Fig. 3.

Electrical stimulation (5 Hz) and K⁺ depolarization induce TH expression by activating distinct calcium channel subtypes. Each bar represents the percentage of total neurons in stimulated and unstimulated (Ctrl) cultures exhibiting TH immunoreactivity in the absence or presence of 2 μm nimodipine, an L-type calcium channel antagonist, or 1 μm ω-conotoxin, an N-type calcium channel antagonist. Data are presented as the mean ± SEM. Comparisons among groups were made using ANOVA followed by Duncan's multiple range test; ***p ≤ 0.001.