Figure 3.

Kv2.1 enhancement of release does not arise from differences in membrane potential or intracellular free Ca²⁺. a, Membrane potential, measured from GFP-expressing cells using the whole-cell current clamp. Increased depolarizations were observed when cells were bathed in 70 mm KCl solution (KCl) compared with control solution (rest); however, membrane potentials were similar for Kv2.1- and empty vector-transfected cells (control; 15 and 11 cells per group, respectively). b, Both resting and evoked Ca²⁺ levels are similar in Kv2.1-transfected and control cells. Left, In a single cell, intracellular Ca²⁺ concentration ([Ca²⁺]_i; filled circles) and depletion of proANF-GFP fluorescence (fluorescence; open circles) were measured during two extracellular applications of 70 mm KCl (bars). An increased rate of fluorescence depletion indicating proANF-GFP release coincides with the rise in intracellular Ca²⁺. Right, Bar graph showing that resting [Ca²⁺]_i (left bars) and peak values during KCl application are similar for Kv2.1 and control cells (n = 13 and 14, respectively).