Neuronal injury marker ATF3 in trigeminal ganglia neurons and microglial activation marker OX42 in spinal trigeminal nucleus. (A) ATF3 immunoreactivity in trigeminal ganglia neurons trended toward an increase in the primary afferent nerve neurons innervating the whisker pad of mice in the nerve trauma group. Some ATF3 was also observed in the trigeminal ganglia of the sham group. (B) Histogram showing ATF3 immunofluorescence increases moderately in week 10 after TIC nerve trauma. (C) Histogram showing cells in trigeminal ganglia positively stained for ATF3. There was an increase in ATF3 after infraorbital nerve injury but the increase was not significant. (D) OX42 immunohistochemistry in the spinal trigeminal nucleus identified only background levels of staining in the sham group. (E) Microglial activation was evident in the spinal trigeminal nucleus after infraorbital nerve trauma at the end of the 10 week experimental time course. (F) Bar graph showing the statistically significant increase in OX42 positive cells in the trigeminal nucleus after infraorbital TIC nerve trauma. *p < 0.05.