Pharmacological characterization of the activation of dorsal horn neurons by Aβ-, Aδ- and C-fiber electrical stimulations. The activation was evaluated by the immunoreactivity for pERK. (a) Representative pictures of pERK signals in the ipsilateral spinal dorsal horn after electrical stimulation to the right hind paw (see Methods). The figures in the bottom of each picture indicate pERK signals, which were used for pERK quantification (see Methods). Representative pictures of spinal antagonism of the pERK signals induced by 250 or 5 Hz stimuli (b), and the results of pERK quantification (c).: vehicle (Veh; aCSF), CP-99994 (CP) (10 nmol), MK-801 (MK) (30 nmol), AP-5 (30 nmol), CNQX (10 nmol). *: p < 0.05 vs. no stimulus, #: p < 0.05 vs. vehicle. Data represent the means ± S.E.M. from experiments using at least 4 mice. Scale bar = 100 μm.