Summary of neuronal Ca2+ responses. Panel A depicts summary data from 7 coverslips for each genotype, showing the mean amplitude of spontaneous Ca2+ oscillations were not different between Snap25+/+ (+/+) and Snap25+/- (+/-) cultures. Panel B, amplitude of Ca2+ elevations evoked by K+-depolarization in Snap25+/+ (+/+), Snap25+/- (+/-) and Snap25-/- (-/-) cultures (n = 7,6,8, respectively). TTX (1 μM) was present throughout K+ challenges. Panel C shows effects of sequential bath application of Ca2+ channel blockers in 55 mM KCl containing media to assess the role of voltage-gated calcium channels in depolarization triggered Ca2+ elevations of pooled results from Snap25+/- and Snap25+/+ (+/- and +/+) compared to Snap25-/- (-/-) neurons. Responses were normalized to 55 mM K+ challenges in control buffer. Con, control (TTX only), Nim, nimodipine (10 μM), conotoxins GVIA and MVIIC (1 μM).