Response of amygdalar norepinephrine to footshock and GABAergic drugs using in vivo microdialysis and HPLC

These studies used in vivo microdialysis and high-performance liquid chroma tography (HPLC) to examine levels of norepinephrine (NE) within the amygdal a in response to both footshock and GABAergic compounds. In Experiment 1, m icrodialysis probes were inserted into a previously implanted guide cannula aimed at the amygdala and the level of NE was examined in response to foot shock. A 0.55 mA (2 s) footshock induced a significant increase in NE level s when the microdialysis probe was located within the amygdala; levels of N E did not differ from baseline in rats with microdialysis probes located ou tside the amygdala. Experiment 2 examined the effects of the GABAergic anta gonist, picrotoxin, the GABAergic agonist, muscimol, and saline on NE level s in the amygdala. Rats treated systemically with picrotoxin showed a drama tic increase in levels of NE within the amygdala. In contrast, systemic inj ection of muscimol resulted in decreased levels of NE. These findings are c onsistent with the hypothesis that drugs that are capable of modulating mem ory do so by altering levels of NE within the amygdala. (C) 1999 Elsevier S cience B.V. All rights reserved.