Figure 1.

Effects of treatments with NEU (1.5 U/ml for 1–3 h) on current-voltage (I-V) relationships in HEK293 cells expressing stable Ca_V3.2 channels grown in hyperglycemic cell culture medium. (A) Traces represent families of Ca_V3.2 T-currents evoked in representative HEK293 cells in control (top panel) vs. treated (bottom panel) cohort by voltage steps from holding potential (V_h) of −90 mV to test potentials (V_t) from −60 to −25 mV in increments of 5 mV. Traces from two cells that were evoked at the same depolarizing test potentials are depicted in the same color. (B) Graph of I-V curves shows averages of peak currents at wide range of potentials from 7 cells in control untreated conditions (black symbols) and population of cell after treatment with NEU (gray symbols). Note that NEU treatment decreased peak currents over the range of test potentials more than 2-fold. (C) When compared to untreated control cells (black symbols) treatment of HEK293 cells with NEU (gray symbols) induced significant shift of V₅₀ in steady-state inactivation curves from −79.7 ± 2.3 mV (n = 6) to −72.0 ± 2.4 mV (n = 9, p < 0.05). Similarly NEU induced depolarizing shift of V₅₀ for steady-state activation from −45.7 ± 1.0 mV in control conditions to −37.9 ± 1.9 mV after NEU treatment (n = 7, p < 0.01). We used 2 mM Ca²⁺ as a charge carrier in these experiments.