EXPOSURE TO INESCAPABLE BUT NOT ESCAPABLE SHOCK INCREASES EXTRACELLULAR LEVELS OF 5-HT IN THE DORSAL RAPHE NUCLEUS OF THE RAT

The effects of escapable and yoked inescapable electric tailshocks on extracellular levels of serotonin (5-HT) in the dorsal raphe nucleus w ere measured by in vivo microdialysis. In comparison to either control rats or to their own preshock baseline, rats exposed to inescapable s hock showed an increase in extracellular 5-HT within 25 min of shock i nitiation, and 5-HT levels continued to rise during the remainder of t he shock session. Rats that were exposed to comparable shock treatment , but that were given the opportunity to escape, did not show an incre ase in 5-HT. Rats that were restrained but not shocked also did not sh ow an increase in 5-HT. These results add further support to suggestio ns that serotonegic changes occur in the dorsal raphe nucleus during i nescapable shock and that such changes may contribute to the behaviora l effects of inescapable shock. (C) 1998 Elsevier Science B.V.