A preliminary study of dopamine transporter binding in bipolar and unipolar depressed patients and healthy controls

We examined striatal dopamine transporter (DAT) binding in bipolar and unipolar depressed patients and compared these values to those obtained from healthy control subjects using the selective DAT radioligand [(99m)Tc]TRODAT-1 and single photon emission computed tomography imaging. We hypothesized that DAT levels might be higher in bipolar versus unipolar patients.

[(99m)Tc]TRODAT-1 scans were acquired from 5 bipolar and 10 unipolar patients and from 46 healthy controls. Distribution volume ratio (DVR) of [(99m)Tc]TRODAT-1 binding affinity was calculated for regions of interest in the striatum.

Bipolar patients had greater DVR values compared to controls in the right posterior putamen (p = 0.001) and in the left caudate region (p = 0.007). Bipolar patients had modestly lower DAT binding in all brain regions examined, and a significantly lower DVR in the right caudate region compared to unipolar patients (p = 0.05).

These data suggest that striatal DAT density may be increased in bipolar and unipolar depressed patients compared to controls, and that bipolar and unipolar depressed patients may have a different pattern of striatal DAT binding.