Priming stimulation of locus coeruleus facilitates memory retrieval in the rat.

Rats were trained to run a linear maze for food reinforcement. During the 5-week retention interval, they were implanted under electrophysiological control with fine stimulating electrodes aimed at the nucleus locus coeruleus (LC). When tested 5 weeks after training, control rats showed forgetting in that they made significantly more errors at the test trial than at the last training trial. Low-level stimulation of LC immediately before the test alleviated the forgetting in that this group made significantly fewer errors than the non-stimulated group on two successive days. The results are taken as behavioral evidence of a role for noradrenergic projections from LC in memory and attention.