Mechanism of action of selective serotonin
reuptake inhibitor (SSRI)

Following a neuronal impulse, conduction neurotransmitters are released into the synaptic cleft, and they bind receptors on the postsynaptic membrane. The process is terminated either by degradation (in this particular case by monoaminoxidase (MAO) or catechol-O-methyltransferase (COMT)) or reuptake of the neurotransmitters by the corresponding receptors on the presynaptic membrane. SSRIs (selective serotonin reuptake inhibitors) bind to post-synaptic 5-HT receptors and function as competitive antagonists that increase the levels of serotonin in the synaptic cleft and thus, enhance stimulus conduction. This effect is used in the synthesis of new psychotic compounds for the treatment of depression, anxiety disorders, and some personality disorders.