Nutritional recovery does not reverse the activation of brain serotonin synthesis in the ontogenetically malnourished rat

In the present work we confirm that gestational malnutrition affects body and brain composition and results in an activation of the synthesis of the brain neurotransmitter 5-hydroxytryptamine. These results also demonstrate more activity of the rate-limiting enzyme tryptophan hydroxylase in the malnourished fetal and postnatal brain. However, the activity of this enzyme remains increased in the brain of nutritionally recovered animals accompanied by an increase in the synthesis of 5-hydroxytryptamine. We therefore suggest that, in the nutritionally recovered animal, the mechanism of activation of this biosynthetic path in the brain may be not dependent on the increased availability of free l-tryptophan observed in malnourished animals, but might be due to a specific change in the enzyme complex itself. This hypothesis is supported by the fact that plasma free and brain l-tryptophan return to normal in the recovered animal.