Effect of yohimbine on NA oxidation currents and neurogenic constriction of MA and MV A, recordings of oxidation current and constriction in a MA in the absence and presence of yohimbine (1 μm). B, oxidation current and constriction in a MV with and without yohimine. Yohimbine increased the current but not constriction in MA. Yohimbine had little effect on the oxidation current in MV but it reduced the constriction. Bars under the current traces indicate the period of nerve stimulation (60 pulses, 0.3 ms pulse duration.) C, percentage increase in NA oxidation currents in MA and MV in the presence of yohimbine. D, frequency–response curves for vasoconstriction in MA and MV in the absence (control) and in the presence of yohimbine. #Significantly different from control (P < 0.05). Data are means ±s.e.m.