Mechanism of action
The possible analgesic effect of 5-HTP may be accounted for, in part, by its conversion to serotonin. 5-HTP has also been found to increase plasma beta-endorphin and platelet met-enkephalin levels, which may signify a reinforcing effect upon an endogenous analgesic effect.
The mechanism of the possible antidepressant activity of 5-HTP is accounted for by its conversion to the neurotransmitter serotonin which plays a central role in the affective state. Antidepressants may work by either binding to one or more of the family of serotonin 5-HT receptors (5-HT1 - 5-HT7) or by inhibiting the reuptake of serotonin. ...
Pharmacokinetics
Absorption
The immediate precursor in the serotonin synthetic route, 5-hydroxytryptophan (5-HTP), labeled with 11C in the beta position, has become available for studies using positron emission tomography (PET) to examine serotonin formation in human brain. Normalized uptake and intracerebral utilization of tracer amounts of (beta-11C)5-HTP were studied twice in six healthy male volunteers, three of them before and after pharmacological pretreatments ... Pretreatments with benserazide, p-chlorophenylalanine (PCPA), and unlabeled 5-HTP all significantly increased uptake of (beta-11C)5-HTP. The utilization rates in both striatal and frontal cortex were higher than those in the surrounding brain, indicating that PET studies using (beta-11C)5-HTP as a ligand quantitate selective processes in the utilization of 5-HTP.
The efficiency of absorption of 5HTP, as well as its decarboxylation product serotonin, is approximately 47% to 84%. Absorption of 5-HTP occurs by an active transport process. 5-HTP is transported by the portal circulation to the liver where approximately 25% of an administered dose is metabolized ... . 5-HTP that is not metabolized in the liver is transported by the general circulation to the various tissues of the body, including the brain. 5-HTP readily crosses the blood-brain barrier, and is converted to serotonin in brain cells.
Metabolism
5-HTP is transported by the portal circulation to the liver where approximately 25% of an administered dose is metabolized via vitamin B6-dependent L-aromatic amino acid decarboxylase to 5-hydroxytryptamine (5-HT) /serotonin/. 5-HT is subsequently metabolized to 5-hydroxyindole acetaldehyde which is rapidly metabolized to 5-hydroxyindole acetaldehyde which is rapidly metabolized to 5-hydroxyindoleacetic acid (5-HIAA).
5-Hydroxytryptophan is decarboxylated to serotonin (5-hydroxytryptamine or 5-HT) by the enzyme aromatic-L-amino-acid decarboxylase with the help of vitamin B6. This reaction occurs both in nervous tissue and in the liver.
External links
Fact-sheets from PsychonautWiki. Harm-reduction reference only — not medical advice.