Modulation of M-current by CHPG in SCG neurons expressing either mGluR5b or mGluR1a. A, Left, Average (±SEM) calcium current by 1 mM CHPG (open) and 100 μM Glu (filled), in SCG neurons expressing mGluR5b or mGluR1a, as indicated. Number of cells in each group is shown in parentheses. Right, Average (±SEM) ratio of CHPG/Glu inhibition of calcium current in the same cells as in Left. Asterisk indicates p < 0.05, T-test. Note that since ratios are non-linearly distributed around unity, statistical tests were performed on the natural log of the ratio (CHPG/Glu inhibition) from each individual cell. B, Sample current traces illustrating M-current inhibition in an mGluR1a expressing cell. In this cell, CHPG had little effect while Glu strongly inhibited the current. M-currents were measured as the tail current deactivating during a hyperpolarizing step to −60 mV from a holding potential of −30 mV (to inactivate other K+ channels). Voltage protocol is shown below. C, Distribution of percent inhibition by CHPG plotted against the inhibition by Glu in each cell.