Differential effect of acetyl-l-carnitine on open field behavior in young and old rats

Acetyl-l-carnitine (ALCAR) exerts antiaging effects with regard to various physiological and neurochemical measures in rats. In this study we evaluated the effect of a chronic treatment with ALCAR (6 weeks, 50 mg/kg/day) on the open field behavior of 5-month-old and 26-month-old male Wistar rats. Old rats defecated more, made fewer crossings, and spent more time in the corner squares. However, it is difficult to interpret these findings in terms of an increase in emotional reactivity with age because locomotor performance generally has been found to be impaired in old rats. Consequently, treatment effects were analysed within age groups. ALCAR had no effect in young rats, but the old ALCAR-treated rats ambulated less and spent more time in the corner squares than the old control rats. We have interpreted this in terms of an enhanced emotional reactivity of old ALCAR-treated rats.