Fig. 2

Mechanical allodynia and histological changes following SNL. a Paw withdrawal threshold over time. The paw withdrawal thresholds were observed on the 3rd, 5th, 7th, and 14th day post spinal nerve ligation (SNL). The development of neuropathic pain was confirmed with decreased withdrawal thresholds of the rats from group C and E compared to the group S throughout the observation periods (p < 0.001). The withdrawal thresholds are significantly higher in rats from group E than in those from group C from the 5th day post SNL (p < 0.001). *p < 0.05 compared with group C. b Hematoxylin and eosin staining in the the spinal cord sections. Sections from group S (I, IV) show only a small number of lymphocytes (small circles), normal oligodendrocytes (arrows) with prominent perinuclear halos, and vacuoles containing poorly stained material (stars). Sections from group C (II, V) show lymphocytes infiltration and many oligodendrocytes localized in the substantia gelatinosa of the posterior gray horn. Sections from group E (III, VI) show a reduced number of lymphocytes and oligodendrocytes than those in group C. Group S, Sham-operated; Group C, saline-treated after SNL; Group E, nefopam-treated after SNL. Original magnification, X200. →, Oligodendrocytes; o, Lymphocytes; *, Vacuoles