Ambulatory activity and dopamine turnover in streptozotocin-induced diabetic rats

This study was undertaken to investigate the changes of ambulatory activity and dopamine turnover (DOPAC/DA ratio) in streptozotocin (STZ 60 mg/kg ip)-induced diabetic rats employing the Gunma University-type special apparatus. A significant decrease in ambulatory activity was observed during the dark phase but not during the light phase 1 month after administration of STZ. Moreover, through the precise observation during light phase, we have found out that a significant decrease compared to control periods was observed during 9:00 to 12:00, whereas increase during 12:00 to 15:00 and 5:00 to 18:00 in the diabetic rats. In addition, a significant decrease in dopamine turnover compared to control rats was seen during dark phase (20:00), when significantly decreased ambulation was observed in the diabetic rats compared to control rats. However, no difference in dopamine turnover was observed during light phase (8:00), when ambulation was not significantly different from both groups. These results may suggest that fluctuation in dopamine turnover may be closely related to the ambulatory activity in STZ-induced diabetic rats.