Age-Related Changes in Passive Avoidance Retention: Modulation with Dietary Choline

Two studies were performed to evaluate the effects of dietary choline manipulation on behavior in mice. Retired breeder mice (8.5 months old) were placed on purified diets that were either deficient in free choline or choline-enriched. After 4.5 months, the mice were trained in a single-trial, passive avoidance task and tested for retention either 24 hours or 5 days later. Their performance was compared with that of mice, of various ages, that were maintained on a control diet. The two salient findings were (i) a dramatic decrease in retention of the task in senescent mice (23 months and older) and (ii) marked behavioral differences between choline-deficient and choline-enriched mice (13 months old). In fact, the choline-enriched mice performed as well as 3-month-old mice, whereas the choline-deficient mice performed as poorly as the senescent mice. In a replication, three groups of retired breeder mice were placed on the same choline-deficient diet; control and enriched groups were given choline through their drinking water. Again, retention of learning was superior in the choline-enriched mice and inferior in the choline-deficient mice. These studies demonstrate that dietary manipulation of choline can significantly alter behavior in ways that are qualitatively and quantitatively similar to those occurring across the life-span of the mouse. Thus certain behavioral changes that occur with age might be modulated through appropriate precursor control.