Effect of a low tryptophan diet on the prolactin responses to the 5-HT2A agonist DOI in the rat

Low tryptophan (TRP) diets decrease brain serotonin (5-HT) content and produce an up-regulation of the function of some but not all 5-HT receptor subtypes. The aim of the present study was to assess the effect of a two week low TRP containing diet on the plasma prolactin (PRL) response to the 5-HT2A receptor agonist 2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI) in the rat. The low TRP diet significantly reduced plasma total TRP as well as brain 5-HT for the two weeks of the study although plasma free TRP was decreased only for the first week of the diet. The PRL response to DOI was significantly increased in the first week of the diet but returned to normal in the second. The results suggest that a low TRP diet produce a transient up-regulation of brain 5-HT2A receptors.