Fig. 1.

SR Ca²⁺ release activates Cl⁻ currents in zebrafish skeletal muscle. a–c Representative recordings from zebrafish myotubes elicited by 200-ms depolarising test potentials between −50 and +80 mV. a Robust outward currents (left traces) and intracellular SR Ca²⁺ release (right traces) were recorded from normal myotubes under standard external solution containing 165 mM Cl⁻. b In contrast, under Cl⁻ free conditions normal myotubes displayed only marginal currents (I = 2.99 ± 0.20 pA pF⁻¹ at +80 mV, n = 5) (left traces) but unaltered (P > 0.05) SR Ca²⁺ release ((ΔF/F₀)_max = 3.01 ± 0.24, n = 5) (right traces). Scale bars, (left) 50 ms (horizontal), 40 pA pF⁻¹ (vertical); (right) ∆F/F₀ = 1 (vertical). c Representative recordings from relaxed zebrafish myotubes with standard external solution containing 165 mM Cl⁻ showed neither considerable outward currents (left traces) nor SR Ca²⁺ release (right traces), identifying this outward current as SR Ca²⁺-release-activated Cl⁻ current. d Left graph, plots of current–voltage relationship under standard Cl⁻ conditions (165 mM) from normal (I = 114.55 ± 9.81 pA pF⁻¹ at +80 mV, n = 5) and relaxed myotubes (I = 2.70 ± 0.02 pA pF⁻¹ at +80 mV, n = 5), and (right graph) voltage dependence of maximal Ca²⁺ release from normal ((ΔF/F₀)_max = 3.23 ± 0.45, n = 5) and relaxed ((ΔF/F₀)_max = 0.11 ± 0.05, n = 5) myotubes. Data are presented as mean ± s.e.m.; P determined by unpaired Student’s t-test