Action Potentials and Synaptic Transmission (3A) Practice Test

In a neuromuscular junction preparation, a toxin was applied that cleaves a SNARE protein required for synaptic vesicle fusion. End-plate potentials (EPPs) were recorded in the muscle fiber in response to motor neuron stimulation. The concept being tested is vesicle fusion as a prerequisite for neurotransmitter release. Which observation best explains the expected change in EPPs?

In an experiment on myelinated peripheral axons, a compound was applied that selectively blocks voltage-gated Na+ channels at nodes of Ranvier but does not affect internodal membrane properties. The concept being tested is saltatory conduction and the requirement for nodal Na+ currents. Which outcome is most consistent with this manipulation?