Antinociceptive effect of spirocyclopiperazinium salt compound LXM-15 via activating peripheral α7 nAChR and M4 mAChR in mice

Abstract The aim of this study was to evaluate the antinociceptive effects and potential mechanisms of the spirocyclopiperazinium compound LXM-15. We found that LXM-15 produced significant antinociceptive effects in a dose- and time-dependent manner in mice. The maximum inhibition ratio was 70% in the acetic acid writhing test; the effect started at 1.0 h, peaked at 2.0 h with the MPEs of 61%, and persisted 3.5 h in the hot-plate test; LXM-15 reduced the time spent licking or biting the injected paw remarkably with inhibitions of 53% in formalin test. LXM-15 did not affect motor coordination, spontaneous activity, body temperature, heart rate, or liver enzyme activity, the LD 50 values was 616.26 μmol/kg. The antinociceptive effect of LXM-15 was blocked by mecamylamine, hexamethonium, atropine or atropine methylnitrate, and was also blocked by MLA, tropicamide. In contrast, the effect was not blocked by naloxone. Meanwhile, competition receptor binding assays showed LXM-15 can bind to α7 nAChR or M4 mAChR. Our studies show that LXM-15 may be via activating peripheral α7 nicotnic and M4 muscarinic receptors, resulted in antinociceptive effects.