The inhibition of Nucleus accumbens cholinergic receptors decreased memory retention in rat

It is well known that morphine influence learning and memory processes. The Nucleus accumbens (N.ac) which has an important role in reward participates in morphine-induced impairment of memory retention. Considering the cholinergic system is involved in the effects of morphine on learning and memory, in the present study, the effects of intra-N.ac injections of acetylcholine receptor antagonists alone or with morphine on memory retention and morphine-induced memory has been investigated in rats. In this original research animals were bilaterally cannulated in the N.ac and a step-through passive avoidance task was used for the assessment of memory retention. Post-training subcutaneous administration of morphine dose dependently decreased the learning and induced amnesia. The administration of the same dose of morphine as pre-test treatment induced state-dependent learning. Pre-test intra- N.ac administration of atropine, scopolamine and mecamylamine in different doses alone cannot affect on memory retention. While, pretest intra- N.ac injection of these drugs before the administration of morphine dose dependently inhibited morphine state-dependent learning. The level of statistical significance was set at p<0.05. The processes of learning in animals can be affected by morphine and the opioids produce state-dependent learning. Moreover, it can be concluded that inactivation of the muscarinic and nicotinic acethylcoline receptors in the N.ac are involved in mediating morphine state-dependent learning.