Increased septal 5-HIAA efflux in rats that do not develop learned helplessness after inescapable stress

Learned helplessness is a behavioral deficit that can be induced by exposur e to inescapable stress. Previous studies have implicated the lateral septu m in mediating this phenomenon, and in this brain region, serotonin plays a n important role in the development, maintenance, prevention, and reversal of learned helplessness behavior. Using the technique of in vivo microdialy sis, we measured the efflux of serotonin (5-HT), dopamine (DA), and their r espective metabolites, 5-hydroxyindoleacetic acid (5-HIAA) and 3,4-dihydrox yphenylacetic acid (DOPAC), from the lateral septum of rats that either dev eloped or did not develop learned helplessness. During the microdialysis se ssion all rats were subjected to restraint stress. Control groups included naive, home cage rats as well as tested control rats that were subjected to the identical handling, restraint, and shuttlebox testing as the rats that received inescapable shock. Overall, levels of 5-HIAA were significantly h igher in non-helpless rats. There were no significant effects of restraint or differences in levels of 5-HT, DA, or DOPAC. We propose that this increa se in 5-HIAA is indicative of an overall increase in serotonin metabolism i n the lateral septum of rats that do not become helpless after inescapable stress. This increased serotonin metabolism in the lateral septum may prote ct the animal from adverse behavioral consequences of inescapable stress, J . Neurosci. Res. 61, 101-106, 2000. Published 2000 Wiley-Liss, Inc.(dagger) .