A, Cartoon depicting CaV2.1 α1 subunit distal C-terminal interaction partners. B, left: Schematic view of stereotactic surgery to inject/coinject HdAd vectors expressing Cre + eGFP and CaV2.1 constructs + mCherry into the aVCN at age P1. Right: top: Experimental timeline from virus injection at P1 to electrophysiological recordings at P9-P11 prior to the onset of hearing (P12). Middle and bottom: schematic view of the viral constructs used, expressing either Cre + eGFP or CaV2.1 constructs + mCherry, respectively, driven by individual promotors. C, Calyx of Held terminals transduced with Cre + eGFP (top) and CaV2.1 + mCherry (middle). eGFP and mCherry signals overlap with those of a calyx of Held loaded with Lucifer Yellow via a patch pipette (bottom).