Fos expression in the trigeminal sensory nuclei after a chemical lesion of the lower lip mucosa

C-fos containing neurons were investigated in the trigeminal sensory nuclear complex and in the dorsal horns of the cervical spinal cord (C1-C2) of the rat after a chemical noxious stimulus was applied to the lower lip mucosa. Numerous labelled neuronal nuclei were detected in the dorsolateral area of the caudal half of the trigeminal nucleus interpolaris, and in Rexedʼs laminae I-II0 of the dorsomedial area of the trigeminal nucleus caudalis and rostral C1. A few c-fos-labefled neurons were observed in laminae IIi and V. No Fos expression was detected in the trigeminal oral and principal nuclei.