Figure 4.

μ Opioid-mediated regulation of voltage-dependent calcium channels in DRG neurons. (A) Whole-cell calcium currents were evoked by 100-msec steps to +10 mV from V_h = −80 mV just before and after the addition of 100 nM and 300 nM DAMGO (●). Calibration bars: 1 nA, vertical; 20 msec, horizontal. (B) Concentration–response relationship of DAMGO-mediated inhibition of Ca²⁺ current in wild-type (+/+) and PLC β3-null (−/−) DRG neurons, plotted as percent reduction in peak whole-cell current magnitude. The data from responding cells are presented as mean ± SEM. The ratios within each column represent the proportion of neurons in which the DAMGO-mediated reduction of peak whole-cell current was ≥10% of the control current out of the total number of cells tested. Data were compared by using Student’s two-tailed t test (∗, P ≤ 0.02).