Abstract
Fos is a good marker for histological mapping of activated neurons in the central nervous system. However, its expression in the primary sensory neurons (PNS) is low and, therefore, cannot be used as a marker for activated PNS. In this study, we examined if phosphorylated nuclear factor kappa B (pNFkB) is a suitable marker for activated PNS. Male C57BL6 mice were injected with 20 μl of 10 mM capsaicin subcutaneously in the right hind paw under pentobarbital anesthesia. They were perfused from the left cardiac ventricle with 4% lidocaine 1 min, 5 min, or 15 min after the injection. Frozen sections of L4 DRG were triple-immunostained for pNFkB, capsaicin receptor (VR1), and neurofilament 200. At 1 min, pNFkB was observed in the nucleus of a subset of DRG neurons only in the injected side. At 5 min and 15 min, pNFkB-positive neurons appeared also in the contra-lateral DRG. The appearance of pNFkB-positive neurons in the contra-lateral side seems to be due to systemic spread of capsaicin because more than 90% of pNFkB-positive neurons were also positive for VR1 at all time points. In a separate group of mice, the right hind paw was electrically stimulated for 10 min, and their L4 DRG was examined for pNFkB. PNFkB-positive neurons were found only in the stimulated side and 45% of them were positive for VR1. These results suggest that pNFkB is a suitable marker for activated PNS. [J Physiol Sci. 2007;57 Suppl:S106]
