Effect of Siah1a expression on mGluR-mediated calcium current modulation. A and C, Sample current traces illustrating calcium current before and during inhibition by 100 μM glutamate in cells expressing mGluR5b (A) and mGluR5b + Siah1a (C). A triple pulse voltage protocol was used wherein cells were sustained at a holding potential of-80 mV and stepped to an initial test pulse to +10 mV for 25 msec, to +80 mV for 50 msec, then following a 10 msec step to -80 mV a second test pulse to +10 mV was applied. The scale bars indicate 20 msec and 0.4 nA. Tail currents were cropped to better illustrate the step currents. B and D, Time course of inhibition by glutamate (Glu) and norepinephrine (NE) in the cells illustrated in A and C, respectively. Closed circles represent measurements taken from the prepulse (the first test pulse to +10 mV). Open circles represent measurements taken from the postpulse (the second test pulse to +10 mV).