Fig. 5.

NP_o of reconstituted SR channels is regulated by Ca²⁺ levels at the cytosolic side of the channel. Averaged NP_o from the prevalent SR channel phenotype in response to changes in free Ca²⁺ in the solution bathing the bilayer cis side. Unitary currents were evoked at V = +15 mV and variant amounts of Ca²⁺ in the cis solution. NP_o was obtained as described for Fig. 2. *Different from 0.1 μM Ca²⁺, P < 0.05; **different from 0.1 μM Ca²⁺, P < 0.01; ***different from 0.1 μM Ca²⁺, P < 0.01 (n = 8). Inset shows unitary conductance (γ) obtained in 10 μM Ca²⁺ vs. 300 mM Cs⁺ and indicates that Ca²⁺ modulation of NP_o is accompanied by a decrease in conductance. **Different from in γ in Cs⁺, P < 0.01 (n = 8).