No evidence for blocking the return of fear by disrupting reconsolidation prior to extinction learning.

Fear extinction is a central model for the treatment of anxiety disorders. Initial research has reported that the single presentation of a conditioned stimulus prior to extinction learning can permanently block the return of fear. However, only few studies have explored this issue and could not always replicate the findings. The present study examined human fear extinction using a four-day design. On the first day, two neutral stimuli were paired with electrical stimulation (UCS), while a third stimulus (CS-) was not. Twenty-four hours later, one conditioned stimulus (CS+rem) and the CS- were reminded once, 10 min before extinction learning, while the other conditioned stimulus (CS+non-rem) was not presented prior to extinction learning. All stimuli were presented during extinction learning and during two re-extinction sessions (24 h and 6-months after extinction learning) without reinforcement. Blood oxygen level-dependent (BOLD) responses and skin conductance responses (SCRs) to both CS+ and the CS- were explored during acquisition, extinction, and in both re-extinction sessions. Regarding SCRs, the results showed that a single presentation of a conditioned stimulus did not block the return of fear during re-extinction: Fear recovery during re-extinction (24 h and 6-months after extinction learning) was observed for both CS+ compared with the CS- with no difference between CS+rem and CS+non-rem. Regarding BOLD-responses, no significant differences between CS+rem and CS+non-rem were found in region of interest (ROI)-analyses (amygdala, ventromedial prefrontal cortex) during extinction learning and both re-extinction sessions. Whole-brain analyses showed increased BOLD-responses to the CS+non-rem as compared to the CS+rem in several regions (e.g., middle frontal gyrus) during extinction learning and re-extinction (24 h after extinction learning). The present findings suggest that the effect of preventing the return of fear by disrupting reconsolidation seems to be a more labile phenomenon than previously assumed. Possible boundary conditions and implications are discussed.

The association between the 5-HTTLPR and neural correlates of fear conditioning and connectivity.

Strong evidence links the 5-HTTLPR genotype to the modulation of amygdala reactivity during fear conditioning, which is considered to convey the increased vulnerability for anxiety disorders in s-allele carriers. In addition to amygdala reactivity, the 5-HTTLPR has been shown to be related to alterations in structural and effective connectivity. The aim of this study was to investigate the effects of 5-HTTLPR genotype on amygdala reactivity and effective connectivity during fear conditioning, as well as structural connectivity [as measured by diffusion tensor imaging (DTI)]. To integrate different classification strategies, we used the bi-allelic (s-allele vs l/l-allele group) as well as the tri-allelic (low-functioning vs high-functioning) classification approach. S-allele carriers showed exaggerated amygdala reactivity and elevated amygdala-insula coupling during fear conditioning (CS + > CS-) compared with the l/l-allele group. In addition, DTI analysis showed increased fractional anisotropy values in s-allele carriers within the uncinate fasciculus. Using the tri-allelic classification approach, increased amygdala reactivity and amygdala insula coupling were observed in the low-functioning compared with the high-functioning group. No significant differences between the two groups were found in structural connectivity. The present results add to the current debate on the influence of the 5-HTTLPR on brain functioning. These differences between s-allele and l/l-allele carriers may contribute to altered vulnerability for psychiatric disorders.

Variations in central serotonergic activity - relevance of the 5-HTTLPR, life events and their interaction.

The 5-HTTLPR and its interaction with adverse life events has been studied widely; especially with regard to depression. Few studies are available relating the respective association with acute serotonergic functionality. We examined the effects of the 5-HTTLPR, life events and their interaction on serotonergic responsivity using S-citalopram (10mg) in a placebo-controlled double-blind neuroendocrine challenge paradigm (n=59 healthy males). We considered positive and negative life events, life events experienced during the last year and accumulated over the whole life span and possible mediating effects of neuroticism, extraversion and openness to experience. We demonstrated associations of life events experienced during the last year: negative life events were positively associated with cortisol-responses in the challenge paradigm (ß=0.28, p<0.05), while positive life events were inversely associated (ß=-0.29, p<0.05). Neither the main effect of 5-HTTLPR-genotype nor its interactions with life events predicted the acute serotonergic functionality. In addition, openness for feelings significantly predicted the serotonergic responsivity, while no other personality traits measured in this study mediated the effect of life events. Our results question not only the stability of serotonergic activity but, importantly, add to the literature concerning the serotonergic system as a general threshold modulating system, i.e. being associated with the processing of positive as well as negative stimuli.

Differential associations of dopamine-related polymorphisms with discrete components of reaction time variability: relevance for attention deficit/hyperactivity disorder.

BACKGROUND: Reaction time variability (RTV) is considered a valid endophenotype of attention deficit/hyperactivity disorder (ADHD). It is also often used to examine the efficacy of drug treatment or individual patients' treatment responses and has been furthermore suggested to significantly reduce the potential number of false-positive diagnoses. Among the most commonly investigated candidate genes for ADHD are DRD2, SLC6A3 (DAT), COMT and MAOA. Genetic associations have, however, proven inconclusive or inconsistent. METHODS: Due to the complexity of dopaminergic neurotransmission in the two distinct prosencephalic dopamine pathways, we examined whether the effects of dopamine-related candidate polymorphisms in the genes DRD2, SLC6A3, COMT and MAOA may be differentially associated with discrete subcomponents of RTV, rather than global RTV. A total of 260 healthy volunteers were genotyped for the aforementioned polymorphisms and performed a reaction time paradigm able to distinguish between sensory and motor reaction time. RESULTS: We found that functional polymorphisms in the genes encoding for dopamine-catabolizing enzymes (i.e. COMT and MAOA) are associated with motor RTV but not with sensory RTV, whereas vice versa the gene DRD2 influences sensory but not motor RTV. No significant associations for the gene SLC6A3 (DAT) were found. CONCLUSIONS: Our results give new insight into the inconsistent state of the literature regarding genetic associations of RTV and clearly show that the examination of subcomponents thereof explains far more variance compared to global RTV. This could be of great relevance to the use of RTV in basic research, clinical diagnostics and pharmacological studies examining the efficacy of novel drug treatments.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR.

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

Effects of pre-experience of social exclusion on hypothalamus-pituitary-adrenal axis and catecholaminergic responsiveness to public speaking stress.

BACKGROUND: Being socially excluded is associated with a variety of psychological changes and with an increased risk of disease. Today, the immediate physiological consequences of being socially excluded are not well understood. In two recent studies employing a standardized exclusion paradigm (Cyberball) we found social exclusion in this virtual game did not alter cortisol secretion directly. However, exclusion pre-experience suppresses the normal cortisol response to public speaking stress in women. The present study aims to replicate our previous finding and further elucidate it by analyzing for the first time whether this alteration of cortisol-responsiveness is associated to ACTH and whether the catecholaminergic system is affected as well. METHODS: Women were randomly assigned to Cyberball-induced exclusion (SE, n = 22) or inclusion (SI, n = 21), respectively. Immediately afterwards they were subjected to public speaking stress. Salivary cortisol, plasma ACTH, catecholamines and estradiol were assessed as were psychological distress and mood. RESULTS: Cyberball exclusion led to a highly significant immediate increase in negative affect in excluded women. After public speaking negative affect in included women increased as well and groups no longer differed. We replicate our previous finding of cortisol non-responsiveness to public speaking stress after exclusion pre-experience and find this effect to be significantly correlated with ACTH alterations. No such effects are observed for catecholamines. CONCLUSIONS: We replicated our previous study result of a suppressed cortisol stress response after a short exclusion experience via Cyberball, thereby underlining the profound effects of social exclusion on a subsequent cortisol stress response. This further demonstrates that these alterations are associated with ACTH. Lack of effects on catecholamines is discussed in view of the tend-and-befriend hypothesis but also from a methodological perspective.

MAOA-uVNTR genotype predicts interindividual differences in experimental aggressiveness as a function of the degree of provocation.

The MAOA-uVNTR has been suggested to play a role regarding aggression, however, results are inconsistent. We aimed at further elucidating potential effects of the MAOA-uVNTR on aggressiveness with respect to potential modulators: sex, experimental vs. trait aggressiveness and type of aggressiveness (proactive vs. reactive aggressiveness). We tested 239 healthy young adults (88 men/151 women). Participants were genotyped for the MAOA-uVNTR and performed a modified version of a competitive reaction time task - a commonly used and well established tool to elicit and measure aggressiveness. Furthermore, they completed a self-report scale measuring trait aggressiveness. We found a main effect of MAOA-uVNTR on a measure of reactive aggressiveness for both men and women, whereby the low-activity alleles of the MAOA-uVNTR were associated with substantially increased aggressive reactions (p<.05). This effect was unique for reactive aggressiveness. Measures of proactive aggressiveness or self reports were not associated with the MAOA-uVNTR-genotype. Our data are in line with earlier studies and indicate the MAOA-uVNTR-genotype to be specifically associated with measures of reactive impulsive experimental aggressiveness in healthy men and women. Furthermore the association between the MAOA-uVNTR genotype and aggressive responses increases in a fashion linear to the degree of provocation. This indicates that the low-functional alleles of the MAOA-uVNTR are not associated with increased aggressive behavior per se, but rather with an increased aggressive reactivity to provocation.

Dopaminergic foundations of schizotypy as measured by the German version of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE)-a suitable endophenotype of schizophrenia.

The concept of schizotypy or "psychosis proneness" captures individual differences in perceptual, cognitive, and affective experiences that may relate to a range of psychotic disorders. The concept is an important way to assess the contribution of pre-existing psychological and genetically based biological features to the development of illnesses such as schizophrenia (so called endophenotypes). The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) is a widely used multi-dimensional measure of the construct and consists of four scales which mirror several groups of psychotic symptoms: Unusual Experiences (UnEx; positive symptoms), Cognitive Disorganization (CogDis; cognitive symptoms), Introvertive Anhedonia (IntAn; negative symptoms), and Impulsive Nonconformity (ImpNon; impulsive and antisocial symptoms). For the purpose of evaluating the suitability of schizotypy as an endophenotype of schizophrenia the current version of the O-LIFE was translated into German: its psychometric properties (including re-test reliability and construct validity) were examined in a large sample (n > 1200) and compared to those of the English original. The German version was both highly reliable and consistent with the original. The study aimed to show that schizotypy as measured by the O-LIFE can indeed be regarded as an endophenotype of schizophrenia in terms of genetic associations regarding relevant dopamine-related candidate polymorphisms of schizotypy [i.e., Val(158)Met-polymorphism of the COMT gene, uVNTR of the MAOA gene, Taq1A-polymorphism of the DRD2 gene, VNTR of the SLC6A3 (DAT) gene]. We also wanted to compare the genetic associations of the O-LIFE to those published using other operationalizations of schizotypy. Our results show a large number of significant associations and borderline-significant trends between the O-LIFE sub-scales and a range of genes, thereby supporting using the O-LIFE in the search for endophenotypic markers.

Genetic variants within the dopaminergic system interact to modulate endocrine stress reactivity and recovery.

Catecholamines modulate endocrine stress reactivity by affecting regulatory influences of extra-hypothalamic brain structures on hypothalamus-pituitary-adrenal (HPA)-axis. Therefore, we aimed to investigate combined effects of functional allelic variations that affect dopamine availability in both cortical (COMT Val¹58Met polymorphism) and subcortical (DAT1 VNTR) brain regions on HPA-axis reactivity to psychosocial stress. By using a standardized laboratory stress task (public speaking) we obtained saliva cortisol samples during stress exposure and an extended recovery period in 100 healthy male adults. We report for the first time significant epistasis between COMT Val¹58Met and DAT1 VNTR on cortisol response patterns. Subjects homozygous for both the Met¹58 and the 10-repeat allele of DAT1 VNTR were characterized by markedly elevated cortisol reactivity and impaired stress recovery compared to all other groups. Our results indicate a crucial role of functional genetic variants within the dopaminergic system in the modulation of HPA-axis response patterns and highlight the need to investigate combined effects of specific candidate genes on stress-related endophenotypes.

The BDNF Val66Met polymorphism affects HPA-axis reactivity to acute stress.

BACKGROUND: Growing evidence suggests that individual differences in HPA-axis reactivity to psychosocial stress are partly due to heritable influences. However, knowledge about the role of specific genetic variants remains very limited to date. Since brain-derived neurotrophic factor (BDNF) not only exhibits neurotrophic actions but is also involved in the regulation of hypothalamic neuropeptides, we investigated the role of a common functional polymorphism within the BDNF gene (BDNF Val66Met) in the context of endocrine and cardiovascular stress reactivity. METHODS: Healthy male adults (N=100) were genotyped and exposed to a standardized laboratory stress task (Public Speaking). Saliva cortisol and self-reported mood levels were obtained at 6 time points prior to the stressor and during an extended recovery period. Furthermore, heart rate reactivity as an indicator of sympathetic activation was monitored continuously during the experimental procedure. RESULTS: We report a small, but significant effect of the BDNF Val66Met polymorphism on stress reactivity. More precisely, carriers of the met-allele showed a significantly attenuated HPA-axis and cardiovascular reactivity to the psychosocial stressor compared to subjects with the val/val genotype. Furthermore, the diminished physiological response in met-allele carriers was also attended by significantly lower self-reported ratings of perceived stress and nervousness. CONCLUSION: Our findings of a diminished endocrine and cardiovascular stress response in healthy male adults is consistent with a previously published study and adds further evidence for a crucial role of the BDNF Val66Met polymorphism in the modulation of stress reactivity.

Aggression--interactions of serotonin and testosterone in healthy men and women.

Serotonin (5-HT) and testosterone (T) have both been implicated in the regulation of aggression. Findings in humans however are very inconclusive, with respect to main effects of either system. Animal models implicate T to modulate 5-HT system activity, and furthermore have shown behaviorally relevant interactions of T and 5-HT with respect to aggression. We tested for associations between habitual T-level and 5-HT system activity, as well as behaviorally relevant interactions of T and 5-HT with respect to trait aggression in 48 healthy male and female subjects. 5-HT activity was measured by means of neuroendocrine challenge paradigm with S-citalopram. T-levels were measured in saliva samples. Trait aggression was assessed by self-report measures. T-levels were not associated with indices of central 5-HT activity. Results showed significant interaction effects between 5-HT and T for trait aggression in men only (p<0.05). Trait aggression was significantly higher in the combinations "high T+high cortisol responses" (indicating decreased 5-HT availability), and "low T+low cortisol responses" (indicating increased 5-HT availability), after S-citalopram. Results support the notion of behaviorally relevant interactions between T and 5-HT, with respect to aggression in humans, but also indicate the need for further studies.

Gene-environment interactions predict cortisol responses after acute stress: implications for the etiology of depression.

BACKGROUND: Growing evidence suggests that the serotonin transporter polymorphism (5-HTTLPR) interacts with adverse environmental influences to produce an increased risk for the development of depression while the underlying mechanisms of this association remain largely unexplored. As one potential intermediate phenotype, we investigated alterations of hypothalamic-pituitary-adrenal (HPA) axis responses to stress in individuals with no history of psychopathology depending on both 5-HTTLPR and stressful life events. METHODS: Healthy male adults (N=100) were genotyped and completed a questionnaire on severe stressful life events (Life Events Checklist). To test for gene-by-environment interactions on endocrine stress reactivity, subjects were exposed to a standardized laboratory stress task (Public Speaking). Saliva cortisol levels were obtained at 6 time points prior to the stressor and during an extended recovery period. RESULTS: Subjects homozygous for the s-allele with a significant history of stressful life events exhibited markedly elevated cortisol secretions in response to the stressor compared to all other groups, indicating a significant gene-by-environment interaction on endocrine stress reactivity. No main effect of either 5-HTTLPR (biallelic and triallelic) or stressful life events on cortisol secretion patterns appeared. CONCLUSION: This is the first study reporting that 5-HTTLPR and stressful life events interact to predict endocrine stress reactivity in a non-clinical sample. Our results underpin the potential moderating role of HPA-axis hyper-reactivity as a premorbid risk factor to increase the vulnerability for depression in subjects with low serotonin transporter efficiency and a history of severe life events.

The 5-HT1A C(-1019)G polymorphism, personality and electrodermal reactivity in a reward/punishment paradigm.

During past years the 5-HT(1A) C(-1019)G polymorphism has been associated with vulnerability to depression, anxiety-disorder and personality traits related to negative emotionality (e.g. neuroticism). Many of these studies focused on case-control comparisons or associations between genetic markers and personality traits assessed by the use of questionnaires. In contrast, overt behaviour and physiological measures in experimental paradigms, although very promising, have seldom been the focus of studies investigating the role of the 5-HT(1A) polymorphism for behaviour and psychopathology. To fill this gap, we examined the relationship between the 5-HT(1A) C(-1019)G polymorphism and reaction times (in a reward/punishment paradigm) as well as electrodermal activity, as a marker of autonomic arousal, in 123 healthy subjects. This paradigm seems very promising, as sensitivity to punishment in particular, is strongly associated to traits related to negative emotionality. Carriers of the GG genotype, which is related to increased expression of 5-HT(1A) autoreceptors, exhibited increased reaction times when they were able to win money (reward condition). In direct contrast to the reward condition, these subjects show faster reaction times in the punishment condition (losing money). Moreover, GG carriers are characterized by an enhanced electrodermal activity in all experimental conditions (win, lose and verbal feedback). Finally, the reaction-time pattern mentioned was related to higher scores on negative emotionality as revealed by self-reports. These findings demonstrate for the first time that the 5-HT(1A) polymorphism is related to personality on the level of a triadic approach including behaviour, physiology and self-reports.

TPH2 gene variation and conflict processing in a cognitive and an emotional Stroop task.

Evidence suggests that a promoter polymorphism of the tryptophan-hydroxylase 2 gene (TPH2 -703 G/T) is associated with executive control functions. The current study aimed to clarify whether this relation is restricted to a purely cognitive domain or whether such an effect can also be observed in the processing of emotional material. In a sample of 89 student subjects, a 'cognitive' and an 'emotional' Stroop paradigm were applied to measure processing of cognitive and affective conflicts. Our results suggest an impact of the TPH2 -703 G/T polymorphism on executive control in both, the cognitive as well as the emotional task. In detail, homozygous carriers of the T allele showed decelerated responses in low-conflict conditions, pointing to a rather abnormal functioning of higher-order control mechanisms. Thus, the present investigation is consistent with previous behavioural studies and adds further evidence for the impact of serotonin at the interface of cognition and emotion.

Association between a polymorphism in the promoter region of the TPH2 gene and the personality trait of harm avoidance.

In a genetic association study the role of the -703 G/T (rs4570625) polymorphism, located in the promoter region of the tryptophan hydroxylase 2 gene (TPH2), in personality traits was investigated in a sample of 404 healthy Caucasian subjects. A significant association between harm avoidance (HA), a trait related to anxiety, and the -703 G/T polymorphism was detected supporting the findings by Gutknecht and colleagues.

S-Citalopram in neuroendocrine challenge-tests: serotonergic responsivity in healthy male and female human participants.

The aim of the present study was to assess the usefulness of the selective serotonin-reuptake-inhibitor S-Citalopram as a serotonergic challenge probe in 24 healthy male and 24 healthy female participants. The participants received a single oral dose of 10 and 20mg of S-Citalopram in a placebo-controlled double blind crossover design. In female subjects phases of the menstrual cycle were controlled. Changes in concentrations of cortisol in saliva were used to indicate serotonergic reactivity. S-Citalopram induced a reliable dose dependent rise in cortisol concentrations. Results reveal a clear dose-response relationship in both sexes. However, in contrast to the 10mg condition the dosage of 20mg led to significantly higher cortisol levels in females, whereas no differences could be observed with respect to different phases of the menstrual cycle (follicular vs. luteal). Adverse side effects were reported only after 20mg. The results clearly indicate that the dosage of 10mg should be preferred when challenging males and females. Results will be discussed with regard to the further use of S-Citalopram in neuroendocrine challenge tests.