Noradrenergic and specific serotonergic antidepressants (NaSSAs) are a class of psychiatric drugs used primarily as antidepressants. They act by antagonizing the a₂-adrenergic receptor and certain serotonin receptors such as 5-HT_2A and 5-HT_2C, but also 5-HT₃, 5-HT₆, and/or 5-HT₇ in some cases. By blocking a₂-adrenergic autoreceptors and heteroreceptors, NaSSAs enhance adrenergic and serotonergic neurotransmission in the brain involved in mood regulation, notably 5-HT_1A-mediated transmission. In addition, due to their blockade of certain serotonin receptors, serotonergic neurotransmission is not facilitated in unwanted areas, which prevents the incidence of many side effects often associated with selective serotonin reuptake inhibitor (SSRI) antidepressants; hence, in part, the "specific serotonergic" label of NaSSAs.