Effects of antidepressant drug treatment and psychotherapy on striatal and thalamic dopamine D2/3 receptors in major depressive disorder studied with [11C]raclopride PET.

Antidepressant drug treatment and psychotherapy are both effective in treating major depression, but there are no published studies comparing the effects of these two treatments on the dopaminergic neurotransmitter system in major depression. We conducted a randomized comparative study on the effects of fluoxetine medication and short-term psychodynamic psychotherapy on striatal and thalamic dopamine D(2/3) receptors in patients with major depression. Duration of the treatment was 4 months, and dopamine D(2/3) receptor binding was quantified before and after treatment as the binding potential (BP (ND)) using [(11)C]raclopride and 3D positron emission tomography. Both treatments were clinically effective in treating major depression, as shown by substantial decreases in symptom ratings. Yet, there were no effects on D(2/3) receptor availability in the ventral striatum or other subdivisions of the striatum. Fluoxetine but not psychotherapy increased [(11)C]raclopride BP (ND) in lateral thalamus (+7.74%, p = 0.002) but this increase was not correlated with clinical improvement. In conclusion, this preliminary study does not support the involvement of ventral dopaminergic neurotransmission in the antidepressant effects of fluoxetine or psychodynamic psychotherapy. The effects of fluoxetine on thalamic dopamine systems need to be further explored.