The rat trigeminal sensory nuclear complex (TSNC) was examined for Fos protein-like immunoreactive (Fos-LI) neurons induced by electrical stimulation (ES) of the lingual nerve (LN) at 2 weeks after injury to the LN or the inferior alveolar nerve (IAN). Intensity-dependent increase in the number of Fos-LI neurons was observed in the subnucleus oralis (Vo) and caudalis (Vc) of the spinal trigeminal tract nucleus irrespective of nerve injury. The number of Fos-LI neurons induced by ES of the chronically injured LN at A-fiber intensity (0.1 mA) was significantly increased in the Vo but not the Vc. On the other hand, in rats with chronically injured IAN, the number of Fos-LI neurons induced by ES of the LN at C-fiber intensity (10 mA) was significantly increased in the Vc but not the Vo. These results indicated that injury of a nerve innervating intraoral structures increased the c-Fos response of Vo neurons to A-fiber intensity ES of the injured nerve. A similar nerve injury enhanced the c-Fos response of Vc neurons to C-fiber intensity ES of a spared uninjured nerve innervating an intraoral territory neighboring that of the injured nerve. The present result show that nerve injury causes differential effects on c-Fos expression in the Vo and Vc, which may explain complexity of neuropathic pain symptoms in clinical cases.