title: An unexpected effect of L-5 hydroxytryptophan-ethyl-ester combined with a peripheral decarboxylase inhibitor on human serum prolactin.
abstract: While the 5-HT precursors tryptophan and 1-5-HTP cause an increase in serum prolactin concentration, a combination of 1-5-HTP with a peripheral decarboxylase inhibitor was found to reduce the serum prolactin concentration. This combination seemed to behave like a DA agonist. This effect is not produced by the decarboxylase inhibitor per se. A possible explanation is that 5-HTP is converted to 5-HT in CA-ergic neurons, that 5-HT supersedes the CA from the stores, and that some of the CA reach the synaptic cleft and stimulate CA receptors. Another possible explanation is that 5-HTP decarboxylase is centrally inhibited as well, and that an effect of 5-HTP itself is involved here. In view of the observations made it is doubtful whether the therapeutic effect of 5-HTP combined with a peripheral decarboxylase inhibitor in depressions and myoclonus can in fact be atributed to activation of central serotonergic systems.
mesh_terms: D006916:5-Hydroxytryptophan / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000328:Adult; D001545:Benserazide / Q000008:administration & dosage / Q000494:pharmacology*; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors*; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology*; D006897:Hydroxyindoleacetic Acid / Q000097:blood; D007263:Infusions, Parenteral; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000097:blood*; D012701:Serotonin / Q000097:blood
chemical_list: D006834:Hydrazines; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D001545:Benserazide; D011388:Prolactin; D006916:5-Hydroxytryptophan; D002262:Carboxy-Lyases