Amygdala norepinephrine levels after training predict inhibitory avoidance retention performance in rats.

Previous findings indicate that footshock and several drugs that modulate memory consolidation alter norepinephrine (noradrenaline) release in the amygdala, as assessed by in vivo microdialysis and high-performance liquid chromatography. Such findings suggest that norepinephrine release in the amygdala may be critical for regulating memory consolidation. The present study was the first to examine the relationship between norepinephrine release in the amygdala assessed after inhibitory avoidance training and 24-h retention performance within individual animals. Norepinephrine levels increased to > 300% of pretraining baseline 30 min after training and remained elevated for 2 h. In individual rats, the increase in norepinephrine levels after training correlated highly with 24-h retention performance. These findings indicate that the degree of activation of the noradrenergic system within the amygdala in response to a novel, emotionally arousing experience predicts the extent of long-term memory for that experience.