Question

A pharmacy student is testing six different drugs that target neuromuscular transmission. Predict if the following drugs would increase, decrease or not change the magnitude of the end plate potential at the neuromuscular junction.

Acetylcholinesterase inhibitor

      [ Choose ]            No change            Increase            Decrease      

Botulism toxin

      [ Choose ]            No change            Increase            Decrease      

Black widow latrotoxin

      [ Choose ]            No change            Increase            Decrease      

Antagonist of presynaptic voltage-gated Ca2+ channels

      [ Choose ]            No change            Increase            Decrease      

Antagonist of Ach receptors

      [ Choose ]            No change            Increase            Decrease      

Antagonist of sarcolemmal voltage-gated Na+ channels

[ Choose ]            No change            Increase            Decrease

Answer 1

1.Acetylcholinesterase Inhibitors-Increase Endplate potentials.

Acetyl choline inhibitors are the drugs that inhibit Acetylcholinesterase,which degrade Acetylcholine.So it increases concentration of Acetyl choline which increases levels of Acetyl choline binding to post synaptic membrane which increase Endplate potential.

2.Botulism Toxin-Decrease Endplate potentials

Botulsim toxin binds to presynaptic Axon terminals and prevent the release of Acetylholine from presynapticc membrane which causes decrease in neurotransmitter binding Post synaptic membrane--Decrease Endplate potential

3. Black widow latrotoxin -Increase

Black widow Latrotoxin (α-Latrotoxin) is a presynaptic neurotoxin which is isolated from venom of black widow spider .It causes excessive release of Neurotransmitter Which increase Endplate potential very high ,Finally leading to painful skeletal muscle spasms & rigidity

4. Antagonist of presynaptic voltage-gated Ca2+ channels -Decrease.

Presynaptic voltage gated ca2+ channel release of calcium is necessary for Synaptic vesicle fusion with presynaptic membrane & release of Neurtorasmitter.So Antagonist of presynaptic voltage-gated Ca2+ channels -Decrease endplate potential

5. Antagonist of Ach receptors -Decrease.

Acetyl choline binds to Ach receptors in post synaptic membrane of motor endplate which enables entry of Positive ions responsible for initiation of depolarasartion,So Antagonist of Ach receptors -Decrease Endplate potential

6. Antagonist of sarcolemmal voltage-gated Na+ channels -No change

Endplate potential remains normal,The propogation of Action potential is reduced