Effects of C825T polymorphism of the GNB3 gene on availability of dopamine transporter in healthy volunteers--a SPECT study.

Striatal dopaminergic activity is significantly correlated with various cognitive activities, mood regulation, and even metabolic homeostasis, and is modulated by the dopamine transporter (DAT). The availability of DAT could be regulated by presynaptic autoreceptors, which are G-protein coupled receptors; however, whether functional variations in the common downstream signaling molecule, G-protein, could cause individual differences in presynaptic transporter availability remains unclear. To investigate this relationship, the DAT availability in seventy-eight healthy subjects was approximated using single photon emission computed tomography (SPECT) with [(99m)Tc] TRODAT-1, a radio-labeled form of tropan derivative for the selective labeling of DAT. The C825T single nucleotide polymorphism (SNP) (rs5443) of the beta subunit of the G-protein second messenger (GNβ3) gene was genotyped, and analysis of variance showed a significant difference in striatal DAT when referenced to the entire occipital lobe among the three genotypes. Post hoc independent t tests were also performed, and showed that the striatal DAT availability of the CC genotype was higher than that of the other two genotypes. These results indicated that genetic variation in the common downstream signaling molecule of the dopamine autoreceptor could affect the functional status of the striatal dopamine system. These results together with the known role of the GNβ3 gene might provide further evidence to support the common effect of the striatal dopamine system on mood and metabolic regulation.