Choline is an essential nutrient that seems to be involved in a wide variety of metabolic reactions and functions, that affect the developing brain. The aim of this study was to: (a)examine the effects of early age choline deficient diet (CDD) administration on the total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), (Na(+),K(+))-ATPase and Mg(2+)-ATPase in the rat brain, (b)investigate the effect of feeding restoration into an equilibrated diet on the above parameters, and (c)study the role of homocysteine (Hcy), L: -phenylalanine (Phe) and L: -alanine (Ala) in certain of the above effects. Male and female Wistar rats were continuously kept off choline (Ch) during their gestational period of life, as well as during the first 6 weeks of their post-gestational life. The animals were sacrificed by decapitation and their whole brains were rapidly removed and homogenated. Their enzyme activities were measured spectrophotometrically. Moreover, in vitro experiments were conducted in order to estimate the effects of Hcy (0.3 mM), Phe (1.2 mM) and/or Ala (1.2 mM) on the above parameters. The administration of CDD led to a statistically significant decrease of the rat brain TAS (-29%, p < 0.001) and to a significant increase of both AChE (+20%, p < 0.001) and (Na(+),K(+))-ATPase (+35%, p < 0.001) activities. Mg(2+)-ATPase activity was found unaltered. Equilibrated diet, administered to early age CDD-treated rats of both sexes for an additional period of 18 weeks, restored the above parameters to control levels. Moreover, the in vitro experiments showed that Hcy could simulate these changes (at least under the examined in vitro conditions), while both Phe and Ala act protectively against the CDD-induced effects on the examined rat brain enzyme activities. The effects of early age CDD-feeding on the examined parameters are proved to be reversible through restoration to equilibrated diet, while our data suggest a role for Hcy (as a causative parameter for the CDD-induced effects) and a possible protective role for Phe and Ala (in reversing the observed CDD-induced effects).