Dopaminergic Activity in Antipsychotic-Naïve Patients Assessed With Positron Emission Tomography Before and After Partial Dopamine D Receptor Agonist Treatment: Association With Psychotic Symptoms and Treatment Response.

Background: Dopamine activity has been associated with the response to antipsychotic treatment. Our study used a four-parameter model to test the association between the striatal decarboxylation rate of F-DOPA to F-dopamine (k) and the effect of treatment on psychotic symptoms in antipsychotic-naïve patients with first-episode psychosis. We further explored the effect of treatment with a partial dopamine D receptor agonist (aripiprazole) on k and dopamine synthesis capacity (DSC) determined by the four-parameter model and by the conventional tissue reference method.

Methods: Sixty-two individuals (31 patients and 31 control subjects) underwent F-DOPA positron emission tomography at baseline, and 15 patients were re-examined after 6 weeks. Clinical re-examinations were completed after 6 weeks (n = 28) and 6 months (n = 15). Symptoms were evaluated with the Positive and Negative Syndrome Scale.

Results: High baseline decarboxylation rates (k) were associated with more positive symptoms at baseline (p < .001) and with symptom improvement after 6 weeks (p = .006). Subregion analyses showed that baseline k for the putamen (p = .003) and nucleus accumbens (p = .013) and DSC values for the nucleus accumbens (p = .003) were associated with psychotic symptoms. The tissue reference method yielded no associations between DSC and symptoms or symptom improvement. Neither method revealed any effects of group or treatment on average magnitudes of k or DSC, whereas changes in dopamine synthesis were correlated with higher baseline values, implying a potential effect of treatment.

Conclusions: Striatal decarboxylation rate at baseline was associated with psychotic symptoms and treatment response. The strong association between k and treatment effect potentially implicate on new treatment strategies.