Figure 1.

Heterologously expressed hSNSR4 couples to HVA but not LVA Ca²⁺ channels in rat DRG neurons. A, Representative whole-cell patch-clamp I_Ca traces acquired in the absence or presence of the peptide agonist BAM8-22 (BAM; 3 μm) from a control (Con; top) or an EGFP-expressing DRG neuron (middle). The voltage protocol used to evoke I_Ca for experiments described in Fig. 1 is illustrated at the bottom. The current evoked at -40 mV arises from LVA Ca²⁺ channels, whereas the current evoked at +10 mV (after an inactivating interpulse) arises primarily for HVA Ca²⁺ channels. B, Representative current traces (top) illustrating marked inhibition of I_Ca evoked (+10 mV) after application of BAM8-22 to a DRG neuron expressing hSNSR4. The neuron illustrated exhibited virtually no LVA Ca²⁺ channels. The time course of inhibition is shown at the bottom. C, Representative current traces (top) obtained in the absence or presence of BAM8-22 from an hSNSR4-expressing DRG neuron with a large component of LVA-type Ca²⁺ channels. The time course of inhibition is shown at the bottom. D, Summary bar graph comparing mean BAM8-22-induced inhibition of HVA (filled) and LVA (open) I_Ca under experimental conditions listed below each bar. HVA I_Ca amplitude was measured 10 msec from the start of the voltage step to +10 mV, whereas LVA I_Ca amplitude was measured 15 msec after initiation of the voltage step to -40 mV. Heterologous expression was accomplished using recombinant adenovirus.