Feasibility of ASL-based phMRI with a single dose of oral citalopram for repeated assessment of serotonin function.

Assessment of cerebral serotonin (5-HT) function with arterial spin labeling (ASL)-based pharmacological magnetic resonance imaging (phMRI) could be a highly useful tool in clinical psychiatric research. The goal of this study was to verify the reliability of ASL-based phMRI after an oral challenge of a selective serotonin reuptake inhibitor (SSRI) in repeated assessment of cerebral 5-HT function. In a placebo-controlled, within-subject crossover study we investigated the effect of a single oral dose of citalopram on brain cerebral blood flow (CBF) using a pulsed ASL sequence (PASL) in twelve female healthy volunteers. The within-session repeatability of the PASL signal was good for all regions tested (wsCV<15%). Both ROI- and voxel-based analyses revealed small but significant effects of a citalopram challenge on CBF values in 5-HT rich brain regions, among which the frontal gyrus and thalamus. These effects could however not be replicated between sessions, most probably due to the small effect size of the oral citalopram challenge on cerebral blood flow. We therefore conclude that the test-retest reliability of PASL phMRI with an oral citalopram challenge is low, limiting the technique's sensitivity to time-dependent changes and consequently its use as a (clinical) research tool.