No evidence for a role of the serotonin 4 receptor in five-factor personality traits: A positron emission tomography brain study

Serotonin (5-HT) brain architecture appears to be implicated in normal personality traits as supported by genetic associations and studies using molecular brain imaging. However, so far, no studies have addressed potential contributions to variation in normal personality traits from in vivo serotonin 4 receptor (5-HT(4)R) brain availability, which has recently become possible to image with Positron Emission Tomography (PET). This is particularly relevant since availability of 5-HT(4)R has been shown to adapt to synaptic levels of 5-HT and thus offers information about serotonergic tone in the healthy brain. In 69 healthy participants (18 females), the associations between personality traits assessed with the five-factor NEO Personality Inventory-Revised (NEO PI-R) and regional cerebral 5-HT(4)R binding in neocortex, amygdala, hippocampus, and anterior cingulate cortex (ACC) were investigated using linear regression models. The associations between each of the five personality traits and a latent variable construct of global 5-HT(4)R levels were also evaluated using latent variable structural equation models. We found no significant associations between the five NEO personality traits and regional 5-HT(4)R binding (all p-values > .17) or the latent construct of global 5-HT(4)R levels (all p-values > .37). Our findings indicate that NEO personality traits and 5-HT(4)R are not related in healthy participants. Under the assumption that global 5-HT(4)R levels index 5-HT tone, our data also suggest that 5-HT tone per se is not directly implicated in normal personality traits.