Fig. 4. Association of L-type Ca²⁺ and BK channels. (A) Western immunoblots of proteins isolated from soluble whole brain extracts by immunoprecipitation using anti-BK_1118-1135 (BK-IP). Probing BK-IP and rabbit IgG co-IPs (IgG-IP) samples with anti-Ca_V1.2 revealed a weak band of 210 kDa in the BK-IP sample lane, with a weaker reactivity observed in the IgG control co-IP lane. Enrichment of the immunoreactive band for Ca_V1.2 in the BK-IP sample demonstrated the specificity of the immunoprecipitation (n=3). (B,C) Cell-attached patch records from two separate cells co-transfected with rSlo₂₇ and Ca_V1.2/Ca_V3 subunits. The vast majority of outward channel openings (derived from rSlo₂₇) were not associated with any inward channel opening (derived from Ca_V1.2/Ca_V3). In very rare examples, a near coincident opening of rSlo₂₇ channels with inward opening of Ca_V1.2/Ca_V3Ca²⁺ channels was observed. The close temporal association of these two expressed channels is seen in the expanded trace. The full amplitude of the rSlo₂₇ openings has been truncated to resolve the small amplitude inward channel openings.