Figure 5. G protein involvement in muscarinic suppression of erg.

A, muscarinic suppression of current in control cells and cells preincubated with the G_i/o inhibitor N-ethylmaleimide (NEM; 50 μm) for 2 min. The test pulse protocol for this and subsequent experiments is as in Fig. 1. B, initial density of current in cells overexpressing constitutively active forms of G_q, G_s or G₁₃ (caG_q, caG_s or caG₁₃) or RGS2. *P≤ 0.05 and **P≤ 0.005 indicate significant difference from controls. C, percentage suppression in cells overexpressing dominant-negative G₁₃ or G_q (dnG₁₃, dnG_q), or RGS2. Individual observations are shown as open circles. *P≤ 0.05 and ***P≤ 0.0005 indicate significant difference from controls. D, E and F, representative time courses of test currents during inhibition by oxo-M in cells cotransfected with the indicated genes. For RGS2, the example is representative of 10/13 cells.