Inhibition of diet-restriction-induced behavioral deficits by tryptophan administration in rats.

Diet has a great impact on brain health and function. It plays an important role to improve and control a number of psychiatric disorders such as depression, anxiety, hyperactivity and behavioral impulsivity. Anorexia Nervosa (AN) is one of the psychiatric disorder which is associated with diet. In AN, patients show extreme dieting, weight loss, hyperactivity, depression/anxiety, self-control and behavioral impulsivity. Previous studies showed that during diet restriction, tryptophan decreases serotonin (5-hydroxytryptamine; 5-HT) metabolism in the brain due to its less availability and contributes psychiatric problems associated with AN. The present study is designed to investigate the effects of tryptophan administration on 5-HT metabolism in diet-restricted rats. Tryptophan at a dose of 50 or 100mg/kg was given orally to respective freely fed (FF) or diet restricted (DR) animals daily for five weeks. Behavioral activities were also monitored weekly. The results show significant effect (p<0.05) on behavior in activity box, open field and in light/dark transition test by tryptophan administration in diet-restricted rats. This may be associated with the increased in serum tryptophan and brain 5-HT metabolism. Therefore, it is concluded that diet-restriction-induced behavioral changes might be reverted back with the administration of tryptophan and may be helpful to improve psychological problems in AN.