Identification of a novel 12-nucleotide insertion polymorphism in the promoter region of ADRA2B: full linkage with the 9-nucleotide deletion in the coding region and influence on transcriptional activity

Dissociable contributions of the amygdala to the immediate and delayed effects of emotional arousal on memory

Emotional arousal enhances memory encoding and consolidation leading to better immediate and delayed memory. Although the central noradrenergic system and the amygdala play critical roles in both effects of emotional arousal, we have recently shown that these effects are at least partly independent of each other, suggesting distinct underlying neural mechanisms. Here we aim to dissociate the neural substrates of both effects in 70 female participants using an emotional memory paradigm to investigate how neural activity, as measured by fMRI, and a polymorphism in the α_2B-noradrenoceptor vary for these effects. To also test whether the immediate and delayed effects of emotional arousal on memory are stable traits, we invited back participants who were a part of a large-scale behavioral memory study ∼3.5 yr ago. We replicated the low correlation of the immediate and delayed emotional enhancement of memory across participants (r = 0.16) and observed, moreover, that only the delayed effect was, to some degree, stable over time (r = 0.23). Bilateral amygdala activity, as well as its coupling with the visual cortex and the fusiform gyrus, was related to the preferential encoding of emotional stimuli, which is consistent with affect-biased attention. Moreover, the adrenoceptor genotype modulated the bilateral amygdala activity associated with this effect. The left amygdala and its coupling with the hippocampus was specifically associated with the more efficient consolidation of emotional stimuli, which is consistent with amygdalar modulation of hippocampal consolidation.

A 9-nucleotide Ins/Del in ADRA2B modulates orientation of attention to facial expressions and emotional words

Norepinephrine is involved in the arousal of attention and the treatment of affective disorders. Therefore, we hypothesized that adrenergic receptors underpinned individual differences in attention regulation and emotional processes of healthy populations. Here, we investigated to what extent the expression of ADRA2B, an adrenergic receptor, modulated attention regulation and emotional processes. We evaluated orientation of attention, emotion regulation, and pleasantness ratings of expressions and words in 665 college students, and then genotyped the +901 Ins/Del variants in ADRA2B of these participants. The results indicated that +901 Ins/Del significantly modulated orientation of attention to facial expressions and emotional words, such that the Del allele facilitated reorientation to the originally attended locations. However, this polymorphism exerted no significant effects on emotional regulation of attention and pleasantness ratings of emotional stimulus. These findings suggest that ADRA2B is closely related to the individual difference in human attention orientation, but not to the individual difference in emotional processing.

Alpha 2B adrenoceptor genotype moderates effect of reboxetine on negative emotional memory bias in healthy volunteers

Evidence suggests that emotional memory plays a role in the pathophysiology of depression/anxiety disorders. Noradrenaline crucially modulates emotional memory. Genetic variants involved in noradrenergic signaling contribute to individual differences in emotional memory and vulnerability to psychopathology. A functional deletion polymorphism in the α-2B adrenoceptor gene (ADRA2B) has been linked to emotional memory and post-traumatic stress disorder. The noradrenaline reuptake inhibitor reboxetine attenuates enhanced memory for negative stimuli in healthy and depressed individuals. We examined whether the effect of reboxetine on emotional memory in healthy individuals would be moderated by ADRA2B genotype. ADRA2B deletion carriers demonstrated enhanced emotional memory for negative stimuli compared with deletion noncarriers, consistent with prior studies. Reboxetine attenuated enhanced memory for negative stimuli in deletion noncarriers but had no significant effect in deletion carriers. This is the first demonstration of genetic variation influencing antidepressant drug effects on emotional processing in healthy humans.

Haplotype polymorphism in the alpha-2B-adrenergic receptor gene influences response inhibition in a large Chinese sample

Response inhibition refers to the suppression of inappropriate or irrelevant responses. It has a central role in executive functions, and has been linked to a wide spectrum of prevalent neuropsychiatric disorders. Increasing evidence from neuropharmacological studies has suggested that gene variants in the norepinephrine neurotransmission system make specific contributions to response inhibition. This study genotyped five tag single-nucleotide polymorphisms covering the whole alpha-2B-adrenergic receptor (ADRA2B) gene and investigated their associations with response inhibition in a relatively large healthy Chinese sample (N=421). The results revealed significant genetic effects of the ADRA2B conserved haplotype polymorphisms on response inhibition as measured by stop-signal reaction time (SSRT) (F(2, 418)=5.938, p=0.003). Individuals with the AAGG/AAGG genotype (n=89; mean SSRT=170.2 ms) had significantly shorter SSRTs than did those with either the CCAC/AAGG genotype (n=216; mean SSRT=182.4 ms; uncorrected p=0.03; corrected p=0.09) or the CCAC/CCAC genotype (n=116; mean SSRT=195.8 ms; corrected p<0.002, Cohen's d=0.51). This finding provides the first evidence from association research in support of a critical role of the norepinephrine neurotransmission system in response inhibition. A better understanding of the genetic basis of response inhibition would allow us to develop more effective diagnosis, treatment, and prevention of deficient or underdeveloped response inhibition as well as its related prevalent neuropsychiatric disorders.

Lack of association between ADRA2B-4825 gene insertion/deletion polymorphism and migraine in Chinese Han population

OBJECTIVE

The present study aimed to estimate the association between susceptibility to migraine and the 12-nucleotide insertion/deletion (indel) polymorphism in promoter region of alpha(2B)-adrenergic receptor gene (ADRA2B).

METHODS

A case-control study was carried out in Chinese Han population, including 368 cases of migraine and 517 controls. Genomic DNA was extracted from blood samples, and DNA fragments containing the site of polymorphism were amplified by PCR. Data were adjusted for sex, age, migraine history and family history, and analyzed using a logistic regression model.

RESULTS

There was no association between indel polymorphism and migraine, at either the allele or the genotype level.

CONCLUSION

These findings do not support a functional significance of ADRA2B indel polymorphism at position -4825 relative to the start codon in the far upstream region of the promoter in the present migraine subjects.