Abstract

Introduction: Nucleus accumbens shell is one of the most important effecting areas of morphine in terms of inducing euphoria and reward. GABAergic system, especially GABA-B receptors, has an important role in modulating euphoric effects of morphine. In this research, effect of injecting baclofen drugs (GABA-B receptor agonist) and CGP35348 (GABA-B receptor antagonist) into nucleus accumbens shell on inducing tolerance resulted from morphine was done using Conditioned Place Preference (CPP) method in Wistar rats with mean weight of 230±20 g. Methodology: Five days after the surgery and cannulation, different amounts of morphine were subcutaneously (S.C.) injected and conditioning stages were done using unbiased method. The obtained results showed that subcutaneous injection of morphine (0.5-7.5 kg/mg) could make conditioned preference place dose-dependent. In the current study, injection of baclofen and CGP35348 into nucleus accumbens on expression of conditioned place preference was studied in morphine-tolerant rats. Results: Injection of baclofen with doses of 1.5 and 12 μg/rat reinforced expression of conditioned place preference in morphine-tolerant rats; but, in case of CGP35348, injection of this drug did not induce any specific effect on expression of conditioned place preference in morphine-tolerant rats. Discussion: The resulted findings showed probable capability of the studied receptor in this research for suppressing reward results of morphine using baclofen in response to tolerance. In general, it seems that stimulation or inhibition of GABA-B receptors in nucleus accumbens shell plays an important role in expression of conditioned place preference resulted from morphine in morphine-tolerant rats. © 2014 AENSI Publisher All rights reserved.