Mahnaz Rahimpour - MS student, Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran
Manizheh Karami - Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran
Sara Karimi - MS student, Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran
Abbas Haghparast - Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Mohammad Reza Jalali - Department of Pathology, School of Medicine, Shahed University, Tehran, Iran
Farzaneh Sabouni - National Institute of Genetic Engineering and Biotechnology, Tehran, Iran

Objective(s) Single injection of naloxone, a selective antagonist of morphine, prior to the drug conditioning testing was used to investigate on morphine dependence. Materials and Methods Conditioning to morphine (۲.۵-۱۰ mg/kg, s.c.) was established in adult male Wistar rats (weighing ۲۰۰-۲۵۰ g) using an unbiased procedure. Nitric oxide agents were microinjected into the central amygdala prior to naloxone-paired place conditioning testing. Results The results showed that morphine produced a significant dose-dependent place preference in animals. Naloxone (۰.۱-۰.۴ mg/kg, i.p.) injections pre-testing of the response to morphine (۷.۵ mg/kg, s.c.) caused a significant aversion at the higher doses (۰.۴ mg/kg, i.p.). This response was reversed by microinjection of L-arginine (۰.۳-۳ μg/rat, intra-central amygdala) prior to naloxone on the day of the testing. The response to L-arginine was blocked by pre-injection of NG-nitro-L-arginine methyl ester (L-NAME) (intra-central amygdala). Conclusion A single injection of naloxone on the test day of morphine place conditioning may simply reveal the occurrence of morphine dependence in rats, and that the nitric oxide in the central amygdala most likely plays a key role in this phenomenon.

Amygdala, Morphine dependence, Naloxone, Nitric oxide