The Effects of Noradrenergic Blockade on Extinction in Humans

The process of reconsolidation has attracted much attention because of its potential application for the treatment of psychiatric disorders. Here, we investigate a possible boundary condition of disrupting reconsolidation with the noradrenergic antagonist propranolol in humans. Reconsolidation can be initiated by retrieval of an acquired fear memory, which is in procedure equivalent to extinction training. If memory retrieval promotes the formation of a novel extinction memory trace, propranolol may interfere with extinction rather than with reconsolidation. Using a differential fear conditioning paradigm, we demonstrate that administration of propranolol (double-blind placebo controlled) prior to repetitive unreinforced CS presentations did not affect extinction at a physiological level (startle reflex and skin conductance). At a cognitive level, propranolol directly impaired extinction learning. These findings indicate that careful selection of timing parameters is essential to ensure that pharmacological agents interfere with the intended memory process to reduce fear.