Which of the following manipulations would reduce the release of neurotransmitter from a presynaptic neuron terminal?
A) addition of tetrodotoxin to the extracellular fluid at the axon terminal
B) increase in extracellular sodium and potassium ion concentrations at the axon terminal
C) reduction in extracellular calcium ion concentration at the axon terminal
D) All of the above manipulations would reduce the release of neurotransmitter.

Question

Quizplus · Accepted Answer

Calcium ions are necessary for the fusion of synaptic vesicles containing neurotransmitter with the presynaptic membrane and subsequent release of neurotransmitter into the synaptic cleft. Therefore, reducing extracellular calcium ion concentration would reduce the release of neurotransmitter. Tetrodotoxin blocks voltage-gated sodium channels, preventing the action potential necessary for the release of neurotransmitter, and increasing extracellular sodium and potassium ion concentrations would have no direct effect on the release of neurotransmitter.

Which of the Following Manipulations Would Reduce the Release of Neurotransmitter