Background: 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.

Materials and Methods: 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 .

Results: 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 .

Conclusion: 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.

Background: because of the side effects of chemical drugs, using plant drugs was considered during recent decades. Based on previous studies, various concentrations of plant extracts can reduce ileum contraction caused by KCl and carbachol. Therefore, in this study, the role of muscarinic receptors in anti-spasmolytic activity of hydroalcohlic extract of parsley(petroselinum crispum)seed in adult male rat's ileum was investigated.

Materials and Methods: The distal part of Wistar rat’s ileum was separated and its contractions were recorded under 1 gr stretching and 37^oC temperature in the bathroom containing the solution of Tyrode by Isotonic method. The ileum tissue was inserted in separately in first group affected by KCl and parsley seed, in the second group affected by KCl and carbachol with concentration 10^-2 mg/ml and after that parsley seed, the third group affected by carbachol with concentration 10^-2 mg/ml and then the extraction of parsley seed and the fourth group affected by scopolamine with concentration 10^-3 M and after that KCl and then the extraction of parsley seed.

Results: Non-cumulative concentrations of extract reduced the ileum contraction caused by KCl (60mM) in a concentration-dependent form (p<0.001). There was a significant difference between the effect of extract in the presence of carbachol and extract concentration 0.2 mg/ml (p<0.01). There was no significant difference between the effect of extract in the presence of carbachol without stimulating tissue by KCl (60mM) with extract concentration 0.2mg/ml (p<0.05). There was no significant difference between the effect of extract in the presence of scopolamine with extract concentration 0.2mg/ml(p<0.05).

Conclusion: This study showed that the hydroalcholic of parsley seed extract has a relaxatory effect on rat’s ileum. Carbachol with KCl has a synergistic effect on smooth muscle contraction of the ileum wall and muscarinic receptors do not involve in the inhibitory function of parsley seed extract.