Fig. 2: UNC80 is required for the TTX-resistant Na⁺ leak current and its regulation by extracellular Ca²⁺.

a, b Representative TTX-resistant Na⁺ leak current recorded in hippocampal neurons cultured from WT (+/+) (a) and UNC80 KO (−/−) (b) pups. Each trace represents 1 s of currents recorded at −70 mV in bath solutions with varying [Na⁺] (140 or 14 mM) and [Ca²⁺] (2 or 0.1 mM). The Na⁺-leak current (ΔI_LNa) is calculated as the difference of current sizes between those recorded under 140 mM [Na⁺] and 14 mM [Na⁺], as indicated by dashed lines. c–e Similar to a, but recorded from UNC80 KO neurons transfected with UNC80 (c), NALCN (d), or UNC79 (e) cDNA. f Averaged sizes of currents in a–e. I_LCa is the current activated by lowering [Ca²⁺] from 2 to 0.1 mM, as defined as the size difference of ΔI_LNa under the two [Ca²⁺] conditions). Data are presented as mean values ± SEM. Numbers of neurons are in parentheses. In (f), two sample t test of each group against the “+/+” group (n = 5) was performed: “−/−” (n = 8, p ≤ 0.001), “−/−; UNC80” (n = 6, p = 0.326), “−/−; NALCN” (n = 5, p ≤ 0.001), “−/−; UNC79” (n = 7, p ≤ 0.001). Asterisk “*” indicates p < 0.05. Source data are provided as a Source Data file.