Serotonin (5-HT) is an indolamine neurotransmitter synthesised from tryptophan, an essential amino acid found in the diet that is preferentially taken up by serotonergic neurons. The rate-limiting step in its formation involves tryptophan hydroxylase. 5-HT is catabolised by monoamine oxidase to form 5-hydroxyindolacetic acid.
·The rate-limiting step is between L-tyrosine and L-DOPA (tyrosine hydroxylase). ·The main break down products are MHPG, HVA and VMA. ·MAO acts mainly intraneuronally. ·COMT acts at the synaptic cleft.
1. Pharmacological Targets in
Adapted from Kandel et al., eds. Principles of Neural Science.
Norwalk, CT: Appleton & Lange; 1991:854.
and Cognitive Symptoms
Dopaminergic Pathways in the Brain