Anti-nociceptive Mechanisms of Testosterone in Unilateral Sciatic Nerve Ligated Male Rat

 BACKGROUND: Neuropathic pain is a chronic condition which is mediated by complex mechanisms exerted by the release of nerve neurotransmitter. A correlation exists between the sex hormones and neuropathic pain, however many aspects of this correlation still remain unclear. OBJECTIVES: The aim of the current study was to determine the anti-nociceptive activity of testosterone and its interaction with the opioidergic, GABAergic, and dopaminergic receptors in sciatic nerve-ligated male rats. METHODS: In this study, ۱۷۰ adult male rats were randomly allocated into the ۴ experimental groups following the sciatic nerve ligation. In the experimental group ۱, the animals were injected intraperitoneally (i.p.) with saline, testosterone (۱۰ and ۱۵ mg/kg), and morphine (۵ mg/kg), and ۳۰ minutes later with formalin into the plantar surface of the right paw. In the experimental group ۲, the animals were injected with saline, testosterone (۱۵ mg/kg), nalox-one (۲ mg/kg), and testosterone (۱۵ mg/kg)+naloxone (۲ mg/kg). In the groups ۳ and ۴, flumazenil (۵ mg/kg) and yohimbine (۲ mg/kg) were injected instead of naloxone. Then, the time spent for paw licking was monitored for the first and second phases after the formalin injection. RESULTS: According to the results, the injection of testosterone in a dose dependent manner decreased the time of licking and biting in the injected paw compared to the control group (P<۰.۰۵). Likewise, pretreatment with na-loxone or flumazenil significantly decreased the anti-nociceptive effect of testosterone (P<۰.۰۵). While pretreatment with yohimbine significantly increased the anti-nociceptive effect of testosterone (P<۰.۰۵). CONCLUSIONS: These results suggested testosterone has an anti-nociceptive activity and this effect is mediated by the opioidergic, GABAergic, and dopaminergic receptors in the sciatic nerve-ligated male rat.

کلیدواژه ها:

Anti-nociceptive ، Dopaminergic ، GABAergic ، rat ، Sciatic nerve injury ، Testosterone