RESUMO
BACKGROUND: Neurochemical 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. METHODS: Euthymic 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. RESULTS: There 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. LIMITATIONS: Small sample size and recruitment of euthymic patients who may be less vulnerable to stress may limit the generalizability of findings. CONCLUSIONS: Our 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.