Serotonin
Serotonin (5-Hydroxytryptamine, 5-HT)
Synthesis
It is made in the CNS in the raphe nuclei (in the brainstem) also in the GI tract (enterochromaffin cells). It is synthesised from the amino acid L-tryptophan which is obtained from the diet. L-tryptophan can cross the blood brain barrier, whereas serotonin cannot.
Transformation of L-tryptophan into serotonin involves two steps:
Breakdown
It is taken up from the synapse by a monoamine transporter (SERT). Substances that block this transporter include; MDMA, amphetamine, cocaine, TCA's, and of course SSRI's. It is broken down by MAO and then oddly enough aldehyde dehydogenase to 5-Hydroxyindoleacetic acid (5-HIAA).
Synthesis
It is made in the CNS in the raphe nuclei (in the brainstem) also in the GI tract (enterochromaffin cells). It is synthesised from the amino acid L-tryptophan which is obtained from the diet. L-tryptophan can cross the blood brain barrier, whereas serotonin cannot.
Transformation of L-tryptophan into serotonin involves two steps:
- Hydroxylation to 5-hydroxytryptophan catalysed by tryptophan hydroxylase
- Followed by decarboxylation of 5-hydroxytryptophan to serotonin (5-hydroxytryptamine) by L-aromatic amino acid decarboxylase
Breakdown
It is taken up from the synapse by a monoamine transporter (SERT). Substances that block this transporter include; MDMA, amphetamine, cocaine, TCA's, and of course SSRI's. It is broken down by MAO and then oddly enough aldehyde dehydogenase to 5-Hydroxyindoleacetic acid (5-HIAA).
