Striatal dopamine D2/3 receptor availability in treatment resistant depression

Area of Science:

• Neuroscience
• Psychiatry
• Radiology

Background:

• Dopamine agonists improve depressive symptoms in treatment-resistant depression (TRD), suggesting abnormal dopaminergic neurotransmission.
• Previous research has not investigated striatal dopamine D(2/3) receptor (D2/3R) binding in TRD patients.

Purpose of the Study:

• To investigate striatal D2/3R binding in severe TRD patients using [(123)I]IBZM SPECT.
• To compare D2/3R availability between TRD patients, TRD patients on antipsychotics (TRD AP), and healthy controls.

Main Methods:

• Utilized [(123)I]IBZM single photon emission computed tomography (SPECT) imaging.
• Included 6 severe TRD patients, 11 TRD AP patients, and 15 matched healthy controls.

Main Results:

• No significant difference in striatal D2/3R availability was observed between TRD patients and healthy controls (p = 0.75).
• TRD AP group showed significantly decreased D2/3R availability compared to TRD patients and controls (p<0.001), indicating antipsychotic occupancy.
• No clinical symptom differences were found between TRD AP and TRD patients, despite D2/3R occupancy.

Conclusions:

• This preliminary study does not support the hypothesis of altered dopaminergic transmission in severe TRD patients.
• Severe TRD patients do not appear to have large differences in striatal D2/3R availability.
• Atypical antipsychotics showed no clinical benefit in severe TRD patients, even with significant D2/3R occupancy.