morphine reduces expression of trpv1 receptors in the amygdala but not in the hippocampus of male rats

background: chronic use of opioids usually results in physical dependence. the underlying mechanisms for this dependence are still being evaluated. transient receptor potential vanilloid type 1 (trpv1) are important receptors of pain perception. their role during opioid dependence has not been studied well. the aim of this study was to evaluate the effect of morphine-dependence on the expression of trpv1 receptors in the amygdala and ca1 region of the hippocampus. methods: this study used four groups of rats. two groups of rats (morphine and morphine+naloxone) received morphine based on the following protocol: 10 mg/kg (twice daily, 3 days) followed by 20, 30, 40 and 50 mg/kg (twice daily), respectively, for 4 consecutive days. another group received vehicle (1 ml/kg) instead of morphine given using the same schedule. the morphine+naloxone group of rats additionally received naloxone (5 mg/kg) at the end of the protocol. the control group rats received no injections or intervention. the amygdala and ca1 regions of the morphine, saline-treated and intact animals were isolated and prepared for real-time pcr analysis. results: administration of naloxone induced withdrawal signs in morphine-treated animals. the results showed a significant decrease in trpv1 gene expression in the amygdala (p<0.05) but not the ca1 region of morphine dependent rats. conclusion: trpv1 receptors may be involved in morphine-induced dependence.