Changes in sleep–waking cycle after striatal excitotoxic lesions

Abstract

Huntington's disease (HD) patients show severe diurnal choreic movements, while during slow-wave sleep (SWS) abnormal movements subside. Sleep disturbances in HD, including irregular delta activity and decreases in SWS, have also been reported. Striatal excitotoxic lesions have been shown to induce increased nocturnal spontaneous locomotor activity in rodents. In order to characterize the changes in circadian activity and sleep patterns and their correlation with motor activity after striatal excitotoxic lesions, Sprague–Dawley rats were implanted and lesioned; their locomotor and EEG activities were recorded for either 4 or 24 h during baseline or 7 and 30 days post-lesion. Locomotor activity increased significantly at 7 days post-lesion during the dark phase of the light–dark cycle. In contrast, total time spent in wakefulness (W) increased at 30 days post-lesion during the light phase of the cycle. This increase was at the expense of SWS duration. No disruption of the circadian curves was observed. Increases in the number of W-bouts and decreases in the duration of SWS-bouts were also observed. These results suggest the possible participation of the striatum in the regulation of the sleep–waking cycle, independent of locomotor activity. The increase in W could be due to loss of inhibition of target structures involved in regulation of the sleep–waking cycle.