The effect of L-tryptophan on conditioned reflex learning and behavior in rats with experimental pathology of the thyroid gland.

The effects of L-tryptophan on conditioned reflex learning and behavior were studied in male rats with deficient and excess thyroid hormones levels. The learning process was studied using a model consisting of a conditioned active avoidance response; animal behavior was assessed in an open field test. These studies showed that in conditions of thyroid hormone deficiency. L-tryptophan had positive effects on the acquisition and reproduction of the active avoidance reflex, restoring the ability of the animals to learn actively; L-tryptophan increased investigative activity in the open field test. In conditions of increased thyroid hormone levels, L-tryptophan reversed the mild stimulating effects of thyroid hormones on the processes of developing and performing the active avoidance habit, and increased investigative activity, but decreased the amount of grooming.