Posttraining infusion of norepinephrine and corticotropin releasing factor into the bed nucleus of the stria terminalis enhanced retention in an inhibitory avoidance task.

The present study investigated whether the bed nucleus of the stria terminalis (BNST) is involved in formation and retrieval of affective memory. Male Wistar rats with cannulae bilaterally implanted into the BNST were trained on a one-trial step-through inhibitory avoidance task. Shortly after training they received bilateral intra-BNST infusion of lidocaine, various noradrenergic drugs, or corticotropin releasing factor (CRF). Results showed that posttraining intra-BNST infusion of lidocaine impaired retention. Posttraining intra-BNST infusion of norepinephrine or the alpha1 antagonist prazosin induced a dose- and time-dependent retention enhancement or deficit, respectively. The enhancing effect of norepinephrine was mimicked by the alpha1 agonist phenylephrine, and antagonized by prazosin at a non-impairing dose. Posttraining intra-BNST infusion of the alpha2 antagonist idazoxan or the beta antagonist propranolol failed to affect retention. Posttraining intra-BNST infusion of CRF also enhanced retention in a dose-dependent manner. Various drugs infused shortly before testing did not significantly influence locomotor activity and retention. These findings, taken together, suggest that the BNST is involved in memory formation processes for affective experience and norepinephrine released in the BNST acting via alpha1 receptors plays a critical role in this function.