• Endocannabinoids reduce the expression of the alpha-3 subunits of the GABAA receptors of the basolateral amygdala during formalin-induced inflammatory pain modulation in adult male rats
  • Fateme Naseri1,1,* , Roghaieh Khakpay,2 Fatemeh Khakpai,3 Dariush Shanehbandi,4
    1. 1. Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran.
    2. 1. Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran.
    3. 2. Department of Physiology, Faculty of Medicine, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran.
    4. 3. Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran


  • Introduction: The basolateral amygdala (BLA) integrates cognitive and pain information and transmits it to the central nucleus of the amygdala, which is the origin of the descending pain modulatory pathway. The role of the BLA endocannabinoid system has been well shown in nociceptive processing. This system induces analgesia through its type 1 receptors and the GABAergic system inhibition. Therefore, this study aimed to investigate the gene expression changes of α2, α3, and β2-subunits of the GABAA receptors of the BLA in the antinociceptive role of the endocannabinoid system following the inflammatory pain induction.
  • Methods: In this study, the BLA tissue samples of male Wistar rats were used. 28 Male rats (220-270 grams) were randomly divided into four groups of seven rats, including the control (intact animals), formalin (formalin test in intact animals), DMSO (intra-BLA injection of DMSO 10 %), and AM251 (intra-BLA injection of AM251 50 ng/µl) groups. Following the formalin test, tissue samples were removed and stored in a -80 ℃ freezer. Gene expression of α2-, α3-, and β2-subunits of the GABAA receptors was evaluated by qRT-PCR technique.
  • Results: Data analysis showed that formalin injection into the left paw only decreased the gene expression of the α3 subunit of the GABAA receptor compared to the control group (P<0.05). Also, following the inflammatory pain induction, the injection of AM251 into the right BLA significantly decreased the gene expression of the α3 subunit of the GABAA receptor compared to the control group (P<0.05). Still, it had no significant effect on the gene expression of the α2 and β2-subunits of this receptor.
  • Conclusion: The findings of this study suggest that the presence of the α3 subunit in the heteropentameric structure of the GABAA receptor is probably necessary for the endocannabinoid system-induced analgesia in the basolateral amygdala.
  • Keywords: Endocannabinoids, inflammatory pain modulation, GABAA receptors, Formalin