Background: Previous studies indicate that morphine dependent and withdrawal from chronic opiates enhanced anxiety-related behaviours in novel and stressful conditions in rats. Recent studies have shown that exposure to a stressor generates a wide variety of adaptive responses, while enhancing abilities to adopt with the stressor. Therefore, the aim of this study was to examine the effect of chronic restraint stress and acute water immersion (WI) stress on the anxiety profile in morphine-dependent rats.
Methods: Thirty two rats were injected with twice daily doses (10 mg/kg, subcutaneous, at 12 hour intervals) of morphine over a period of 10 days in the presence or absence chronic restraint stress (1 hour/day). On day 11, two hour after morphine injection, anxiety-like behaviours were tested in the elevated plus-maze model in the presence or absence acute water immersion stress. Rats were divided into four groups: dependent- No restraint stress (D/NRS), dependent- restraint stress (D/RS), dependent- restraint stress+ water immersion stress (D/RS+WI), dependent- water immersion stress (D/WI).
Results: Finding have shown that D/RS+WI rats exhibited an increase in the elevated plus-maze open arm entries and time as compared with the control groups (P=0.018 and P=0.037, respectively). Also, this measure was significantly lower in the WI rats than the D/RS+WI rats (P=0.049 and P=0.031, respectively).
Conclusion: Our findings indicate that chronic restraint stress followed by acute water immersion stress decreases the severity of the anxiogenic-like behaviours in morphine dependent rats; thus it may have a therapeutic application in the treatment of the asso-ciated disorders in addiction.