A and B, photomicrographs of the NTS after vehicle (A) or PD98059 (B) i.t. administration in the rat with whisker pad skin capsaicin stimulation, respectively. C and D, mean number of pERK-LI neurons in the NTS, Vc and Pa5 in the rats with capsaicin injection to the whisker pad skin (C) or lingual muscle (D) following PD98059 i.t. administration compared to that after vehicle administration. E, effect of the i.t. administration of PD98059 on the number of swallows in the rats with capsaicin injection to the whisker pad skin or lingual muscle compared to that following vehicle administration. cc: central canal. *P < 0.05, **P < 0.01.