Memory retrieval enhancement by locus coeruleus stimulation: evidence for mediation by beta-receptors.

Rats were trained in a complex food-motivated maze task, then implanted with indwelling stimulating electrodes in the noradrenergic nucleus locus coeruleus (LC). When tested 4 weeks later, they showed significant forgetting. Electrical stimulation of the LC alleviated forgetting in that stimulated rats made no more errors during the test than they did on the last learning trial. Systemic treatment with the beta noradrenergic antagonist propranolol blocked the effect of stimulation, suggesting that the memory facilitation is mediated through a beta-receptor.