Studies in animals suggest that the 5-HT 4 receptor (5-HT4) shows a monotonic inverse association with long-term changes in serotonin levels indicating that it may be a useful measure for identifying differences in serotonergic neurotransmission. In 47 healthy adults we evaluated the association between 5-HTTLPR status and in vivo 5-HT4 receptor binding assessed with [11C]SB207145 positron emission tomography (PET).
We observed a significant association within the neocortex where [11C]SB207145 binding was 9 % lower in S carriers compared to LL homozygotes. We did not find evidence for an effect of season or a season-by-5-HTTLPR interaction effect on regional [11C]SB207145 binding.
Our findings are consistent with a model wherein the 5-HTTLPR S allele is associated with relatively increased serotonin levels. These findings provide novel evidence supporting an effect of 5-HTTLPR status on serotonergic neurotransmission in adult humans. There were no indications of seasonal effects on serotonergic neurotransmission.