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Monoamine oxidase B (MAOB) is an enzyme involved in the metabolism of dopamine and converts dopamine to its corresponding carboxylic acid via an aldehyde intermediate.

Depression is associated with reduced levels of monoamines in the brain. Noradrenergic and specific serotonergic antidepressants have a dual mechanism of action that increases the concentration of 5-HT and noradrenaline in the synaptic cleft to within the normal range.

Monoamine oxidase A is an enzyme involved in the metabolism of the monoamines, eg 5-HT and noradrenaline. It converts the monoamines into their corresponding carboxylic acid via an aldehyde intermediate.

The hypothalamic-pituitary-adrenal axis is a feedback loop that includes the hypothalamus, the pituitary and the adrenal glands.

In depression, the hypothalamic-pituitary-adrenal axis is upregulated with a down-regulation of its negative feedback controls. Corticotropin-releasing factor (CRF) is hypersecreted from the hypothalamus and induces the release of adrenocorticotropin hormone (ACTH) from the pituitary.

Dopamine is released from the presynaptic terminal, diffuses over the synaptic cleft and activates Dopaminergic receptors (D1-D5 receptors).