Inhibition of quantal transmitter release by the polycationic ligand cationized ferritin

Cationized ferritin (200 micrograms ml-1) causes a reduction in both spontaneous and evoked transmitter release at the frog neuromuscular junction. The reduction in EPP amplitude probably reflects reduced Ca2+ -influx since full recovery can be achieved by elevation of [Ca2+]o. The effect on MEPP frequency is independent of [Ca2+]o and may well reflect a direct effect on exocytosis.