Action of SSRIs and NRIs

Illustration showing the action of selective reuptake inhibitor drugs(red) such as the SSRIs and NRIs. These drugs work by selectively blocking neurotransmitters (green) such as serotonin and noradrenaline from being taken back up into the pre-synaptic cell after having been released into the synaptic cleft. This allows more neurotransmitter molecules to remain in the synaptic cleft and increases the likelihood of them binding to receptors (purple) on the post-synaptic cell, thereby strengthening their effect.