Figure 1
Attenuation of nerve injury- or intrathecal 5-HT3 receptor agonist SR57227-induced behavioral hypersensitivity by intrathecal treatment of 5-HT3 receptor antagonist Y25130. A-B: Nerve injury-induced thermal hyperalgesia (A) and mechanical allodynia (B) at 2 weeks after the left L5 spinal nerve ligation were significantly attenuated for 24 h after post-treatment of Y25130 (30 fmol, i.t.) compared with vehicle. ***, p < 0.001, **, p < 0.01, SNL + Y25130 vs. SNL + vehicle. n = 4–6 per group. C-D: SR57227 (10 pmol -1 nmol) induced significant decreases in thermal paw withdrawal latencies (PWLs) (C) and mechanical EF 50s (D) after intrathecal injection compared with vehicle saline (*, p < 0.05, n = 6 rats per group). Note that SR57227 at the 10 pmol dose produced a longer thermal hyperalgesia and mechanical allodynia lasting for 4 h; at a higher dose (10 nmol), SR57227 induced a transient hypoalgesia and at a lower dose (1 pmol) did not change thermal nociception (C). E: At 2 h time point, SR57227-induced thermal hyperalgesia was completely blocked by pretreatment of 5-HT3 receptor antagonist Y25130 (30 fmol, i.t.) but not saline, each of which was injected 30 min before the injection of SR57227 (10 pmol, i.t.) F: SR57227-induced mechanical hypersensitivity was totally reversed by pretreatment of Y25130 (30 fmol, i.t.) at 2 h after injection. *, p < 0.05, ***, p < 0.001, vs. saline + saline; #, p < 0.05, ###, p < 0.001, vs. saline + SR57227; n = 4–6 per group).