Here is a simplified overview of neurotransmitters in the brain that are relevant to antidepressants. Serotonin, norepinephrine, dopamine, and histamine are referred to as monoamine neurotransmitters because they contain a single amine group (—NH2). The monoamine neurotransmitters serotonin and dopamine are implicated in most psychiatric disorders.
Anticonvulsants, barbiturates, benzodiazepines, and hypnotics predominantly enhance GABA-ergic activity. Antidepressants predominantly enhance serotonergic activity. Some antidepressants also have stimulating properties by enhancing the effects of norepinephrine and/or dopamine.