EFFECTS OF THE SUBACUTE ADMINISTRATION OF NEFIRACETAM ON ABNORMAL-BEHAVIOR IN AGED RATS

We investigated the effects of nefiracetam on learning and memory by t he Morris water maze task and water-finding test, and on emotional beh avior by forced swimming, hole-board and open-held tests in old male K bl Wistar rats aged 90 and 108 weeks. In the water maze task, the acqu isition of the task in aged rats was slower than that in young rats. S ubacute administration of nefiracetam (1 and 3 mg/kg daily) for 24 day s tended to shorten the goal latency to escape onto the platform in a dose-dependent manner in the retention test, conducted 24 days after a cquisition training. Nefiracetam (1 mg/kg) administration for 49 days decreased the duration of immobility in aged rats in the forced swimmi ng test. Locomotor activity in young rats during the dark period was s ignificantly higher than that during the light period, while there was no difference in locomotor activity between the light and dark period s in aged rats, suggesting that locomotor activity during the dark per iod and nocturnal habits may be impaired in aged rats. Subacute admini stration of nefiracetam for 14 days significantly increased the locomo tor activity during the dark, but not light, period in a dose-dependen t manner. In addition, nefiracetam given for 38 days, significantly sh ortened the increased time elapsed before animals started exploring th e environment in aged rats compared with young rats in the water findi ng tests. These findings suggest that nefiracetam may improve the impa ired nocturnal habits and some of emotional behavior in aged rats.