Figure 4. Vesicle fusion was not significantly altered by changes in vesicular glutamate loading. A: Exocytotic increase in membrane capacitance (C_m) evoked by stimulation of a cone lacking supplementary glutamate in the cytosol. Access resistance was not significantly altered (bottom trace). B: Exocytotic capacitance increase evoked by stimulation of a cone with 40 mM glutamate added to the pipette solution. C: Exocytotic capacitance increase evoked by stimulation of a cone lacking cytosolic glutamate and following pretreatment with the vesicular ATPase inhibitor concanamycin A (CMA, 3.5 μM) for 1 h. D: Exocytotic increases in membrane capacitance evoked by depolarizing stimulation of cones (25 ms, −70 to −10 mV) without supplemental glutamate (n=7), with 40 mM glutamate added to the patch pipette (n=6), and after >1 h incubation in concanamycin A with no glutamate in the patch pipette (n=6). Error bars show SEM.