Reduction in brain serotonin synthesis rate in streptozotocin-diabetic rats.

The rate of serotonin synthesis in brain was determined in streptozotocin-diabetic and normal rats using two methods. Both the rate of 5-hydroxytryptophan accumulation after aromatic amino acid decarboxylase inhibition, and the decline rate of 5-hydroxyindole acetic acid after pargyline treatment were significantly reduced in diabetic rats. The reduced rate of synthesis may be a direct result of significantly lowered brain tryptophan levels in diabetic rats.