The Effects of Methionine-Enriched and Vitamins (Folate, Pyridoxine and Cobalamine)-Deficient Diet on Exploratory Activity in Rats - A Brief Report

The aim of this study was to evaluate the impact of increased homocysteine levels induced by methionine nutritional overload (twice as standard) and deficiency of the vitamins folate, pyridoxine and cobalamine, which plays an important role in homocysteine metabolism in anxiety-related behaviour, expressed by means of exploratory activity in rats. Twenty-three male Wistar albino rats (4 weeks old, 100±15 g body weight) were divided into three groups: control (n=8), methionine-enriched (Meth+, 7.7 g of methionine/kg chow, n=7) and methionine-enriched vitamin-deficient (Meth+Vit-, 7.7 g of methionine/ kg chow, deficient in folate, pyridoxine and cobalamine - 0.08, 0.01 and 0.01 mg/kg, n=8). All animals had free access to food and water for 30 days. Behavioural testing was performed using the elevated plus maze (EPM) test. Standard parameters for vertical exploratory activity, the number of rearings and the number of head-dippings, as well as the total exploratory activity (summarizing overall exploratory activity in the EPM) were significantly reduced following 30 days of methionine nutritional overload (p<0.05, p<0.05 and p<0.01, respectively). A methionine-enriched diet coupled with a reduction in some B vitamins resulted in a more pronounced decline in exploratory drive observed in the EPM test compared to the control (p<0.01). The decline in total exploratory activity associated with vitamin deficiency was significant compared to the Meth+ group (p<0.05). The results of this study highlight the important role of homocysteine in the modulation of exploratory activity in rats. Decreased exploratory drive induced by both a methionine-enriched and vitamin-deficient diet could be attributed to an anxiogenic effect of hyperhomocysteinemia.