Fig. 1.

TH induction by electrical stimulation and K⁺ depolarization. Dissociate cultures of E16.5 PG neurons were stimulated at 5 Hz continuously (0.2 msec alternating polarity pulses), at 25 Hz for 2 sec once every 10 sec, or chronically with 40 mm KCl. After 6 hr of stimulation, neurons were cultured for an additional 12 hr in control conditions and then processed for TH–NF immunocytochemistry. Each barrepresents the percentage of total neurons exhibiting TH immunoreactivity. Data are presented as the mean ± SEM. Comparisons among groups were made using ANOVA followed by Duncan's multiple range test; ***p ≤ 0.001.