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Seasonal Changes in Brain Serotonin Transporter Binding in Short Serotonin Transporter Linked Polymorphic Region-Allele Carriers but Not in Long-Allele Homozygotes

Neurobiology Research Unit, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
Biological psychiatry (Impact Factor: 9.47). 06/2010; 67(11):1033-9. DOI: 10.1016/j.biopsych.2009.11.027
Source: PubMed

ABSTRACT A polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been associated with seasonality both in patients with seasonal affective disorder and in the general population.
We used in vivo molecular imaging to measure cerebral serotonin transporter (5-HTT) binding in 57 healthy Scandinavians and related the outcome to season of the year and to the 5-HTTLPR carrier status.
We found that the number of daylight minutes at the time of scanning correlated negatively with 5-HTT binding in the putamen and the caudate, with a similar tendency in the thalamus, whereas this association was not observed for the midbrain. Furthermore, in the putamen, an anatomic region with relatively dense serotonin innervation, we found a significant gene x daylight effect, such that there was a negative correlation between 5-HTT binding and daylight minutes in carriers of the short 5-HTTLPR allele but not in homozygote carriers of the long allele.
Our findings are in line with S-carriers having an increased response in neural circuits involved in emotional processing to stressful environmental stimuli but here demonstrated as a endophenotype with dynamic changes in serotonin reuptake.

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    • "Comparisons of 5-HTT binding in subjects with different 5-HTTLPR genotypes have been controversial since some studies have not been able to demonstrate any impact of genotype on 5-HTT function in vivo (Murthy et al., 2010; Parsey et al., 2006; Shioe et al., 2003) or post-mortem tissue (Mann et al., 2000). However, such lack of effects of 5- HTTLPR on altered 5-HTT binding can be explained by developmental or environmental rather than direct effects of 5-HTTLPR on adult serotonergic neurotransmission (Gaspar et al., 2003; Kalbitzer et al., 2010; Parsey et al., 2006; Willeit et al., 2008). Moreover, 5-HTTLPR genotypes seem to be affected by epigenetic mechanisms (Alasaari et al., 2012; Kinnally et al., 2010; van IJzendoorn et al., 2010), which could further explain inconclusive findings. "
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