ESCAPABLE AND INESCAPABLE STRESS DIFFERENTIALLY AND SELECTIVELY ALTEREXTRACELLULAR LEVELS OF 5-HT IN THE VENTRAL HIPPOCAMPUS AND DORSAL PERIAQUEDUCTAL GRAY OF THE RAT

The effects of escapable and yoked inescapable electric tailshocks on extracellular levels of serotonin (5-HT) in the ventral hippocampus an d dorsal periaqueductal gray (dPAG) were measured by in vivo microdial ysis. Inescapable, but not escapable shock increased extracellular 5-H T in the ventral hippocampus relative to restrained controls. Basal le vels of 5-HT were elevated 24 h after inescapable shock, and previousl y inescapably shocked subjects exhibited an exaggerated 5-HT response to 2 brief Footshocks. In contrast, escapable, but not inescapable sho ck, increased extracellular 5-HT in the dPAG, increased basal 5-HT in the dPAG 24 h later, and led to an enhanced 5-HT response to subsequen t brief footshock. (C) 1998 Elsevier Science B.V. All rights reserved.