Nitric Oxide Implicates c-Fos Expression in the Cuneate Nucleus Following Electrical Stimulation of the Transected Median Nerve

In this study, we investigated whether nitric oxide (NO) modulated injury-induced neuropeptide Y (NPY) releasing and c-Fos expression in the cuneate nucleus (CN) after median nerve transection (MNT). We first examined the temporal changes of neuronal nitric oxide synthase (nNOS) expression in the dorsal root ganglion (DRG) and CN after MNT. Following MNT, the amounts of nNOS-like immunoreactive (nNOS-LI) neurons in the DRG and CN significantly increased as compared with those of the sham-operated rats. Furthermore, 4 weeks after MNT, the increases of nNOS-LI neurons in the DRG and CN were attenuated by pre-emptive lidocaine treatment in a dose-dependent manner. Finally, 4 weeks after MNT, pre-stimulation administration of L-NAME (Nx-Nitro-L-arginine methyl ester) or 7-NI (7-nitroindazole) suppressed the amount of NPY release from the stimulated terminals and thus attenuated c-Fos expression in the CN. Our data implied that NO would modulate neuronal activity in the DRG and CN both after MNT.