UNCONTROLLABLE STRESS POTENTIATES MORPHINES REWARDING PROPERTIES

Strategies used to explore the role of stressors in drug addiction inc lude measuring stressor's effects on drug's rewarding properties. The current investigation explored the effect of an acute stressor on morp hine conditioned place preference. Twenty-four hours following either inescapable tail shock or home-cage control treatment, all subjects we re conditioned with morphine (0, 1, 2, and 3 mg/kg SC) over 2 days, an d later tested for conditioned place preference. Inescapably shocked s ubjects demonstrated a potentiated place preference compared to contro ls. The inescapable shock-induced potentiated place preference develop ed even when conditioning was delayed until 6 and 7 days following the stressor, while no longer occurring after a 14- and 15-day interval. The potentiation was not a result of reduced locomotion in the inescap ably shocked subjects, as activity in inescapably shocked and home-cag e control subjects was the same following ''mock'' saline conditioning . Furthermore, the anxiogenic 6,7-dimethoxy-4-ethyl-beta-carboline-3-c arboxylate (DMCM) (0.3 mg/kg IP), which produces effects similar to th ose produced by inescapable shock, also potentiated morphine place pre ference. In addition, the potentiation in inescapably shocked subjects was dependent upon the stressor's uncontrollability, as identical esc apable shock did not potentiate place preference above control subject s. Finally, the inescapable shock-induced potentiated place preference was drug specific, as amphetamine place preference was not affected. (C) 1998 Elsevier Science Inc.