Figure 6. Expression of G-protein β₁γ₂ dimers strongly alters the voltage-activated Ca²⁺ transient in skeletal muscle fibres.

A, representative indo-1 [Ca²⁺] traces from a control (left panel) and from a Gβ₁γ₂ dimer-expressing fibre (right panel) in response to depolarizing steps of increasing duration to +10 mV from a holding potential of −80 mV. The inset in each panel shows the corresponding mean (continuous traces) ±s.e.m. (grey shading) [Ca²⁺] traces. B–D, corresponding mean ±s.e.m. values of peak change in [Ca²⁺], time constant (τ) of [Ca²⁺] decay after the end of the pulse and final change in [Ca²⁺] level, respectively, measured from 10 control fibres and 6 Gβ₁γ₂ dimer-expressing fibres. The peak change in [Ca²⁺] was reduced by 43% (P= 0.0003) (20 ms depolarizing step) in the Gβ₁γ₂-expressing fibres. Values for the final change in [Ca²⁺] level were from the exponential fits. When not visible, errors bars are smaller than the mean dot.