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.


CONCLUSIONS
TRPV1 receptors may be involved in morphine-induced dependence.
Physiology-Pharmacology Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
Elham
E
Hakimizadeh
Immunology of Infectious Diseases Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
Mohammad
M
Kazemi Arababadi
Physiology-Pharmacology Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
Ali
A
Shamsizadeh
Physiology-Pharmacology Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran;
Mohammad
M
Allahtavakoli
Department of Physiology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran;
Mohammad Ebrahim
ME
Rezvani
Pharmaceutical Research Center, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
Ali
A
Roohbakhsh
Amygdala; CA1 region; Morphine; Rats; Vanilloid receptor subtype 1