Escapable and inescapable stress differentially alter extracellular levels of 5-HT in the basolateral amygdala of the rat.

The effects of escapable and yoked inescapable electric tailshocks on extracellular levels of serotonin (5-HT) in the basolateral amygdala were measured by in vivo microdialysis. Inescapable, but not escapable, shock increased extracellular 5-HT in the amygdala relative to restrained controls. Basal levels of 5-HT were elevated 24 h after inescapable shock, and previously inescapably shocked subjects exhibited an exaggerated 5-HT response to two brief footshocks. Levels of extracellular 5-HIAA did not follow any particular pattern and were not correlated with the changes in 5-HT.