ADRA2B genotype differentially modulates stress-induced neural activity in the amygdala and hippocampus during emotional memory retrieval.

RATIONALE: Noradrenaline interacts with stress hormones in the amygdala and hippocampus to enhance emotional memory consolidation, but the noradrenergic-glucocorticoid interaction at retrieval, where stress impairs memory, is less understood.
OBJECTIVES: We used a genetic neuroimaging approach to investigate whether a genetic variation of the noradrenergic system impacts stress-induced neural activity in amygdala and hippocampus during recognition of emotional memory.
METHODS: This study is based on genotype-dependent reanalysis of data from our previous publication (Li et al. Brain Imaging Behav 2014). Twenty-two healthy male volunteers were genotyped for the ADRA2B gene encoding the α2B-adrenergic receptor. Ten deletion carriers and 12 noncarriers performed an emotional face recognition task, while their brain activity was measured with fMRI. During encoding, 50 fearful and 50 neutral faces were presented. One hour later, they underwent either an acute stress (Trier Social Stress Test) or a control procedure which was followed immediately by the retrieval session, where participants had to discriminate between 100 old and 50 new faces.
RESULTS: A genotype-dependent modulation of neural activity at retrieval was found in the bilateral amygdala and right hippocampus. Deletion carriers showed decreased neural activity in the amygdala when recognizing emotional faces in control condition and increased amygdala activity under stress. Noncarriers showed no differences in emotional modulated amygdala activation under stress or control. Instead, stress-induced increases during recognition of emotional faces were present in the right hippocampus.
CONCLUSION: The genotype-dependent effects of acute stress on neural activity in amygdala and hippocampus provide evidence for noradrenergic-glucocorticoid interaction in emotional memory retrieval.