Fig. 2. Uncaging of GTP--S increases the relative K⁺ conductance of the membrane. (A) Effects of Leydig neuron stimulation (LS) before and after a UV pulse (UV) to uncage GTP--S on the membrane potential. After the membrane hyperpolarization following uncaging of GTP--S, LS had no additional effect on the membrane potential, while raising the extracellular K⁺ concentration from 4 to 10 mmol l^–1 evoked a large depolarization. The inset shows the effect of LS and UV pulses on a non-injected cell. (B) Effects of 3 µmol l^–1 myomodulin (MMHir) and 10 mmol l^–1 K⁺ before and after a UV pulse uncaging GTP--S on the membrane potential. (C–E) The membrane depolarization induced by 10 mmol l^–1 K⁺ is larger (C,D), and faster rising (C,E), after uncaging of GTP--S, indicating an increased relative K⁺ conductance. ^*P<0.05. N represents the number of experiments.