Anxiety-like behavior profile in morphine dependent rats exposed to acute and chronic stress

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

Protective effects of Desmopressin acetate on retention of spatial memory deficits induced by post-traumatic stress disorder in Rats

Background and Objective: Post-traumatic stress disorder (PTSD) impairs spatial learning and memory. Desmopressin acetate ameliorates the cognitive deficits induced by electroconvulsive shock. This study was designed to evaluate the protective effects of Desmopressin acetate on retention of spatial memory deficits induced by post-traumatic stress disorder in rats. Materials and Methods: In this experimental study twenty one male Wistar rats were used. Animals were trained for 5 consecutive days in Morris water maze and then were randomly assigned in three groups (Vehicle + Sham, Saline + PTSD and Desmopressin acetate + PTSD) and tested in a probe 60 sec in 24h after the last acquisition trial. The groups of PTSD+Desmopressin acetate rats and vehicle+sham, saline+PTSD were injected Desmopressin acetate (10 micro gr/kg body weight) and saline (IP), respectively. Injections performed ten minute prior to PTSD and spatial memory was tested ten minutes later. Data were analyzed using SPSS-16, One-Way ANOVA and Tukey tests. Results: The platform location latency of the Desmopressin acetate+PTSD group was significantly shorter (4.24 sec) than the control group (P<0.05) and also, had significantly smaller average proximity values (33.87 cm) compared to the saline+PTSD group (P<0.05). Desmopressin acetate + PTSD spent significantly more time (21.65%) in the target zone (P<0.05). Conclusion: This study indicated that Desmopressin acetate blocks the ability of PTSD to impair spatial memory retention

The effects of cimetidine on motor activity: an evaluation the role of opioid receptors

Introduction: Effects of cimetidine (CIM) on locomotor is controversial. This study was designed to evaluate the effects of CIM on motor activity and possible roles of opioid receptors in CIM-induced decrement in locomotor activity in mice. Materials & Methods: Thirty-six male mice (25-30gr) were divided into six groups in this study. Locomotor activity was evaluated using an automated activity monitor system. CIM (50 mgkg, i.p.) was injected 25 min before testing in presence or absence naloxone (2 mg/kg, sc). Morphine (5 mg/kg, i.p) was injected 25 min before testing in the presence or absence CIM. decreased motor activity significantly. Pretreatment of or morphine did not change CIM – induced response significantly. Results: The results showed that CIM significantly decreased motor activity in mice (P=0.000). Pretreatment of nalxone did not change CIM-induced response significantly. Morphine alone did not change motor activity. Pretreatment of CIM did not change morphine-induced response. Conclusion: Data indicated that cimetidine can reduce motor activity independence from interaction with opioid receptors

Verapamil enhances the impairing effects of stress on retrieval of long-term memory in rats

Introduction: This study investigated an interaction between acute restraint stress and verapamil, as a blocker of L-type voltage sensitive channels on retrieval of long-term memory. Materials and Methods: Young adult male rats were trained in one trial inhibitory avoidance task (1mA, 1.5s footshock). On retention test given 48 hr after training, the latency to re-enter dark compartment and time spent in light chamber of the apparatus were recorded. Thirty min before retention test, the rats were exposed to a 10 min of restraint stress in a Plexiglass with or without prior treatment of verapamil (5, 10, 20 mg/kg). Results: The results showed verapamil pretreatment enhanced the impairing effect of stress on memory retrieval. The applied stress increased circulating corticosterone levels as assessed immediately after the retention test, indicating that stress–induced impairment of memory retrieval is mediated, in part, by increased plasma levels of glucocorticoids. Verapamil did not affect on this response. Conclusion: These findings indicate that acute restraint stress impair retrieval of long-term memory, and provide evidence for the existence of an interaction between stress and L-type voltage calcium channels on this process