Low-frequency stimulation of dorsal norephinephrine bundle reverses behavioral long-term potentiation and learning performance in rats.

Abstract Dorsal norepinephrine bundle (DNEB) is the major source of noradrenergic input to the hippocampus and norepinephrine could regulate long-term potentiation (LTP) reversal. In the present study, we investigated the effects of low-frequency stimulation (LFS) of DNEB on behavioral LTP and Y-maze learning task, by using electrophysiological recording in freely moving rats combined with behavioral tests. We found that LFS on DNEB, including 1 and 5 Hz, could inhibit reversibly basal synaptic transmission within 100-min recordings in hippocampal perforant path projections to dentate gyrus (PP-DG) pathway. 1-Hz stimulating DNEB, delivered 5 min after the daily training session, reverses behavioral LTP completely and depresses the behavioral learning as well. However, 5-Hz-treated only reverses behavioral LTP partially and reduces the behavioral learning accordingly. These results indicate that behavioral LTP in PP-DG pathway can be reversed by LFS on DNEB, and display a similar impact on Y-maze learning performance. Our data provide a new characterization of LTP reversibility and will ultimately be helpful in understanding how new information is to detect and determine storage in the hippocampus.