Qom University of Medical Sciences Journal

Background and objectives Cannabinoids which are active compounds of marijuana show some pharmacological effects similar to the opioids. There are also functional interactions between both cannabinoid and opioid systems. In this study we investigated the role of cannabinoid receptors in central amygdala and its interaction with opioid system.   Methods In the present study, we investigated the effects of intraperitoneal injection of opioid drugs on response-induced by intra-amygdala (intra-Amyg) microinjection of cannabinoid agents in rats, using elevated plus-maze test of anxiety.   Results Intraperitoneal injection of morphine (3, 6 and 9 mg/kg) increased %OAT and %OAE, but not locomotor activity, showing an anxiolytic response. However, some doses of the opioid receptor antagonist, naloxone reduced %OAT and locomotor activity as well. Intra-Amyg administration of CB1 cannabinoid receptor agonist, ACPA (at the dose of 1.25 and 5 ng/rat) increased %OAT and %OAE but not locomotor activity, thus showing an anxiolytic response, which was increased by morphine (6 mg/kg, i.p.) without any interaction. Naloxone also reduced ACPA effects. Intra-Amyg administration of CB1 cannabinoid receptor antagonist, AM251 (2.5, 25 and 100 ng/rat) did not alter %OAT and %OAE but higher doses of drug (25 and 100 ng/rat) reduced locomotor activity. However, the drug in combination of morphine anxiolytic response and with naloxone decreased anxiety. Conclusion The results may indicate an anxiolytic for CB1 cannabinoid. Our results also showed that opioid system may have interaction with cannabinoid receptor in the amygdale.