Time-course change in the number of pERK-IR cells in the Vc and C1-C2 and the effect of i.t administration of PD98059 on ERK phosphorylation following subcutaneous Glu injection into the whisker pad skin. A: The number of pERK-IR cells was counted at 2, 5 and 10 min after Glu injection into the whisker pad skin. B, C and D: Photomicrographs of pERK-IR cells (B), NeuN positive cells (C) and the photomicrograph of B merged with C (D). E: Mean number of pERK-IR cells in Vc and C1-C2 five min after Glu injection into the whisker pad skin in the rats with i.t. administration of PD98059 or Veh. The arrows n B, C and D indicate pERK-IR and/or NeuN positive neurons induced by Glu injection. **: p < 0.01.