Fig. 4.

Comparisons of molecules with different hydration energies suggest inward current was influenced by hydration whereas outward current was not. A–C: MET currents with either Cs⁺ (black, A) or Li⁺ (red, B) as internal and external charge carriers in response to maximal bundle deflections used to generate current-voltage plots (C). Current-voltage plots generated from A and B were fit with the equation for a single-site binding model (n shown in parentheses). Cs⁺ shows greater inward current than Li⁺ but no difference in outward current. D–F: mechanical activation curves (stimulus protocol shown at top) for cells with Cs⁺ (black, D) and Li⁺ (red, E) as the monovalent ion present extracellularly. Currents are larger and adaptation faster with Cs⁺ as the charge carrier. Gray trace in D and orange trace in E highlight the change in adaptation rate. Normalized current-displacement plots (F) show no significant difference between Cs⁺ and Li⁺ (n = 7 for Li⁺ and 6 for Cs⁺). Plots were normalized to account for reduced current with Li⁺ as the charge carrier. Current-displacement plots were fit to the equation for a double Boltzmann plot. Adaptation time constants (τ) were measured by fitting a single exponential to the current decay in response to a stimulus evoking <50% of the maximal current. Individual cell responses (G) and average values (H) show the time constant varies depending on the monovalent ion present. I: comparisons between different monovalent ions in current amplitude when extracellular Ca²⁺ was lowered to 50 μM. Values are averages (n shown in parentheses). J: plots of the percentage of cells retaining adaptation when extracellular Ca²⁺ was lowered for cells with differing extracellular monovalent ions. *P < 0.01.