| Abstract: | Hypoactivity was observed in the open field performance of 28 rats fed a diet containing 3% excess L-phenylalanine and .12% p-chlorophenylalanine between 21–51 days of age (PKU group) compared to both pair-fed and ad lib control groups. Open field testing was conducted 4–11 days following termination of the phenylalanine, p-chlorophenylalanine diet. While on the diet serum phenylalanine levels of the PKU group ranged between 16.6–38.0 mg%. Twenty-four to 48 hours following termination of the PKU diet serum phenylalanine levels had returned to normal (i.e., 2–10 days prior to open field testing). The reduced open field activity of the PKU group is not attributable to differences in food consumption or weight at the time of testing. Hypoactivity is consistent with previous investigations administering chronic doses of phenylalanine, but employing different induction techniques, treatment durations, and activity measures. |
