Background: Recently, some studies have shown that minocycline may have pleiotropic biologic activities besides its antimicrobial activity. Minocycline is also an inhibitor of microglial cell activation, an effect that may contribute to its antinociceptive activity, as these cells release several mediators, including cytokines and eicosanoids, which enhance synaptic transmission in the central nervous system.
Objectives: The objective of this study is to evaluate antinociceptive activity of minocycline by tail-flick response and acetic acid-induced writhing methods.
Materials and Methods: Wistar rats of either sex weighing 180250 g and Swiss mice weighing 2530 g were used. Analgesic activity of minocycline (100 mg/kg i.p.) was evaluated and compared with tramadol (10 mg/kg i.p.) and aspirin (100 mg/kg i.p.) using acetic acid-induced writhing method and tail-flick response method of analgesia.
Results: In acetic acid-induced writhing model of analgesia, the action of minocycline (100 mg/kg i.p.) was significantly more than the control group, but it was less when compared to aspirin. Furthermore, in tail-flick model of analgesia, it showed significant analgesic activity but was less than that of aspirin and tramadol.
Conclusion: Minocycline possesses analgesic activity. However, further studies need to be carried out to evaluate its analgesic activity.
Key words: Antinociception; Minocycline; Acetic Acid-induced Writhing; Tail-flick
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