How Does the Presence of High Concentrations of Extracellular Magnesium

Multiple Choice

How does the presence of high concentrations of extracellular magnesium or cadmium ions block transmitter release?

A) Magnesium and cadmium compete with calcium for passage through the presynaptic voltage-gated calcium channel, preventing calcium entry.
B) Magnesium and cadmium compete with sodium for passage through the presynaptic voltage-gated sodium channel.
C) Magnesium and cadmium directly block synaptic vesicle fusion with the plasma membrane.
D) Magnesium and cadmium block presynaptic action potentials.
E) Magnesium and cadmium compete with potassium for passage through the presynaptic voltage-gated potassium channel.