Intraventricular administration of D-Ala2-Met5-enkephalinamide induces rapid recovery of responding for electrical brain stimulation from the ventral tegmental area following uncontrollable footshock

The effects of uncontrollable footshock were assessed in CD-1 mice responding for electrical brain stimulation (ICSS) from the dorsal aspects of the ventral tegmental area (VTA). Uncontrollable footshock provoked a marked reduction of responding for ICSS immediately, 24 h and 168 h following initial stressor exposure. Intraventricular administration of the neuropeptide, D-Ala2-Met5-enkephalinamide (DALA) (1 microgram/microliter delivered in a 1-microliter volume) following induction of reward alterations from the dorsal VTA provoked a rapid recovery of responding for ICSS in the immediate poststressor interval. This ameliorative effect of the neuropeptide deteriorated 24 h after initial exposure to uncontrollable footshock and was absent 1 week later. These data are discussed with respect to stressor-induced anhedonia in the mesocorticolimbic system.