Altered dopaminergic function and negative symptoms in drug-free patients with schizophrenia. [¹²³I]-iodobenzamide SPECT study

Background: Previous in vivo studies of schizophrenia with dopamine D₂ receptor radioligands have yielded contradictory results. No prior study has used multiple scans to examine within-subject clinical change. Method: Twenty-one patients were studied with [¹²³I]-iodobenzamide single photon emission computed tomography about two weeks after neuroleptic withdrawal. Thirteen of the 21 completed a second scan about four weeks after neuroleptic withdrawal. Sixteen controls were scanned for comparison. Results: There was no significant difference between groups in [¹²³I]-iodobenzamide uptake at either scanning session. No significant correlations with demographic variables (age, illness duration, drug-free period), or clinical ratings (positive and negative symptoms, movement disorder) were observed at either scanning session. There was a significant correlation between change in [¹²³I]-iodobenzamide uptake and change in negative symptom ratings for the subjects who underwent two scans (r = 0.72, P < 0.05). Conclusions: Worsening of negative symptoms may be associated with increased availability of striatal D₂ receptors, perhaps because of decreased concentrations of endogenous dopamine.