Veterinary Research Forum
Vet Res Forum

Thioperamide-induced Antinociception is Mediated through Endogenous Opioid System in the Dentate Gyrus of Adult Rats

Document Type : Original Article

Authors

Emad Khalilzadeh 1
Esmaeal Tamaddonfard 1
Amir-Abbas Farshid 2
Amir Erfanparast 1

1 Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

2 Department of Pathobiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

Abstract
The present study investigated the effects of intra-dentate gyrus microinjection of naloxone (an opioid antagonist) and thioperamide (an antagonist of histamine H3 receptors) in the formalin test in rats. Subcutaneous injection of formalin (50 μl, 2.5 %) in the ventral surface of right hind paw produced a biphasic pattern (first phase: 0-5 min and second phase: 15 - 60 min) of licking/biting and shaking of the injected paw. Intra-dentate gyrus microinjections of thioperamide (2 and 4 μg) significantly (P < 0.05) suppressed the pain responses. Microinjections of naloxone (1, 2 and 4 μg) alone into the dentate gyrus non-significantly increased the intensity of pain. Pretreatment with naloxone (4 μg) significantly (P < 0.05) reversed the antinociceptive effect of thioperamide (4 μg). The results indicated that at the level of the dentate gyrus, blockade of histamine H3 receptors with thioperamide produced an analgesic effect. This thioperamide-induced antinociception may be mediated through the endogenous opioid system.

Keywords

Dentate gyrus
Formalin-induced pain
naloxone
Thioperamide
Rats
Veterinary Research Forum
Volume 1, Issue 3 - Serial Number 3
December 2010
Pages 166-173

  • Receive Date 26 December 2012

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