Figure 5

TMJ inflammation induces microglial activation in the spinal trigeminal nucleus. (A, C) Densitometric analysis of Iba1 immunoreactivity (number of immuno-positive pixels, see Methods) showing a significant increase in Iba1 immunoreactivity in the ipsilateral side of both the trigeminal subnucleus caudalis in the medulla oblongata (delimited by the dotted line; A) and the dorsal horn of the cervical spinal cord (C) 72 h after CFA injection. The mean values of pixel intensity have been normalized to the values obtained from the contralateral side of saline injected rats, set to 1.0. Since no significant differences between saline-injected rats at 24 h and 72 h have been observed, data have been pooled together, and shown here as "saline". ** p < 0.01 compared to the contralateral side; one-way ANOVA. (B-B'', D-D'') Resting microglial cells (i.e., ramified cells with fine processes) were detected in the contralateral side of the trigeminal subnucleus caudalis (B') and of the cervical dorsal horn (D'), whereas activated microglial cells (i.e. cells with thicker ramifications) were observed ipsilaterally (B'', D''). Scale bars: 20 μm.