Diffuse brain injury increased microglial translocator protein 18 kDa (TSPO) receptor binding. (A) Autoradiographs of [3H]PK-11195 radioligand receptor binding to TSPO in sham, 7 day, and 28 day fluid percussion injured (FPI) rats brain (n = 3–5). [3H]PK-11195 binding showed increased TSPO protein density at 7 days post-injury in the S1BF and VPM, indicating microglial activation in these two regions. At 28 days after FPI, [3H]PK-11195 binding above sham levels was observed in the S1BF and VPM, but this was less extensive compared to 7 day FPI animals. (B, C) The quantification of [3H]PK-11195 binding by optical densities indicated a significant increase in TSPO protein density by 7 days post-FPI in both the S1BF (B) and VPM (C). By 28 days post-FPI, the TSPO protein density remained significantly elevated in the thalamus. *, p < 0.05 compared to sham-injured animals. Means are from 3–4 animals per time point.