Fig. 3. GTPγS decreases the magnitude and increases the P2/P1 ratio of N-type Ba²⁺currents in SH-SY5Y cells. Current traces were recorded at various membrane potentials using the voltage protocol described in Fig. 2(inset ). A family of current traces for three different cells, in the absence (A ) and presence of 120 μm (B ) and 200 μm (C ) GTPγS are shown for 0, +10, and +20 mV. (D ) The P2/P1 current ratio (at +10 mV) was calculated and plotted with respect to time, in either the absence (○, n = 7 for 0 and 5 min, n = 5 for 10 and 15 min, n = 3 for 20 min) and presence of 100 μm (▴, n = 7 for 0 and 5 min, n = 6 for 10 min), 120 μm (▾), n = 6 for 0, 5, and 10 min, n = 4 for 15 min), and 200 μm (•), n = 5 for 0 min, n = 4 for 5 min, n = 3 for 10 min) GTPγS; and in the presence of 120 μm GDPβS (▵), n = 5 for 0 and 6 min, n = 4 for 12 min, n = 3 for 18 min). Significantly different from the 0 μm GTPγS group, *P < 0.01; +P < 0.05, nonpaired t  test. (E ) P1 current magnitude measured at 7 min from forming whole cell recording; n values are indicated. Significantly different from the 0 μm GTPγS group, **P < 0.00; +P < 0.05. Left Y-axis shows absolute current values and right Y-axis shows current values normalized to the mean value of the 0 μm GTPγS group.