---

Background & Objective: The effects of acute and chronic exposures to opiate drugs on anxiety process are controversial. Acute morphine injection showed the beneficial effects on anxiety. Morphine withdrawal induced severe anxiety response in morphine dependence rats. Whereas, the effects of chronic administrations of morphine on anxiety process are less studied. Furthermore, this study was designed to assess the role of morphine dependence on the level of anxiety in Rat. Materials & Methods: In this experimental study, Twenty male Wistar rats (250-300 gr) were made dependent by chronic administration of morphine in drinking water that lasted at least 21 days. Control groups received only sucrose in their water. This study utilized the elevated plus- maze model to evaluate anxiogenic-like behavior in rats. Four fundamental behavior patterns were recorded for 5 minutes: the time spent on open arms, the number of entries into open arms, stretched-attend posture and defecation. Immediately after test, the locomotor activity of each animal was tested by using an automated activity monitor system. The data were analyzed by independent t-test and two-way analysis of variance (ANOVA). Results: Finding indicated that the time spent on open arms and the numbers of entries into open arms were significantly shorter in morphine dependence group than control group (P<0.05). Also, the numbers of stretched-attend posture and defecation were significantly higher in morphine group (P<0.05). Whereas, there were no significant differences between groups in locomotor activity. Conclusion: This study showed that dependent rats may rapidly predispose anxiogenic- like effects in stressful conditions and without the effect on motor activity.

---

Background and Objective: Exposure to a stressor generates a wide variety of adaptive responses and alters the pharmacological effects of opioids. Common neural pathways are activated by morphine and stress. This study was done to determine the effect of chronic restraint stress and acute water immersion stress on the severity of naloxone precipitated morphine withdrawal manifestation in morphine-dependent rats. Methods: In this experimental study, 32 adult male Wistar rats were allocated into four groups equally including: morphine-dependent - no chronic restraint stress (D/NS) (Control), morphine-dependent with chronic restraint stress (D/R), morphine-dependent with acute water immersion stress (D/WI) and morphine-dependent with chronic restraint stress under acute water immersion stress (D/R+WI). Rats were injected with bi-daily doses (10 mg/kg/bw, sc, at 12h intervals) of morphine over a period of 10 days in the presence or absence of restraint stress (1 h/day). On day 11, immediately after naloxone hydrochloride injection (2mg/kg/bw, ip), withdrawal manifestation were recorded. Water immersion stress was performed prior to naloxone injection in D/WI and D/R+WI groups. Results: The overall score of morphine withdrawal was significantly lower in D/RS and D/RS+WI rats in compared to controls (P<0.05). Among the graded signs, the mean number of abdominal contractions and jumps was reduced in D/RS+WI and D/RS rats in compared to control groups (P<0.05). Among the checked signs, the number of rats per group with erection and genital grooming were reduced in restraint rats by 25% than control group (P<0.05). Conclusion: Chronic restraint stress with or no acute water immersion stress diminished severity of dependency on morphine. Thus, restraint stress may be applied as a method to ameliorate some of the withdrawal behavioural consequences of morphine.