Fig. 5.
Degree and distribution of phosphorylated extracellular signal-regulated kinase (pERK) expression in the lumbar spinal cord after plantar incision. (A) Representative pERK staining with double labeling of ipsilateral dorsal horn (i, scale bar = 100 μm) and high-power view (ii) confirming expression of p-ERK (green, iii) in neurons (NeuN, red, iv) 15 min after commencement of plantar incision. (B) Double-labeling of sections at 15 min (i, ii) or 24 h (iii, iv) demonstrated coexpression of pERK with NeuN but not the microglial marker ionized calcium-binding adaptor molecule-1 (Iba1) at both time points (scale bar = 50 μm). (C) Counts of pERK-immunoreactive positive cells (pERK-ir) in adult-only (IN) and previous neonatal plus adult incision (nIN-IN) groups are shown 15 min after the commencement of incision (n = 10 per group) and at 24 h (n = 4 per group). For each animal, the cell count was averaged from 10 randomly selected lumbar cord (L4/5) sections. Cell counts were significantly higher at 15 min versus 24 h (P < 0.001) but did not differ between IN and nIN-IN groups at either time point (two-way ANOVA followed by Bonferroni post hoc comparisons). (D) The degree and distribution of pERK-IR cells 15 min after incision was quantified from serial lumbar sections and mapped against spinal length. The average cell count per five serial sections from L2-5 cord was calculated for each animal. Group values are plotted from cephalad to caudal and showed a similar pattern in both IN and nIN-IN groups. Data points = mean ± SEM, n = 10 animals per group. (E) The distribution of pERK staining correlates with the segmental distribution of afferent fibers from the medial and lateral plantar nerves (redrawn from Molander C, Grant G: Laminar distribution and somatotopic organization of primary afferent fibers from hindlimb nerves in the dorsal horn. A study by transganglionic transport of horseradish peroxidase in the rat. Neuroscience 1986; 19:297–312.44 Reproduced with permission from Elsevier. Adaptations are themselves works protected by copyright. So, to publish this adaptation, authorization must be obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation). (F) The area under the curve (AUC) for cell counts versus spinal length was calculated for L2/L3 and L4/L5, and did not differ between treatment groups (nIN-IN vs. IN P > 0.05, one-way ANOVA). Bars = mean ± SEM, n = 10 per group.