The central-nervous-system toxicity of long-term oral administration of L-tryptophan to porto-caval-shunted rats.

In a previous paper we have reported that the oral long-term administration of 200 mg/kd of L-tryptophan to rats with a porto-caval shunt causes significant loss of body weight, muscular hypertonicity and aggressivity, as well as marked alteration of the liver structure. We now report that tryptophan administered at the same dosage for the same length of time also induces significant alteration of the central nervous system. These results further demonstrate that high plasma levels of tryptophan are quite well tolerated by control animals but are quite toxic to rats with a porto-caval shunt. We also claim that the brain alterations observed in such animals are not secondary to liver dysfunction but to high levels of plasma tryptophan per se.