In vivo measurements of brain trapping of C-11-labelled alpha-methyl-L-tryptophan during acute changes in mood states

Background: Little is known about the specific contribution of serotonin (5-HT) to the neurobiology of emotion and mood in healthy people. In an exploratory study, we sought to investigate the effect of rapid and sustained changes of emotional state on the trapping of 11C-labelled α -methyl-L-tryptophan (11C-α Mtrp) used as a proxy of 5-HT synthesis, using positron emission tomography (PET). Method: In a within-subject repeated-measure design, participants recalled autobiographical memories to self-induce sadness, happiness and a neutral emotional state during scanning to measure brain trapping of 11C-α Mtrp. Three separate scan acquisitions, counterbalanced for order across subjects, took place at the McConnell Brain Imaging Center, Montréal. Results:Whole brain analysis revealed positive and negative correlations between experienced levels of emotions and 11C-α Mtrp trapping in the right anterior cingulate cortex. Conclusion:These findings point to a mechanism whereby state-related changes in a proxy of 5-HT synthesis underscore aspects of the self-regulation of normal mood.