Fear learning triggers structural changes at GABAergic synapses in the basal amygdala

Background In Pavlovian fear conditioning, in which initially a conditioned stimulus (CS) is repeatedly paired with an aversive stimulus (US), animals learn to associate CS with US, hence attaching emotional significance to sensory stimuli. Conditioned fear can be suppressed when the CS is repeatedly presented alone, a phenomenon known as fear extinction. Previous studies suggest that the mechanisms underlying fear conditioning involve inhibitory neurotransmission through GABAA receptors. GABAA receptors are generally composed of two a, two b and one g subunits. Sixteen GABAA receptor subunits have been identified in mammals, which indicates that these receptors may have multiple biophysical and pharmacological properties. Recent work showed that fear conditioning induces a dramatic downregulation of benzodiazepine binding sites and transcripts for gephyrin and some GABAA receptor subunits in the basal nucleus of the amygdala (BA), which were restored to control levels after fear extinction.