Lecture 24 - Neuromuscular Junction Toxins

Question 1

Agatoxin from funnel web spiders alters the voltage P/Q _____ channels require to open –> no influx into axon terminal –> no vesicle release of NTs. Remember that _____-_____ syndrome acts in a similar way, but these patients produce autoAbs to these channels. Which class of antibiotics have a similar effect?

Answer 1

Ca++ channel

Lambert-Eaton

Aminoglycosides

Question 2

______ is used in high doses to treat preeclampsia. It acts the same way aminoglycosides act. How is that?

Answer 2

Mg++

It blocks P-type Ca++ channels

Question 3

Phospholipase A2 is a Beta-neurotoxin that inhibits ______, so synaptobrevin can’t bind, and vesicle fusion is blocked. The patients will characteristically exhibit ______ (symmetric or asymmetric?) descending weakness in a proximal to distal pattern. This is significant bc stroke syndromes don’t present this way.

Answer 3

Syntaxin

Symmetric

Question 4

Alpha-Latrotoxin is produced by ____ _____ spiders. It _____ (increases or decreases?) Ca++ influx. Stonustoxin is very similar and is produced by _____.

Answer 4

Black Widow spiders

Increases Ca++

Stonefish

Question 5

Persistent ______ agonists cause paralysis by overstimulating their receptors, which keeps a depolarized voltage constant –> this does not allow the voltage gated Na+ channels to close. What is an example of such an agonist that is resistant to AChE?

Answer 5

Nicotinic

Succinylcholine

Question 6

Mamba snakes produce Fasciculin toxins that act as _______ inhibitors. They irreversibly bind and inactivate the enzyme outside of its active site.

Answer 6

AChE inhibitors

Question 7

______ is a nicotinic antagonist. Interestingly, the plant that produces it also produces Strychnine that act the same way, but causes motor movement. This is the same relationship that Botox has with Tetanus (remember Botox at NMJ and Tetanus at spinal interneuron.)

Answer 7

Curare

Question 8

Which Na+ channels do Tetrodotoxin act on?

Answer 8

Na+ in the nodes of Ranvier on axons.

Question 9

Soluble ______ causes severe hypokalemia.

Answer 9

Barium