Figure 5. Ca_V2.2 α₁ OE Results in Slight Loss of Ca_V2.1 Currents, while Ca_V2.1 α₁ OE Results in an Increase in Ca_V2.1 Currents at P20/21 Calyx.

(A) Experimental timeline from virus injection into CN at P14 to electrophysiological recordings at P20/21.

(B) Confocal images of brainstem slices injected with Ca_V2.1 α₁ OE construct. (Left) CN injection site. (Right) Contralateral MNTB with mEGFP-expressing calyx of Held terminals.

(C) Pharmacological isolation of Ca_V2 isoforms expressed in the presynaptic terminal at P21 in control (n = 3) and Ca_V2.2 α₁ OE (n = 3). Average current traces before application of blockers (black), after applying 200 nM ω-agatoxin IVA to specifically block Ca_V2.1 (Aga, brown) and after applying 2 μM ω-conotoxin GVIA to specifically block Ca_V2.2 (Cono, blue).

(D) Ca²⁺ current amplitudes before blocker application (black, n.s., two-tailed t test), Aga-sensitive Ca²⁺ current amplitudes (brown, n.s., one-tailed t test), and Cono-sensitive Ca²⁺ current amplitudes (blue, 0.016, one-tailed t test).

(E) Relative Ca²⁺ current fractions sensitive to blockers.

(F) Average Ca²⁺-current traces to 10 ms step depolarizations from −80 mV holding to voltages between −50 and +40 mV for control (left, n = 9) and Ca_V2.1 α₁ OE (right, n = 10).

(G and H) Current-voltage relationships of either peak Ca²⁺ currents (G) or tail Ca²⁺ currents (H). All data are shown as mean ± SEM. See also Table S4.