Fig. 4.
In the presence of the nonhydrolyzable analog of GTP, GTPγS, 1S,3R-ACPD irreversibly activates ICAN, because intracellular perfusion with the G-protein inhibitor GDPβS prevents the activation of ICAN. A-a, Membrane current and conductance changes evoked by a first application of 1S,3R-ACPD (200 μm, 2 min,VH = −60 mV) after 20 min of cell dialysis with 500 μm GTPγS. Note thatICAN becomes irreversible in the presence of GTPγS. A-b, Membrane current and conductance changes evoked in the same cell by a second application of 1S,3R-ACPD (200 μm, 2 min,VH = −60 mV) after 40 min of cell dialysis with 500 μm GTPγS. Note that, in the presence of GTPγS, a second application of 1S,3R-ACPD fails to evoke a subsequent response. B, Mean I/V relations of the CAN currents obtained in the same cell by two successive 1S,3R-ACPD applications performed 20 min (•) and 40 min (○), respectively, after cell dialysis with 500 μm GTPγS (n = 5; paired data).C, Mean I/V relations of the CAN currents obtained by two successive 1S,3R-ACPD applications in the same cell before (•) and after (○) pipette–whole-cell perfusion with 500 μm GDPβS (n = 7; paired data).