Effects of STZ and DSP-4 on DBH-immunoreactive fibers in L4-5 dorsal horn. Representative photomicrographs of DBH-immunoreactive fibers in L4-5 dorsal horn in (A) vehicle + saline, (C) STZ + saline, (E) vehicle + DSP-4 and (G) STZ + DSP-4 rats at 6 weeks after STZ injection. Panels (B), (D), (F) and (H) are higher magnification of boxed area in (A), (C), (E) and (G), respectively. The scale bar in (A) is 50 μm and applies to (C), (E) and (G) and the scale bar in (B) is 12.5 μm and applies to (D), (F) and (H). (I) Quantification of DBH-immunoreactive fibers in L4-5 dorsal horn at 6 weeks after STZ injection. Ratio of DBH-immunoreactive pixels to the total pixel number in the dorsal horn gray matter (see Methods). Four to eleven dorsal horn samples were used for evaluating average ratio values in each rat. The mean ± SEM values of 4 rats for each experimental group are shown. *P < 0.05 (Mann–Whitney U-test) between vehicle (Veh) and STZ groups in saline-treated animals; #P < 0.05 (Mann–Whitney U-test) between saline-treated and DSP-4-treated groups in both STZ and Veh groups; NS, not significantly different.