Strain-specific effects of inescapable shock on intracranial self-stimulation from the nucleus accumbens.

Responding for electrical stimulation from the nucleus accumbens was assessed in 3 inbred strains of mice (DBA/2J, C57BL/6J and BALB/cByJ) following exposure to uncontrollable footshock. While the operant response was most readily acquired in the DBA/2J strain, exposure to inescapable shock in this strain induced a marked deterioration of self-stimulation responding, which tended to dissipate over a 168-h period. In contrast to these mice, the stressor did not affect self-stimulation responding in the C57BL/6J strain, and produced a transient enhancement of responding in BALB/cByJ mice. It appears that although uncontrollable aversive events may engender an anhedonic effect, such an outcome is strain-dependent. These data suggest the importance of considering individual and genetic differences in the development of animal models of depression.