Fig. 7. Time course for immunostaining density of substance P (SP) and calcitonin gene-related peptide (CGRP) in the superficial dorsal horn. (A ) Quantitative immunohistochemistry demonstrates expression increases for SP at days 3 and 7 from animals injected with dibutyltin dichloride for comparison to the other groups (*P < 0.05). (B ) The CGRP immunostaining showed a trend of increased density at all time points, but the increase did not reach statistical significance. Error bars denote SEM.