TEMPORAL FACTORS IN THE EFFECT OF RESTRAINT STRESS ON MORPHINE-INDUCED BEHAVIORAL SENSITIZATION IN THE RAT (VOL 117, PG 102, 1995)

The role of associative factors in the effect of 15 min/day of restrai nt stress on morphine-induced behavioral sensitization was examined. M ale rats were initially given seven systemic (10 mg/kg, IF) or intrave ntral tegmental area (VTA, 5 mu g/side) injections of morphine, and we re exposed to restraint, either just prior to drug injection (Paired-S tress) or 24 h after injection (Unpaired-Stress), or to no restraint ( Control). In subsequent tests for behavioral sensitization to low dose s of morphine (0.75 or 3.0 mg/kg, IF), animals in the Paired-Stress co ndition were more active than animals in the Unpaired-Stress or Contro l conditions. These results indicate that temporal and possibly associ ative factors may contribute to stress-induced changes in sensitizatio n to the behavioral activating effects of opioids.