Stressor controllability modulates stress-induced serotonin but not dopamine efflux in the nucleus accumbens shell

The ability of an organism to control a stressor can modulate many of the consequences of stress. Previous research indicates that uncontrollable stress (inescapable shock, IS) activates serotonergic (5-HT) neurons of the dorsal raphe nucleus (DRN) to a greater degree than controllable stress (escapable shock, ES), potentiating 5-HT efflux in the DRN and in target regions. Previous research also indicates that IS selectively affects dopamine (DA) efflux. The present study measured 5-HT and DA efflux in the NAc shell during IS or ES using in vivo microdialysis. Male Sprague Dawley rats with probes in the NAc shell were dialysed while subjected to 100 1.0 mA tailshocks. Rats were run in yoked pairs in wheel-turn boxes such that one rat (ES) in the pair could terminate the shock received by both himself and his yoked (IS) partner by a behavioral response. No stress controls remained in the dialysis bowls. 5-HT efflux selectively increased during IS, and remained increased throughout as well as after the stress session. There was no effect of stress on DA efflux. These results indicate that the NAc 5-HT response is preferentially sensitive to stress and can be modulated by stressor controllability.