Figure 4. H₂O₂ mimics hypoxic and amyloid peptide augmentation of current density, but does not induce Cd²⁺-resistant evoked exocytosis.

A, mean current density vs. voltage plots (with vertical s.e.m. bars, where visible behind symbols) obtained from seven cells exposed to 40 μM H₂O₂ for 24 h. Recordings were made in the absence (•) or presence (○) of 2 μM nifedipine. Dashed line indicates, for ease of comparison, control current density (taken from Fig. 3A). B, amperometric recording of exocytosis from a representative PC12 cell exposed to 40 μM H₂O₂ for 24 h. Secretion was evoked by exposure to a perfusate containing 50 mm K⁺ (application period commencing at the beginning of the trace), and 200 μM Cd²⁺ was applied for the period indicated by the horizontal bar. Inset shows mean ± s.e.m. exocytotic frequency in H₂O₂-treated cells before (□) and during (▪) exposure to Cd²⁺.