NOREPINEPHRINE RELEASE IN THE AMYGDALA IN RESPONSE TO FOOTSHOCK STIMULATION

Extensive evidence suggests that many drugs and hormones influence mem ory storage by modulating training-induced release of norepinephrine ( NE) within the amygdala. This experiment used in vivo microdialysis an d high-performance liquid chromatography to examine norepinephrine NE release in the amygdala induced by footshock stimulation typically use d in inhibitory avoidance training. Sprague-Dawley rats were implanted bilaterally with cannulae aimed at the amygdala. One to two weeks lat er, microdialysis probes were inserted (unilaterally) and the animals were placed in a box with a stainless-steel grid floor through which a single footshock (0.55 mA, 1.0 s) was administered either 45.5 (N = 5 ) or 180.5 (N = 4) min later. Samples were collected and analyzed at 1 5-min intervals. In both groups, the footshock stimulation increased N E levels to approximately 75% above basal levels in the first sample c ollected after the footshock and the levels returned to baseline withi n 30 min. The findings are consistent with pharmacological evidence su ggesting that NE released by arousing stimulation is involved in regul ating memory storage. (C) 1996 Academic Press, Inc.