Wellbutrin (bupropion) is an atypical antidepressant that is primarily classified as a dopamine and norepinephrine reuptake inhibitor (DNRI). Unlike most other antidepressants, it does not work primarily by increasing the levels of serotonin in the brain.
Bupropion inhibits the reuptake of dopamine and norepinephrine by the presynaptic neurons, thereby increasing the concentration of these neurotransmitters in the synaptic cleft between neurons. This leads to prolonged activation of postsynaptic dopamine and norepinephrine receptors and is thought to underlie the therapeutic effects of the medication.
Bupropion may also have other mechanisms of action that are not yet fully understood. For example, it has been shown to modulate the activity of certain ion channels in the brain, including the nicotinic acetylcholine receptor and the voltage-gated sodium channel, which may contribute to its therapeutic effects.
Overall, bupropion is thought to work by increasing the levels of dopamine and norepinephrine in the brain, which can help to improve mood, increase motivation, and reduce fatigue. It is commonly used to treat depression, seasonal affective disorder, and to aid in smoking cessation.