Memory for emotional events: differential effects of centrally versus peripherally acting β-blocking agents

Substantial evidence from animal research indicates that enhanced memory associated with emotional experiences involves activation of the β-adrenergic system. This hypothesis is further supported by the finding in human subjects that blockade of β-adrenergic receptors with propranolol selectively reduced memory for emotional events. In the present study, we compared the effects of propranolol, a lipid soluble drug which crosses the blood-brain barrier easily, with those of nadolol, a water soluble drug which crosses the blood-brain barrier to a considerably lesser extent, to determine whether the effect involved peripheral or central β-adrenergic receptors. The effects of these drugs, taken before subjects watched a slide show that was either emotionally arousing or relatively neutral in content, were tested 1 week later with a surprise memory test. Consistent with previous results, propranolol impaired memory (recall and recognition) in the subjects who saw the emotional version of the slide show. In contrast, nadolol did not impair memory of the emotional slide show. These results indicate that the blockade of central β-adrenergic receptors is responsible for the reduction in storage of emotional events. The results support the view that memory of a mild emotional event involves activation of central, but not necessarily peripheral β-adrenergic receptors.