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Propranolol Wipes out Emotional Response to Fearful Memory

NEW YORK (Reuters Health) Feb 17 - The beta-blocker propranolol can eliminate the fearful aspect of an emotional memory, according to psychologists at the University of Amsterdam, The Netherlands.

"Once emotional memory is established, it appears to last forever," Dr. Merel Kindt and associates report in February 15 early online issue of Nature Neuroscience. However, "if emotional memory could be weakened or even erased, then we might be able to eliminate the root of many psychiatric disorders, such as post-traumatic stress disorder."

They comment that reactivated fear memories following induction of a fear association in rats could be prevented long-term by infusion of propranolol into the amygdala.

To see whether propranolol would have a similar effect in humans, Dr. Kindt's group conducted a randomized trial in 40 volunteers, in whom fearful memories were created on day one by applying a mild shock when they looked at pictures of spiders. The conditioned fear response was measured as potentiation of the eyeblink startle reflex to a loud noise by electromyography of the right orbicularis oculi muscle.

The next day, subjects exhibited similar startle responses when again shown the spider pictures.

On day three, 20 subjects were given oral propranolol 40 mg and 20 were given placebo. Subsequently, during reactivation of the fear memory, propranolol was found to have eliminated the differential startle response, whereas the differential startle response remained stable in the placebo group.

"Notably," Dr. Kindt and colleagues write, "the propranolol manipulation left the declarative memory for the acquired contingency between the conditioned and unconditioned stimulus intact, but this knowledge no longer produced emotional effects."

"Disrupting the reconsolidation of fear memory opens up new avenues for providing a long-term cure for patients with emotional disorders," they conclude.

Nat Neurosci 2009.