Figure 3.

OHC Endogenous Ca²⁺ Buffer Assayed with Perforated Patch

(A) MT currents recorded with an intracellular solution containing 1 mM EGTA as the Ca²⁺ buffer, in Na⁺, 1.5 mM Ca²⁺ saline (middle), and during local perfusion with K⁺, 0.02 mM Ca²⁺ endolymph (bottom).

(B) MT currents under perforated-patch in Na⁺, 1.5 mM Ca²⁺ (middle) and during local perfusion with K⁺, 0.02 mM Ca²⁺ endolymph (bottom). Top traces are the bundle stimuli evoked by a piezoelectric-driven glass probe.

(C) MT current, I, scaled to its maximum value I_MAX, versus hair bundle displacement for recording with EGTA. I_MAX = 0.90 nA (1.5 Ca²⁺) and 1.45 nA (0.02 Ca²⁺).

(D) I/I_MAX, versus hair bundle displacement for perforated patch recording. I_MAX = 0.99 nA (1.5 Ca²⁺) and 1.38 nA (0.02 Ca²⁺) and 0.62 nA (1.5 Ca²⁺ wash). For both conditions, low Ca²⁺ endolymph increased the fraction of MT current on at rest, but this was much smaller with EGTA (0.08) than with perforated patch (0.43).