Fig 2. Membrane currents evoked by activation of hetrotrimeric G proteins in wild-type cell lines.

(A) The activator GTP-γ-S was applied intracellularly by perfusion via the patch pipette, at a concentration of 100 μM. In all three cell lines tested, GTP-γ-S evoked an inward current with a slow time course; control recordings obtained with GTP (grey traces) remained flat. (B) Bar-graph comparing the average peak amplitude of the GTP-γ-S-elicited current in Neuro2QA, CHO-K1, and HEK 293 cells (black bars; error bars indicate standard deviation); HEK cells consistently produced a larger response. For control cells of each type (grey bars) the change in holding current between the beginning and end of the recording period was measured.