Effects of amitriptyline on serum glutamate and free tryptophan in rats.

In rats, chronic amitriptyline (14 days, 10 mg/kg, IP) administration resulted in a significant increase in the serum glutamate concentration and concomitant increase in the serum free tryptophan. In contrast, amitriptyline had no effect on the total serum tryptophan or CSF glutamate level. The data confirmed that antidepressant drugs may induce an increase of the serum glutamate concentration in depressive patients.