Results of preclinical and clinical studies implicate that, in addition to
serotonin and norepinephrin, dopaminergic mechanisms play a role in the pathogenesis and treatment of depression. Newer
antidepressants such as
bupropion,
sertraline, and
venlafaxine act as partial inhibitors of presynaptic
dopamine reuptake. Experimental studies show that
dopaminergic effects contribute to the development of anxiety, depression, and
anhedonia. These studies revealed, among the new nonergot
dopamine agonists,
anxiolytic properties for
ropinirole and
anxiolytic, antidepressive, and antianhedonic effects of
pramipexole which seem to relate to its specific action on D(2) and D(3) receptors in the mesolimbic system and prefrontal cortex. In addition,
affective disorders may be associated with impairments of neuronal plasticity, and
pramipexole seems to exert neurotrophic properties. Controlled and open studies in depressed patients with
Parkinson's disease show
therapeutic effects of
dopamine agonists on motor deficits,
anhedonia, and depression. Various
dopamine agonists have been tested in open studies in patients with depression and may add to the spectrum of treatment options in
mood disorders. Recently published placebo-controlled trials in small patient groups implicate that
pramipexole is effective as additional treatment to mood stabilizers in I and II
bipolar depression.