Description: Antidepressants are the first line of treatment for major depressive disorder (MDD). Antidepressants work by blocking the reuptake of serotonin into presynaptic neurons. Serotonin is released when neurons fire at synapses, and it then binds to receptors on the postsynaptic neuron. Inhibition of its reuptake prevents the recycled serotonin from binding to these receptors again.