Effects of the serotonin transporter polymorphism and history of major depression on overgeneral autobiographical memory

The avBNSTGABA-VTA and avBNSTGABA-DRN pathways are respectively involved in the regulation of anxiety-like behaviors in parkinsonian rats

The anteroventral bed nucleus of stria terminalis (avBNST) is a key brain region which involves negative emotional states, such as anxiety. The most neurons in the avBNST are GABAergic, and it sends GABAergic projections to the ventral tegmental area (VTA) and the dorsal raphe nucleus (DRN), respectively. The VTA and DRN contain dopaminergic and serotonergic cell groups in the midbrain which regulate anxiety-like behaviors. However, it is unclear the role of GABAergic projections from the avBNST to the VTA and the DRN in the regulation of anxiety-like behaviors, particularly in Parkinson's disease (PD)-related anxiety. In the present study, unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta in rats induced anxiety-like behaviors, and decreased level of dopamine (DA) in the basolateral amygdala (BLA). Chemogenetic activation of avBNSTGABA-VTA or avBNSTGABA-DRN pathway induced anxiety-like behaviors and decreased DA or 5-HT release in the BLA in sham and 6-OHDA rats, while inhibition of avBNSTGABA-VTA or avBNSTGABA-DRN pathway produced anxiolytic-like effects and increased level of DA or 5-HT in the BLA. These findings suggest that avBNST inhibitory projections directly regulate dopaminergic neurons in the VTA and serotonergic neurons in the DRN, and the avBNSTGABA-VTA and avBNSTGABA-DRN pathways respectively exert impacts on PD-related anxiety-like behaviors.

Effects of serotonin transporter and receptor polymorphisms on depression

INTRODUCTION

Serotonin is highly implicated in the regulation of emotional state and the execution of cognitive tasks, so much so that the serotonin transporter genes (5-HTT, SLC6A4) and the serotonin receptor genes (HTR1A, HTR1B, HTR2A) have become the perfect candidates when studying the effects that these genes and their polymorphic variations have on depression characteristics.

OBJECTIVE

A review of research reports that have studied the effects of variations in the serotonin transporter and receptor genes on different clinical features of depression.

METHODS

A search of the Scopus, Web of Science and PubMed databases was conducted using the keywords ("depression" AND "polymorphism").

CONCLUSIONS

According to the review of 54 articles, the short allele of the 5-HTTLPR polymorphism was found to be the most reported risk factor related to the development of depression and its severity. Variations in the genes studied (SLC6A4, HTR1A, HTR2A) can generate morphological alterations of brain structures.

Emotional valence of self-defining memories in older adults: A longitudinal study

The present study aimed to evaluate the pleasantness bias and fading affect bias in self-defining memories (SDMs) and to examine the relationship between their emotional valence of SDMs and cognitive function and serotonin transporter polymorphisms (5-HTTLPR) with a prospective longitudinal method. Ninety-two older adults recalled SDMs twice at an interval of one year (T1 and T2). The results showed a pleasantness bias and a fading affect bias in SDMs. The higher the working memory was, the higher the vividness of SDMs and the higher the concordance rate of SDMs between T1 and T2. Meanwhile, cognitive performance had no effect on the emotional valence of SDMs. Additionally, the repeatedly recalled SDMs in the S/S allele carriers of the 5-HTTLPR polymorphism changed with a lower negative valence at T2 than at T1. The 5-HTTLPR polymorphism may be a plasticity factor that predicts positive outcomes in positive situations.

Effects of Serotonin Transporter and Receptor Polymorphisms on Depression

INTRODUCTION

Serotonin is highly implicated in the regulation of emotional state and the execution of cognitive tasks, so much so that the serotonin transporter genes (5-HTT, SLC6A4) and the serotonin receptor genes (HTR1A, HTR1B, HTR2A) have become the perfect candidates when studying the effects that these genes and their polymorphic variations have on depression characteristics.

OBJECTIVE

A review of research reports that have studied the effects of variations in the serotonin transporter and receptor genes on different clinical features of depression.

METHODS

A search of the Scopus, Web of Science and PubMed databases was conducted using the keywords ("depression" AND "polymorphism").

CONCLUSIONS

According to the review of 54 articles, the short allele of the 5-HTTLPR polymorphism was found to be the most reported risk factor related to the development of depression and its severity. Variations in the genes studied (SLC6A4, HTR1A, HTR2A) can generate morphological alterations of brain structures.

Hospital-based case control study and animal study on the relationship between nonylphenol exposure and depression

Objectives

The aim of this work is to explore the association between chronic exposure to nonylphenol (NP), a representative environmental endocrine disruptor (EED), and the risk of depression and its potential mechanism.

Methods

A hospital-based case control study was conducted from August to December 2018. Forty-one patients with confirmed depression and 47 healthy volunteers were recruited. In vitro, 20 rats were randomly divided into the control group (corn oil) and NP exposure group (n=10 per group), which were gavaged at a dose of 4 mg/kg w/day for 180 days.

Results

The depressed patient group had higher Zung Self-Rating Depression Scale (SDS) (P<0.001) and Self-Rating Anxiety Scale (SAS) (P<0.001) scores than the healthy group. The serum NP level (P=0.009) in the depressed group was higher than that in the healthy group, and the BDNF level (P=0.001) was lower. The serum levels of monoamine neurotransmitters dopamine (DA) (P=0.070), epinephrine (E) (P=0.001), and noradrenaline (NE) (P=0.000) were lower than those in the healthy group. In the sucrose preference test, the sucrose preference time for the exposure group of rats was lower than that of the control group (P<0.001). In the forced swim test, a longer resting time was measured for the exposure group of rats as compared to the control group (P<0.05). The level of NP (P<0.001) in the brain tissue of the NP exposure group was higher than that in the control group, and the serum level of brain-derived neurotrophic factor (BDNF) (P=0.004) was lower. Histopathological examination of the brain biopsies illustrated that the neuronal cells and nuclei in the hippocampus of the exposed group exhibited slight shrinkage.

Conclusion

Chronic exposure to NP at environmental doses will result in the accumulation of NP in the brain and blood, and induction of depression, which might be associated with the alterations in the expression levels of BDNF and monoamine neurotransmitters.

Retrieval process of overgeneral memory and the capture and executive control hypothesis: using Autobiographical Memory Test with thought sampling

The retrieval process for underlying overgeneral autobiographical memory remains unclear. In this study, we identified what leads to self-referential and categoric thoughts and examined the influence error-monitoring ability has on the reporting of categoric memories. We also examined whether cue self-relevance and/or executive control task performance are related to the number of specific memories reported. Using thought sampling, 94 college students completed the Autobiographical Memory Test, as well as a verbal fluency task and a depression scale. The results indicated that depressive symptoms and negative highly self-relevant cues were associated with self-referential/categoric thoughts during memory retrieval. Further, preceding self-referential/categoric thoughts and low error-monitoring ability predicted immediate after-reporting of categoric memories. Simultaneously, highly self-relevant cues and executive control task performance predicted the reporting of many specific memories. Subdividing the retrieval process and examining the process involved in depression are essential.

Emotional Roles of Mono-Aminergic Neurotransmitters in Major Depressive Disorder and Anxiety Disorders

A growing body of researches support a role for dysfunction of serotoninergic, noradrenergic, and dopaminergic systems in the neurobiological processes involved in major depression disorder (MDD) and anxiety disorders (ADs). The physiological changes underlying abnormal signaling of 5-HT, NE, and DA may be due to either reduced presynaptic release of these neurotransmitters or aberrant signal transductions, and thus contributing to the alterations in regulation or function of receptors and/or impaired intracellular signal processing. Animal models demonstrate crucial responsiveness to disturbance of 5-HT, NE, and DA neurotransmissions. Postmortem and biochemical studies have shown altered concentrations of 5-HT, NE, and DA metabolites in brain regions that contribute importantly to regulation of mood and motivation in patients with MDD or ADs. Neuroimaging studies have found abnormal 5-HT, NE, and DA receptors binding and regulation in regard to receptor numbers. Medications that act on 5-HT, NE, and DA neurons or receptors, such as SSRIs and SNRIs, show efficacy in both MDD and ADs. The overlapping treatment response presumably suggests a common mechanism underlying the interaction of these disorders. In this paper, we reviewed studies from multiple disciplines to interpret the role of altered 5-HT, NE and DA mono-amine neurotransmitter functions in both MDD and ADs.

5-HTTLPR polymorphism is associated with nostalgia proneness: The role of neuroticism

Nostalgia, a sentimental longing for the past, is a self-relevant and social emotion. Nostalgia proneness is associated with alleviation of distress or instability (e.g., neuroticism). Although nostalgia proneness is heritable, the specific molecular contributors to this heritability are unknown. We focused on a polymorphism in the promoter of the serotonin transporter gene (5-HTTLPR) as a possible biological basis of nostalgia proneness, because the serotonin system has been associated with sensitivity to negative experience. Participants (N = 397 adults) who had reported levels of nostalgia proneness were genotyped. A subsample also completed a measure of neuroticism. Participants with the 5-HTTLPR short allele were higher on nostalgia proneness than those without this allele. Neuroticism mediated the relation between 5-HTTLPR and nostalgia proneness. These findings enrich our understanding of the genetic and personality underpinnings of nostalgia.

Autobiographical memory dysfunctions in depressive disorders

Autobiographical memory (AM) is a ubiquitous human experience that belongs to long-term declarative memory. It plays interpersonal and intrapsychic functions. The main aim of this study is to present results of contemporary research on AM in recurrent depressive disorders. The available research literature suggests that AM dysfunctions are a precursor and risk factor for recurrent depressive disorders and that they also appear to be a consequence of depressive symptoms in a bidirectional and interacting manner. These data suggest that AM might be a viable therapeutic target for cognitive remediation strategies, given the impact of cognition on diverse clinical outcomes.

Testing the CaR-FA-X model: investigating the mechanisms underlying reduced autobiographical memory specificity in individuals with and without a history of depression

Reduced autobiographical memory specificity (AMS) is an important cognitive phenomenon in major depressive disorder (MDD), but knowledge about mechanisms is lacking. The CaR-FA-X model of Williams and colleagues (2007) proposed that 3 processes contributed to reduce AMS: capture and rumination (CaR), functional avoidance (FA), and impaired executive control (X). However, the entire CaR-FA-X model has not been tested. We addressed this gap in the literature by investigating contributions of the CaR-FA-X mechanisms to reduced AMS, alone or in interaction, in a subset of young adults (N = 439) from the Northwestern-UCLA Youth Emotion Project. Participants were classified as those with (n = 164) and without (n = 275) a history of MDD at AMS assessment. They completed measures of: AMS; rumination (the brooding factor; CaR); childhood, adolescent, and early adulthood adversity (FA); avoidant coping (FA); and verbal fluency (X). Using structural equation modeling, we found greatest support for associations between reduced AMS and the capture and rumination, and impaired executive control mechanisms. In those with and without a history of MDD, brooding and verbal fluency interacted to contribute to reduced AMS. For participants without a history of MDD, lower verbal fluency (indicating impaired executive control) was associated with reduced AMS among those high on brooding. For participants with a history of MDD, lower verbal fluency was associated with reduced AMS among those low on brooding. The first finding was consistent with the CaR-FA-X model but the latter was not. Implications for conceptualizations of reduced AMS and its mechanisms are discussed.