Fig. 3. Functional coupling of N-type Ca²⁺ channels with BK channels reconstituted in tsA-201 cells. (A) Representative macroscopic currents from a cell transfected with GFP-Ca_V2.2/Ca_V3 subunits, evoked from a holding potential of –100 mV by step depolarisations (shown are 20 mV increments) from –60 mV. Below is the normalised current-voltage relationship (n=5). (B) Single channel activity conducted by 160 mM Ca²⁺ evoked by step depolarisations to +20 mV from a holding potential of –120 mV. (Ci) Cell-attached patch records from a cell co-transfected with rSlo₂₇ and GFP-Ca_V2.2/Ca_V3 subunits showing near coincident opening of rSlo₂₇ channels with inward opening of GFP-Ca_V2.2/Ca_V3 Ca²⁺ channels. The close temporal association of these two expressed channels is seen in the expanded trace (Cii), where the full amplitude of the rSlo₂₇ openings has been truncated to resolve coincident openings. (Di) Intracellular BAPTA did not disrupt the coupling between expressed GFP-Ca_V2.2/Ca_V3 and rSlo₂₇ channels. Cell-attached patch current sweeps from a BAPTA-AM (10 µM)-treated cell displayed near coincident activation of rSlo₂₇ channels following the opening of GFP-Ca_V2.2/Ca_V3 channels. The close temporal coupling of expressed channels is seen in the expanded trace (Dii).