Α-Methyl-5-hydroxytryptophan

α-Methyl-5-hydroxytryptophan (α-Me-5-HTP) is a synthetic tryptamine derivative, an artificial amino acid, and a prodrug of α-methylserotonin. It is the α-methylated derivative of 5-hydroxytryptophan (5-HTP), while αMS is the α-methylated analogue of serotonin. Along with α-methyltryptophan (α-MTP), α-Me-5-HTP has been suggested for potential therapeutic use in the treatment of conditions thought by some authors to be related to serotonin deficiency, such as depression.

αMS is a non-selective serotonin receptor agonist, including of the serotonin 5-HT2 receptors, and has been described as a "substitute neurotransmitter" of serotonin. However, whereas αMS itself is too hydrophilic to efficiently cross the blood–brain barrier, thus being peripherally selective, α-MTP and α-Me-5-HTP are able to cross the blood–brain barrier and, following transformation, deliver αMS into the brain. Besides αMS, α-methylmelatonin can be formed in small amounts from α-Me-5-HTP.

In addition to their serotonergic activity, α-Me-5-HTP and αMS have been found to act as norepinephrine releasing agents similarly to α-methylphenylalanine and to other α-alkylated tryptamines. Moreover, α-Me-5-HTP is also a tyrosine hydroxylase inhibitor similarly to α-methyltyrosine, as well as an aromatic L-amino acid decarboxylase (AAAD) inhibitor, and has been found to deplete levels of brain norepinephrine in animals, although not levels of brain dopamine. Because of these actions, α-Me-5-HTP shows antihypertensive effects and reduces locomotor activity in animals.