Effects of Olanzapine on the Acquisition and Expression of Morphine-Induced Behavioral Sensitization in Mice
Trauma Monthly: 10 (4); 263-270 Article Type: Research Article
J, et al. Effects of Olanzapine on the Acquisition and Expression of Morphine-Induced Behavioral Sensitization in Mice,
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Objective: In this study, effects of different doses of olanzapine as a dopamine receptor antagoninst on the acquisition and expression of morphine-induced behavioral sensitization in male N-MARI mice (20-30 g) were investigated. Materials and Methods: Sensitization was induced by single injection of morphine (5 mg/kg) in three consecutive days followed by five days resting. On the 9 th day of the experiments, the sensitization was assessed in animals by a single injection of very low dose of morphine (0.5 mg/kg). Olanzapine was administered during or after induction of morphine sensitization. Then, the sensitization were tested in the animals. In order to evaluate the effects of the drugs on locomotor activity, morphine and olanzapine were administered to the animal in a pilot study. Results: Administration of morphine (10 and 20 mg/kg), induced a significant activity in the animals. On the other hand, administration of olanzapine (1, 2.5 and 5 mg/kg) produced a significant hypoactivity in the animals. Injection of the same olanzapine (1, 2.5 and 5 mg/kg) 20 min before the morphine (5 mg/kg) administration in the traning days, caused a significant decrease in locomotor activity in animals, i.e. reduced the acquisition of morphine-induced behavioral sensitization. Injection of olanzapine (1, 2.5 and 5 mg/kg) in the test day, 20 min before morphine (1 mg/kg) administration also reduced the locomotor activity in the animals in a dose-independent manner, i.e. reduced the expression of morphine-induced behavioral sensitization. Conclusion: It can be concluded that olanzapine may inhibit locomotor activity in mice and also acquisition and expression of morphine induced behavioral sensitization in male mice as well.
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