Neurotoxins and Venoms

Question 1

Target: sodium/potassium pump

Answer 1

Ouabain
Blocks ATPase site, can no longer pump ions across cell membrane

Vertebrates: interferes with pump that exports calcium ions -elevates intracellular calcium -higher cardiac contractility.

Question 2

Target: voltage gated sodium channels

Answer 2

TTX (Tetrodotoxin)

Blocks voltage gated sodium channels -inhibits spikes.

Question 3

Where was the first source of TTX?

Answer 3

Vibrio bacteria wishing pufferfish made the substance.

Question 4

Target: voltage gated potassium channels

Answer 4

TEA (tetraethylammonium)

Corks channel -enhances release of acetylcholine at neuromuscular junction.

Question 5

Sources of TEA?

Answer 5

Apamine from bees

Dendrotoxin from mambas

Question 6

Target: Sodium channel inactivation -is normal to inactivate after a point.

Answer 6

Atracotoxin
Stops calcium channel inactivation
Remain open and axon becomes over excitable

Question 7

Where is atracotoxin found?

Answer 7

Found in venom of funnel web spider from Sydney

Toxic to apes

Question 8

Target: Voltage gated Ca++ channels

Answer 8

Cone shell toxins block the action of calcium ions in presynaptic terminal

Question 9

How many species of cone snails?

Answer 9

500

Question 10

What is the structure of conotoxins?

Answer 10

15-30 amino acid polypeptides

Question 11

Omega-conotoxins?

Answer 11

target voltage calcium channels -stop ability of neutrons to communicate with each other

Question 12

Target: Neurotransmitter release

Answer 12

Botulinum

Blocks exocytosis of vesicles

Question 13

Venom from black widow spider:

Answer 13

uncontrolled exocytosis of vesicles.

Question 14

What is an antagonist? (in terms)

Answer 14

A chemical that interferes with a normal transmitter

Question 15

Target: neurotransmitter receptors

Answer 15

Alkaloid curare: block nACH receptors (muscle relaxant)

Alpha conotoxins and components of snake venom (alpha bungatotoxin) -block nACH receptors.
Cause immobilisation -can’t communicate with muscular cells

Strychnine: toxic alkaloid -blocks glycine receptors -inhibitory synapse. Results in excitatory state -spastic muscle contractions

Question 16

How many toxic species of snake?

Answer 16

300

Question 17

What does alpha bungarotoxin do?

Answer 17

Sticks to nACH receptors -immobilisation

Question 18

What do spider toxins mainly block?

Answer 18

Glutamate receptors.

Glutamate is important for neural communication -spider venom blocks these glutamate receptors.

Question 19

Target: Neurotransmitter inactivation

Answer 19

Eserine
From plant calabar
Interferes with acetylcholinesterase
The muscle is excited for a longer period
potentiator