Dopamine release during psychological stress in euthymic bipolar I disorder: a Positron Emission Tomography study with [11C]raclopride

Abstract

BackgroundNeurochemical mechanisms underlying stress induced relapse of mood episodes in Bipolar I Disorder (BD) remain unknown. This study investigated whether euthymic BD patients have a greater dopamine release in ventral striatum, caudate and putamen in response to psychological stress using Positron Emission Tomography (PET) scanning with the radiotracer [11C]raclopride. MethodsEuthymic patients with BD (n = 10) and 10 matched healthy controls underwent two [11C]raclopride PET scans, one during a “stress” and the other in a “no stress” condition separated by at least 24 h. Montreal Imaging Stress Test (MIST) was used to induce stress during stress condition. Participants received an injection of [11C]raclopride over one minute followed by PET scan for 60 min. Participants were assessed for mood symptom severity at baseline, and before and after each scan. The reduction in [11C]raclopride binding in stress condition compared with non-stress rest condition for each subject provided an estimate of dopamine release due to stress. ResultsThere was a significant effect of stress in reducing the [11C]raclopride binding in the ventral striatum, caudate and putamen; however, no significant effects of group or condition x group interaction were found. LimitationsSmall sample size and recruitment of euthymic patients who may be less vulnerable to stress may limit the generalizability of findings. ConclusionsOur findings showed that psychological stress led to dopamine release in the basal ganglia for all participants but the magnitude of dopamine release during a stress task was not different between euthymic BD patients and healthy controls.