Fig. 3. Concentration dependence of axonal Na+channel ( open symbols ) and flicker K+channel block ( filled symbols ) by R(+)-bupivacaine ( circles ) and S(−)-bupivacaine ( squares ). Solid lines represent fits to the data points under the assumption of a single binding site ( equation 1), the dotted line represents a fit under the assumption of two independent binding processes ( equation 2). Crosses mark IC50values.