Animal studies have shown that fear memories can change when recalled, a process referred to as reconsolidation. We found that oral administration of the -adrenergic receptor antagonist propranolol before memory reactivation in humans erased the behavioral expression of the fear memory 24 h later and prevented the return of fear. Disrupting the reconsolidation of fear memory opens up new avenues for providing a long-term cure for patients with emotional disorders.Some details:
The conditioned fear response was measured as potentiation of the eyeblink startle reflex to a loud noise (40 ms, 104 dB) by electromyography of the right orbicularis oculi muscle. Stronger startle responses to the loud noise during the fear-conditioned stimulus (CS1+) as compared with the control stimulus (CS2-) reflects the fearful state of the participant elicited by CS1+. Startle potentiation taps directly into the amygdala, and fear-conditioning procedures yield highly reliable and robust startle potentiation.
Figure. (click to enlarge) (a–f) Mean startle potentiation to the fear-conditioned stimulus (CS1), the control stimulus (CS2) and noise alone (NA) trials (left) and mean expectancy scores of the unconditioned stimulus to CS1 and CS2 trials (right) during acquisition (trial 1–8), extinction (trial 1–10) and test (trial 1–5) for the placebo (n = 20, a,b), propranolol reactivation (n = 20, c,d) and propranolol without reactivation (n = 20, e,f) group. CS1+ refers to the fear conditioned stimulus during acquisition, CS1- refers to the fear conditioned stimulus during extinction and test, CS1-R refers to the reactivation of the fear conditioned stimulus and CS2- refers to the control stimulus during all phases of the experiment. Error bars represent s.e.m.