How Were Extracellular Ion Concentrations Manipulated in the Experiments Supporting

Multiple Choice

How were extracellular ion concentrations manipulated in the experiments supporting the theory of quantal release of neurotransmitters?

A) Ca²⁺ was increased in the extracellular fluid so that action potentials would release many vesicles.
B) Ca²⁺ was absent in the extracellular fluid so that action potentials would release no vesicles.
C) Mg²⁺ replaced Ca²⁺ in the extracellular fluid so that action potentials would release few vesicles.
D) Mg²⁺ replaced Ca²⁺ in the extracellular fluid so that action potentials would release many vesicles.