Norarenergic and selective serotonergic antidepressants (abbreviated: NaSSAs) are a relatively new class of antidepressants. They are thought to work by blocking presynaptic alpha-2 adrenergic receptors that normally inhibit the release of the neurotransmitters norepinephrine (noradrenaline) and serotonin. This results in increases in both noradrenergic and specific serotonergic transmission.