Figure 7

Erythropoietin (EPO) administration enhances the expression of the erythropoietin receptor (EpoR) in the brainstem of traumatic axonal injury with hypoxia (TAI + Hx) rats. (A) In the corpus callosum, TAI rats had a significant elevation in EpoR numbers over sham at 1,7 and 14 days, with similar numbers observed in TAI + EPO rats over this time course. (B) TAI + Hx and TAI + Hx + EPO treatments both resulted in increased numbers of positive cells at 1 day compared to sham, with both groups peaking at 7 days before returning to sham levels at 14 days. (C) TAI and TAI + EPO rats showed a similar expression pattern of EpoR in the brainstem at 1 d, however at 7 d, TAI + EPO rats had a substantial increase in the number of cells staining positively for EpoR. (D) No increase in EpoR positive cells was observed in the pyramidal tracts at 1 d after TAI + Hx; however in these rats, EPO administration induced a significant increase in EpoR expression. At 7 d, the number of EpoR-positive cells increased in TAI + Hx similarly to TAI + Hx + EPO. Letters matched to letter with apostrophe indicate a significant difference, P <0.05; 2-way ANOVA with post-hoc Bonferroni test. Data expressed as mean ± SEM, n = 6/group. *(E) Photomicrograph demonstrating low level of EpoR expression in the pyramidal tracts after sham surgery, a mild increase in TAI + Hx (F), and a significant increase in EpoR-positive cells in TAI + Hx + EPO rats (G). Scale bar = 100 μm.