The effect of tryptophan supplementation on autotomy induced by nerve lesions in rats

Rats were fed an artificial diet containing either their normal, or five times their normal, daily requirement of tryptophan for up to five weeks and were tested in an animal model of deafferentation pain, nerve lesion-induced autotomy. In this model one of the hind limbs of the animal was denervated, and the extent to which the animal attacked its denervated paw was assessed. Rats receiving the high-tryptophan diet showed significantly lower levels of autotomy, compared to rats fed the control diet. 5-Hydroxytryptamine and 5-hydroxyindoleacetic acid in the brain and spinal cord were significantly elevated in rats receiving the high-tryptophan diet, indicating that the supplemented diet produced a chronic increase in CNS indoleamine metabolism. Currently there is no accepted pharmacological treatment of deafferentiation pain. Our results suggest that tryptophan should be tested in phantom limb pain and other deafferentation pain syndromes.