Fig. 4. Aδ-fiber excitatory postsynaptic currents (EPSCs) (A ) and C-fiber EPSCs (B ) evoked in substantia gelatinosa neurons in the absence (left ) and presence (right ; where control EPSC is superimposed for comparison) of an α²agonist, clonidine (10 μm;a ), an α^2Aagonist, oxymetazoline (10 μm;b ), an α¹agonist, phenylephrine (10 μm;c ), and a β agonist, isoproterenol (40 μm;d ). Note that both of the EPSCs were depressed by clonidine and oxymetazoline but not phenylephrine and isoproterenol. Each of the records is an average of 12 traces of EPSCs; V^H=−70 mV.