Changes of behavioral parameters during long-term food restriction in middle-aged Wistar rats.

Food restriction (FR) has a beneficial effect on aging process and exerts a significant effect on the responses of rodents to standard behavioral tasks. The aim of this study was to assess the cumulative influence of FR on the behavioral and biochemical parameters in Wistar rats. Six-month-old rats were subjected to restrictive feeding (50% of the daily food intake, every-other-day feeding regimen) for one month or for six months until ages of 7 and 12months, respectively. We examined the habituation of exploratory movement, amphetamine (AMPH)-induced motor activity, as well as changes in serum corticosterone (CORT) and glucose levels. The results obtained from FR animals were compared with ad libitum (AL)-fed age-matched control rats. Habituation of motor activity was only affected by six months of restrictive feeding. The sensitization of the motor response to AMPH that was observed in animals exposed to FR for one month was not observed in animals that were exposed to the same feeding regimen for six months. Serum CORT was increased and serum glucose was decreased in both FR groups. These results clearly show that despite the similarity of the biochemical changes that were induced by one and six months of FR, the nature of the changes in motor activities in these two groups of animals during habituation and after AMPH treatment was different. Our findings indicate that long-term FR has complex behavioral consequences that need to be carefully evaluated with respect to animal age, duration of FR and severity of the diet.