Monoamines, such as serotonin, dopamine, and norepinephrine, play a crucial role in the regulation of emotion processing and mood. In this study, we investigated how polymorphisms of the serotonin transporter (5-HTT) and catechol-O-methyltransferase (COMT) influence emotion recognition abilities. We recruited 88 female undergraduate students and assessed 5-HTT genotype and the COMT Val158Met polymorphism. The subjects completed two computerized tasks: The Penn Emotion Recognition Test (ER40) and the Penn Emotion Acuity Test (PEAT). For the ER40, we found that s-allele carriers performed significantly worse in the recognition of happy faces, but did better in the recognition of fearful faces, compared with homozygous l-carriers of the 5-HTT gene. Neither 5-HTT nor COMT genotypes influenced the ability to discriminate between different intensities of sadness or happiness on the PEAT. Moreover, there was no significant interaction between the two polymorphisms in their effect on performance on the ER40 or the PEAT. (JINS, 2011, 17, 1014–1020)

ABSTRACT

Up to 60% of OCD patients do not respond to a regular serotonin reuptake inhibitor (SRI) treatment. The purpose of the present study was to determine whether polymorphisms of the serotonin transporter (5-HTT), 5-HT1Dβ, and 5-HT2A receptor genes affect the efficacy of SRI treatment in OCD. Ninety-one outpatients with primary OCD according to DSM-IV criteria consented to the study were randomly assigned a 12-week, double-blind trial to receive dosages titrated upward to 300 mg/day of venlafaxine, or 60 mg/day of paroxetine. Primary efficacy was assessed by the change from baseline on the Yale-Brown obsessive–compulsive scale (Y-BOCS), and response was defined as a ≥25% reduction on the Y-BOCS. All of the paroxetine treated patients, with the G/G genotype of the 5-HT2A polymorphism were responders (χ2 = 8.66, df = 2, p = 0.013). In the venlafaxine treated patients, the majority of responders carried the S/L genotype of the 5-HTTLPR polymorphism (χ2 = 9.71, df = 2, p = 0.008). The small group of patients who both carried the S/L genotype of the 5-HTTLPR polymorphism and the G/G genotype of the 5-HT2A polymorphism responded all to treatment.

The results of this study suggest that the response in paroxetine and in venlafaxine treated OCD patients is associated with the G/G genotype of the 5-HT2A polymorphism and with the S/L genotype of the 5-HTTLPR polymorphism, respectively.

The selective serotonin reuptake inhibitor (SSRI) citalopram (R,S-citalopram) is a racemic compound of two enantiomers. On the basis of in-vitro studies, inhibition of the human serotonin transporter (5-HTT) is achieved by the S-enantiomer (S-citalopram or escitalopram). The aim of the present PET study was to compare 5-HTT occupancy after single equimolar doses (with respect to S-enantiomer) in humans in vivo using R,S-citalopram (20 mg) and S-citalopram (10 mg) using PET and the radioligand [11C]MADAM. The design was a single-dose, double-blind, two-way crossover study in eight healthy male subjects. The 5-HTT binding potential at baseline and after single doses of study drugs was used to calculate 5-HTT occupancy in seven brain regions. Serum concentrations of the study drugs were determined in order to calculate the apparent inhibition constant (Ki,app), a secondary parameter of interest for the comparison. In all brain regions examined, occupancy was numerically higher after treatment with R,S-citalopram [66±19% to 78±17% (mean±s.d.) depending on the region] than after S-citalopram (59±15% to 69±13%; overall comparison: F=14.8, d.f.=1, 90, p<0.001). In line with this the apparent inhibition constant was significantly lower for R,S-citalopram than for S-citalopram (overall comparison: F=6.7, d.f.=1, 90, p<0.05). The small but significant difference in occupancy and Ki,app found between R,S-citalopram and S-citalopram suggests that not only S-citalopram but also R-citalopram to some degree occupies the 5-HTT in the human brain in vivo.