Allelic variation in 5-HTTLPR and the effects of citalopram on the emotional neural network

Brain imaging studies of emotional well-being: a scoping review

This scoping review provides an overview of previous empirical studies that used brain imaging techniques to investigate the neural correlates of emotional well-being (EWB). We compiled evidence on this topic into one accessible and usable document as a foundation for future research into the relationship between EWB and the brain. PRISMA 2020 guidelines were followed. We located relevant articles by searching five electronic databases with 95 studies meeting our inclusion criteria. We explored EWB measures, brain imaging modalities, research designs, populations studied, and approaches that are currently in use to characterize and understand EWB across the literature. Of the key concepts related to EWB, the vast majority of studies investigated positive affect and life satisfaction, followed by sense of meaning, goal pursuit, and quality of life. The majority of studies used functional MRI, followed by EEG and event-related potential-based EEG to study the neural basis of EWB (predominantly experienced affect, affective perception, reward, and emotion regulation). It is notable that positive affect and life satisfaction have been studied significantly more often than the other three aspects of EWB (i.e., sense of meaning, goal pursuit, and quality of life). Our findings suggest that future studies should investigate EWB in more diverse samples, especially in children, individuals with clinical disorders, and individuals from various geographic locations. Future directions and theoretical implications are discussed, including the need for more longitudinal studies with ecologically valid measures that incorporate multi-level approaches allowing researchers to better investigate and evaluate the relationships among behavioral, environmental, and neural factors.

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Behavioral, cortical and autonomic effects of single-dose escitalopram on the induction and regulation of fear and disgust: Comparison with single-session psychological emotion regulation with reappraisal

INTRODUCTION

Adaptive and successful emotion regulation, the ability to flexibly exert voluntary control over emotional experience and the ensuing behavior, is vital for optimal daily functioning and good mental health. In clinical settings, pharmacological and psychological interventions are widely employed to modify pathological emotion processing and ameliorate its deleterious consequences.

METHODS

In this study, we investigated the acute effects of single-dose escitalopram on the induction and regulation of fear and disgust in healthy subjects. Furthermore, we compared these pharmacological effects with psychological emotion regulation that utilized a cognitive strategy with reappraisal. Emotion induction and regulation tasks were performed before and 4 h after ingestion of placebo or 10 mg escitalopram in a randomized, double-blind design. The International Affective Picture System (IAPS) was used as a source of images, with threat-related pictures selected for fear and disease and contamination-related pictures for disgust. Behavioral data, electrodermal activity (EDA), and functional near-infrared spectroscopy (fNIRS) recordings were collected.

RESULTS

Escitalopram significantly reduced emotion intensity for both fear and disgust during emotion induction, albeit with differing electrodermal and hemodynamic activity patterns for the two negative emotions. At rest, i.e., in the absence of emotive stimuli, escitalopram increased sympathetic activity during the fear but not during the disgust experiments. For both fear and disgust, emotion regulation with reappraisal was more effective in reducing emotion intensity compared to pharmacological intervention with escitalopram or placebo.

DISCUSSION

We concluded that emotion regulation with reappraisal and acute administration of escitalopram, but not placebo, reduce emotion intensity for both fear and disgust, with cognitive regulation being significantly more efficient compared to pharmacological regulation under the conditions of this study. Results from the fNIRS and EDA recordings support the concept of differential mechanisms of emotion regulation that could be emotion-specific.

Rediscovering Psilocybin as an Antidepressive Treatment Strategy

There has recently been a renewal of interest in psychedelic research on the use of psilocybin in psychiatric treatment and, in particular, for the treatment of major depressive disorder (MDD). Several state-of-the-art studies have provided new insight into the mechanisms of action of psilocybin and its therapeutic potential. Nevertheless, many questions remain unanswered. With this review, we provide an overview of the current state of research on the potential mechanisms of psilocybin, its antidepressant potential, and the associated risks and adverse effects, to provide an update on a controversial topic discussed in psychopharmacology. A database search was conducted in Medline including articles on psilocybin over the period of the last 20 years. Despite the promising progress in understanding the mechanisms of psilocybin, the exact antidepressive mechanism and the role of the psychedelic experience remain elusive. The studies included in this review found high treatment effect sizes for psilocybin as an antidepressant. However, the results must be regarded as preliminary due to several limitations. Although the current studies observed no severe adverse events, several questions regarding safety and utility remain and must be subject of future research.

Serotonin Transporter (5-HTT) Gene Polymorphisms and Susceptibility to Chronic Periodontitis: A Case-Control Study

Objective: The current study is aimed at exploring the relationship between chronic periodontitis and serotonin transporter (5-HTT) gene polymorphisms (rs6354 and rs12449783) in the Chinese Han population.

Methods: This study included a total of 120 patients with chronic periodontitis and 125 healthy control subjects. The 5-HTT gene (rs6354 and rs12449783) was genotyped using oral mucosal tissue with a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Linkage disequilibrium was examined using Haploview. Genotype and allele frequencies were compared between the cases and controls using a χ² test.

Results: Genotype distribution of the 5-HTT gene polymorphisms rs6354 and rs12449783 in the control group conformed to Hardy–Weinberg equilibrium. The frequency of the AC genotype, the AC + CC genotype and C allele of the 5-HTT rs6354 polymorphism was higher in cases (P < 0.05) vs. the healthy control. The adjusted odds ratio (OR) was 1.910 (95%CI = 1.049–3.476) for the AC genotype, 2.026 (95%CI = 1.115–3.680) for the AC+CC genotype, and 1.875 for the C allele (95%CI = 1.089–3.228. Such an association was particularly strong in women for the AC genotype (OR = 2.167, 95%CI = 1.034–4.542). The genotype and allele frequencies of rs12449783 did not differ between the cases and controls. Haplotype C-C (rs6354-rs12449783) was also more frequent in the cases (OR = 2.372, 95%CI = 1.154–4.875, P = 0.016).

Conclusion: Chronic periodontitis is associated with the 5-HTT gene rs6354 polymorphism, as well as rs6354/rs12449783 interaction.

Insula serotonin 2A receptor binding and gene expression contribute to serotonin transporter polymorphism anxious phenotype in primates

Genetic variation in the serotonin transporter gene (SLC6A4) is associated with vulnerability to affective disorders and pharmacotherapy efficacy. We recently identified sequence polymorphisms in the common marmoset SLC6A4 repeat region (AC/C/G and CT/T/C) associated with individual differences in anxiety-like trait, gene expression, and response to antidepressants. The mechanisms underlying the effects of these polymorphisms are unknown, but a key mediator of serotonin action is the serotonin 2A receptor (5HT_2A). Thus, we correlated 5HT_2A binding potential (BP) and RNA gene expression in 16 SLC6A4 genotyped marmosets with responsivity to 5HT_2A antagonism during the human intruder test of anxiety. Voxel-based analysis and RNA measurements showed a reduction in 5HT_2A BP and gene expression specifically in the right posterior insula of individuals homozygous for the anxiety-related variant AC/C/G. These same marmosets displayed an anxiogenic, dose-dependent response to the human intruder after 5HT_2A pharmacological antagonism, while CT/T/C individuals showed no effect. A voxel-based correlation analysis, independent of SLC6A4 genotype, revealed that 5HT_2A BP in the adjacent right anterior insula and insula proisocortex was negatively correlated with trait anxiety scores. Moreover, 5HT_2A BP in both regions was a good predictor of the size and direction of the acute emotional response to the human intruder threat after 5HT_2A antagonism. Our findings suggest that genetic variation in the SLC6A4 repeat region may contribute to the trait anxious phenotype via neurochemical changes in brain areas implicated in interoceptive and emotional processing, with a critical role for the right insula 5HT_2A in the regulation of affective responses to threat.

Genetic variants in major depressive disorder: From pathophysiology to therapy

In spite of promising preclinical results there is a decreasing number of new registered medications in major depression. The main reason behind this fact is the lack of confirmation in clinical studies for the assumed, and in animals confirmed, therapeutic results. This suggests low predictive value of animal studies for central nervous system disorders. One solution for identifying new possible targets is the application of genetics and genomics, which may pinpoint new targets based on the effect of genetic variants in humans. The present review summarizes such research focusing on depression and its therapy. The inconsistency between most genetic studies in depression suggests, first of all, a significant role of environmental stress. Furthermore, effect of individual genes and polymorphisms is weak, therefore gene x gene interactions or complete biochemical pathways should be analyzed. Even genes encoding target proteins of currently used antidepressants remain non-significant in genome-wide case control investigations suggesting no main effect in depression, but rather an interaction with stress. The few significant genes in GWASs are related to neurogenesis, neuronal synapse, cell contact and DNA transcription and as being nonspecific for depression are difficult to harvest pharmacologically. Most candidate genes in replicable gene x environment interactions, on the other hand, are connected to the regulation of stress and the HPA axis and thus could serve as drug targets for depression subgroups characterized by stress-sensitivity and anxiety while other risk polymorphisms such as those related to prominent cognitive symptoms in depression may help to identify additional subgroups and their distinct treatment. Until these new targets find their way into therapy, the optimization of current medications can be approached by pharmacogenomics, where metabolizing enzyme polymorphisms remain prominent determinants of therapeutic success.

Neural substrates underlying the effects of oxytocin: a quantitative meta-analysis of pharmaco-imaging studies

The hypothalamic peptide oxytocin (OT) is crucial in social adaptation and used to treat emotional and social deficits. Here, we conducted a systematic, quantitative meta-analysis of functional-MRI studies intranasally administering OT (IN-OT) to uncover neural substrates underlying the IN-OT effects and to elucidate differential IN-OT effects between healthy and clinical populations. Meta-analyses were conducted on 66 IN-OT fMRI studies, stratified by psychopathology, valence and sex. IN-OT increased bilateral amygdala, caudate head, and superior temporal activity in healthy individuals and increased dorsal anterior cingulate activity in patients. Moreover, IN-OT decreased amygdala activity in both patients and healthy individuals but did so to a greater degree in patients than healthy individuals. The OT-increased amygdala activity was only found on the negative social and affective processes, whereas the OT-decreased amygdala activity was mainly contributed by contrasts on negative-valenced processes. IN-OT increased parahippocampal activity and decreased amygdala activity during negative socio-affective processing. During positive socio-affective processes, IN-OT increased caudate head activity. This study indicates convergent neural substrates and the underlying neuropsychological mechanisms for IN-OT effects on social and affective processes. The common and different effects of IN-OT on patients and healthy individuals and the modulation of OT effects by valence have critical implications.

Heightened amygdala responsiveness in s-carriers of 5-HTTLPR genetic polymorphism reflects enhanced cortical rather than subcortical inputs: An MEG study

Short allele carriers (S-carriers) of the serotonin transporter gene (5-HTTLPR) show an elevated amygdala response to emotional stimuli relative to long allele carriers (LL-homozygous). However, whether this reflects increased responsiveness of the amygdala generally or interactions between the amygdala and the specific input systems remains unknown. It is argued that the amygdala receives input via a quick subcortical and a slower cortical pathway. If the elevated amygdala response in S-carriers reflects generally increased amygdala responding, then group differences in amygdala should be seen across the amygdala response time course. However, if the difference is a secondary consequence of enhanced amygdala-cortical interactions, then group differences might only be present later in the amygdala response. Using magnetoencephalography (MEG), we found an enhanced amygdala response to fearful expressions starting 40-50 ms poststimulus. However, group differences in the amygdala were only seen 190-200 ms poststimulus, preceded by increased superior temporal sulcus (STS) responses in S-carriers from 130 to 140 ms poststimulus. An enhanced amygdala response to angry expressions started 260-270 ms poststimulus with group differences in the amygdala starting at 160-170 ms poststimulus onset, preceded by increased STS responses in S-carriers from 150 to 160 ms poststimulus. These suggest that enhanced amygdala responses in S-carriers might reflect enhanced STS-amygdala connectivity in S-carriers. Hum Brain Mapp 38:4313-4321, 2017. © 2017 Wiley Periodicals, Inc.

The effects of drugs on human models of emotional processing: an account of antidepressant drug treatment

Human models of emotional processing suggest that the direct effect of successful antidepressant drug treatment may be to modify biases in the processing of emotional information. Negative biases in emotional processing are documented in depression, and single or short-term dosing with conventional antidepressant drugs reverses these biases in depressed patients prior to any subjective change in mood. Antidepressant drug treatments also modulate emotional processing in healthy volunteers, which allows the consideration of the psychological effects of these drugs without the confound of changes in mood. As such, human models of emotional processing may prove to be useful for testing the efficacy of novel treatments and for matching treatments to individual patients or subgroups of patients.

Pharmacogenetics and Imaging-Pharmacogenetics of Antidepressant Response: Towards Translational Strategies

Genetic variation underlies both the response to antidepressant treatment and the occurrence of side effects. Over the past two decades, a number of pharmacogenetic variants, among these the SCL6A4, BDNF, FKBP5, GNB3, GRIK4, and ABCB1 genes, have come to the forefront in this regard. However, small effects sizes, mixed results in independent samples, and conflicting meta-analyses results led to inherent difficulties in the field of pharmacogenetics translating these findings into clinical practice. Nearly all antidepressant pharmacogenetic variants have potentially pleiotropic effects in which they are associated with major depressive disorder, intermediate phenotypes involved in emotional processes, and brain areas affected by antidepressant treatment. The purpose of this article is to provide a comprehensive review of the advances made in the field of pharmacogenetics of antidepressant efficacy and side effects, imaging findings of antidepressant response, and the latest results in the expanding field of imaging-pharmacogenetics studies. We suggest there is mounting evidence that genetic factors exert their impact on treatment response by influencing brain structural and functional changes during antidepressant treatment, and combining neuroimaging and genetic methods may be a more powerful way to detect biological mechanisms of response than either method alone. The most promising imaging-pharmacogenetics findings exist for the SCL6A4 gene, with converging associations with antidepressant response, frontolimbic predictors of affective symptoms, and normalization of frontolimbic activity following antidepressant treatment. More research is required before imaging-pharmacogenetics informed personalized medicine can be applied to antidepressant treatment; nevertheless, inroads have been made towards assessing genetic and neuroanatomical liability and potential clinical application.

Impact of 5-HTTLPR on SSRI serotonin transporter blockade during emotion regulation: A preliminary fMRI study

BACKGROUND

The short ('S') allele of the serotonin transporter (5-HTT)-linked polymorphic region (5-HTTLPR) is associated with increased negative emotion processing bias, and this polymorphism moderates acute effects of selective serotonin reuptake inhibitor (SSRI) treatment. In this preliminary study, we explore the moderating effect of 5-HTTLPR on the impact of the SSRI, escitalopram during emotion regulation of negative emotional stimuli.

METHOD

Thirty-six healthy Caucasian, female participants underwent two fMRI scanning sessions following single dose escitalopram and placebo administration separated by a seven-day washout period according to a double-blind, randomized, placebo-controlled crossover design. Functional connectivity analysis was employed with a left (L) amygdala seed and a right interior frontal gyrus (R IFG) target.

RESULTS

Changes in functional connectivity with emotion regulation and treatment were linearly related to 5-HTTLPR 'L' allele load such that negative R IFG-L amygdala connectivity was increased with an increasing number of 'L' alleles. Therefore, escitalopram may facilitate the effects of reappraisal by enhancing negative functional connectivity, a finding that is greatest in participants homozygous for the 'L' allele and least in those homozygous for the 'S' allele.

LIMITATIONS

Sub-samples of the homozygote 'S/S' and 'L/L' 5-HTTLPR groupings were small. However, the within-subjects nature of the experiment and observing changes at the individual subject level increases our confidence in the findings of the present study.

CONCLUSIONS

The present study elucidates a potential neural mechanism by which antidepressant treatment produces differential treatment outcomes dependent on the 5-HTTLPR polymorphism, providing new and important leads for models of antidepressant action.

Genetic and neural correlates of romantic relationship satisfaction

Romantic relationship satisfaction (RRS) is important for mental/physical health but varies greatly across individuals. To date, we have known little about the biological (genetic and neural) correlates of RRS. We tested the hypothesis that the serotonin transporter promoter polymorphism (5-HTTLPR), the promoter region of the gene SLC6A4 that codes for the serotonin transporter protein, is associated with individuals' RRS. Moreover, we investigated neural activity that mediates 5-HTTLPR association with RRS by scanning short-short (s/s) and long-long (l/l) homozygotes of 5-HTTLPR, using functional MRI, during a Cyberball game that resulted in social exclusion. l/l compared with s/s allele carriers reported higher RRS but lower social interaction anxiety. l/l compared with s/s carriers showed stronger activity in the right ventral prefrontal cortex (RVPFC) and stronger functional connectivity between the dorsal and rostral ACC when being excluded from the Cyberball game. Moreover, the 5-HTTLPR association with RRS was mediated by the RVPFC activity and the 5-HTTLPR association with social interaction anxiety was mediated by both the dorsal-rostral ACC connectivity and RVPFC activity. Our findings suggest that 5-HTTLPR is associated with satisfaction of one's own romantic relationships and this association is mediated by the neural activity in the brain region related to emotion regulation.

Neural correlates of reflection on actual versus ideal self-discrepancy

Subjective feelings of actual/ideal self-discrepancy vary across individuals and influence one's own affective states. However, the neural correlates of actual/ideal self-discrepancy and their genetic individual differences remain unknown. We investigated neural correlates of actual/ideal self-discrepancy and their associations with the serotonin transporter promoter polymorphism (5-HTTLPR) that moderates human affective states during self-reflection. We scanned short/short and long/long allele carriers of 5-HTTLPR, using functional MRI, during reflection on the distance between actual and ideal self in personality traits. We found that larger actual/ideal self-discrepancy was associated with activations in the ventral/dorsal striatum and dorsal medial and lateral prefrontal cortices. Moreover, these brain activities were stronger in short/short than long/long allele carriers and predicted self-report of life satisfaction in short/short carriers but trait depression in long/long carriers. Our findings revealed neural substrates of actual/ideal self-discrepancy and their associations with affective states that are sensitive to individuals' genetic makeup.

Opposing Oxytocin Effects on Intergroup Cooperative Behavior in Intuitive and Reflective Minds

People often favor ingroup over outgroup members when choosing to cooperate. Such ingroup-favored cooperation is promoted by oxytocin-a neuropeptide shown to facilitate social cognition and that has emerged as a pharmacological target for treatments of social functioning deficits. The current study applied a dual-process model to investigate whether and how intuitive and reflective cognitive styles affect the oxytocin-motivated ingroup favoritism in cooperation. We examined oxytocin effects on ingroup favoritism in a double-blind, placebo-controlled between-subjects design where cognitive processing (intuition vs reflection) was experimentally manipulated in healthy Chinese males (n=150). We also supplemented this experimental manipulation with an individual difference analysis by assessing participants' inclination toward intuition or reflection in daily life. Intranasal administration of oxytocin (vs placebo) increased ingroup favoritism among participants primed to be intuitive or those who preferred intuition in daily life. In contrast, oxytocin decreased ingroup favoritism in participants primed to rely on reflective thinking or those who preferred reflective decision-making in daily life. Our results demonstrate that oxytocin has distinct functional roles when different cognitive styles (ie, intuition vs reflection) are promoted during social cooperation in a group situation. Our findings have implications for oxytocin pharmacotherapy of social dysfunction in that whether the effects of oxytocin on social functioning are facilitative, debilitative, or null, depends on an individual's cognitive style.