Region-specific reductions of intracranial self-stimulation after uncontrollable stress: possible effects on reward processes.

Rates of responding for intracranial self-stimulation from the medial forebrain bundle, nucleus accumbens and substantia nigra were evaluated in mice that had been exposed to either escapable shock, yoked inescapable shock or no shock treatment. Whereas performance was unaffected by escapable shock, marked reductions of responding from the medial forebrain bundle and nucleus accumbens were evident following the uncontrollable shock treatment. Responding from the substantia nigra was unaffected by the stress treatment. Uncontrollable shock is thought to reduce the rewarding value of responding for electrical brain stimulation from those brain regions in which stressors are known to influence dopamine activity.