Berberine does not alter the synaptosomal membrane potential but reduces the 4-AP-induced increase in cytosolic Ca²⁺ concentration ([Ca²⁺]_C).

<p>A: Synaptosomal membrane potential monitored with DiSC₃(5) in the absence (control) and in the presence of 10 µM berberine, added 10 min before depolarization with 1 mM 4-AP. Inset: Glutamate release was induced by 15 mM KCl in the absence (control) or presence of 10 µM berberine, added 10 min before depolarization. B: Cytosolic free Ca²⁺ concentration (nM) was monitored using Fura-2 in the absence (control) and in the presence of 10 µM berberine, added 10 min before depolarization with 1 mM 4-AP. Results are mean ± SEM of 5 independent experiment. ***, P<0.001,* *, P<0.01 versus control group.