Neurotransmitters and Their Role in Depression

Depression has been noted in 10 to 15% of all patients who take reserpine for the treatment of hypertension. When used for the treatment of tuberculosis, isoniazid brings about mood elevation. Reserpine was found to diminish the levels of brain neurotransmitters such as dopamine, serotonin, and norepinephrine, whereas isoniazid, through its monoamine oxidase inhibitory actions, augments the levels of these substances. It was thus theorized that too much of one or more of these neurotransmitters might be associated with states of hypomania or mania, whereas too little would correlate with depression. 

GABA inhibits the action of the locus ceruleus and this is mediated by the GABAa receptor-chloride channel system. The plasma and cerebrospinal fluid levels of GABA are low, and progabide, a GABAa receptor agonist, has antidepressant properties. 

Drugs used in the treatment of depression are referred to as thymoleptics, thymoanaleptics, psychoanaleptics, psychic energizers, and antidepressants. 

The three-ring nucleus characteristic of the dibenzapine derivatives has given rise to their name of tricyclics or heterocyclics. They resemble the phenothiazine derivatives such as chlorpromazine in structure and function. 

Similar to the phenothiazine derivatives (e.g., chlorpromazine), tricyclic antidepressants (e.g., imipramine) may  

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