Circadian distribution of motor-activity in unilaterally 6-hydroxy-dopamine lesioned rats

Sleep abnormalities in idiopathic Parkinson's disease (PD) frequently consist in a reduction of total sleep time and efficacy and subsequent excessive daytime sleepiness. As it remains unclear whether these phenomena are part of the disease itself or result from pharmacological treatment, animal models for investigating the pathophysiology of sleep alterations in PD may add knowledge to this research area. In the present study, we investigate whether changes in circadian motor activity occur in 6-OHDA-lesioning model for PD, and allow a screening for disturbed sleep-waking behaviour. Activity measurements of six male Wistar rats with 6-OHDA-lesions in the medial forebrain bundle and six controls were carried out in two consecutive 12:12 h light-dark (LD) cycles. A computer-based video-analysis system, recording the animals' movement tracks was used. Distance travelled and number of transitions between movement periods and resting periods were determined. Although 6-OHDA-lesioned animals show a reduced locomotor activity compared to non-lesioned rats, the circadian distribution basically remained intact. However, some lesioning effects were more pronounced in the resting phase than in the activity phase, possibly paralleling nocturnal akinesia in PD. In order to further elucidate the described phenomena, it will be necessary to perform studies combining sleep recordings with locomotor activity measurements.