of morphine dependence. Although waki ng and slow wave sleep were not affected during the last days, paradoxical sleep duration was reduced during dependence. Nevertheless, the sleep-wake circadian rhythm was not abolished. These results suggest that the sleep pr ocess is affected differently in its components (slow wave sleep and parado xical sleep) during morphine dependence.