(a) A highly simplified schema for the proposed mechanism of action of selective serotonin reuptake inhibitors (SSRIs). In depression, there is thought to be a relative 5-HT deficiency, and upregulation of 5-HT receptors. The net effect is abnormal signalling and functioning of the postsynaptic neuron. SSRIs block the 5-HT transporter, and increase 5-HT in the synapse. The antidepressant effect ..