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Neurotoxins

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Neurotoxins
Content:-
What is Neurotoxins
Introduction of neurons
Mechanism action of neurotoxins
Different neurotoxins and its mode of action
Reference


The point where your muscles and nervous system meet is called the neuromuscular junction (NMJ)


ACh Receptor Channel Opens


Scorpions, spiders

Contain low molecular weight proteins that affect ion transport along axon
Impairs action potential
Symptoms include tachycardia, respiratory distress

PESTICIDES
Malathion , parathion, “nerve gases” like organophosphorous pesticides and DDT like organochlorine like pesticides Inhibits acetyl cholinesterase (AChE) leading to continuous stimulation.
Fasciculin inhibits mammalian and fish acetylcholinesterases
Neurobehavioral, cognitive, neuromuscular disturbances
Death from respiratory distress
Acetycholin-esterase
AChE hydrolyzes Ach into choline & acetate .
Puffer fish





Botulinum toxin cleaves SNARE proteins. SNARE proteins are involved with fusing synaptic vesicles to the plasma membrane. Cleaving of SNARE proteins by botulinum toxin therefore inhibits the release of acetylcholine at the neuromuscular junction, and leads to inhibition of neurotransmission.

This means acetylcholine isn’t released at the neuromuscular junction, so muscles are paralysed.




Both cause poisoning by interfering with they way muscle contractions are regulated.

Muscles become very sensitive to stimulation and instead contracting and then releasing, they go into spasm


Reference
Toxipedia
Neuroscience online: An electronic textbook of neuroscience





Neurotoxins

  1. 1. 1
  2. 2.  What is Neurotoxins  Introduction of neurons  Mechanism action of neurotoxins  Different neurotoxins and its mode of action  Reference 2
  3. 3. 3
  4. 4. 4
  5. 5. 5
  6. 6. Signals sent from your central nervous system to the NMJ tell muscles to move The synapses at the NMJ use a neurotransmitter called acetylcholine 6
  7. 7. many poisons are neurotoxins Most of them work by interfering with control of muscle contractions They cause death because they stop the heart and lungs from working 7
  8. 8. different neurotoxinswork in different ways… Neurotoxins that work like this are found in: some snake and spider venom; poison arrow frogs; many scorpion stings Many neurotoxins cause difficulty to fire the electrical signal(action potential). 8
  9. 9. Cobra toxin blocks acetylcholine receptors Left untreated, a bite from an Indian Cobra can kill in just 1 hour Acetylcholine can’t bind to its receptors, so the signals that control your muscles are blocked and your muscles, including your heart and diaphragm, are paralysed Some interfere with the action of acetylcholine at the NMJ 9
  10. 10. 10
  11. 11. 11
  12. 12.  Contain low molecular weight proteins that affect ion transport along axon › Impairs action potential  Symptoms include tachycardia, respiratory distress 12
  13. 13.  Malathion , parathion, “nerve gases” like organophosphorous pesticides and DDT like organochlorine like pesticides Inhibits acetyl cholinesterase (AChE) leading to continuous stimulation.  Fasciculin inhibits mammalian and fish acetylcholinesterases  Neurobehavioral, cognitive, neuromuscular disturbances  Death from respiratory distress 13
  14. 14. AChE hydrolyzes Ach into choline & acetate . 14
  15. 15. • The active toxin in the tissues of this fish is a chemical called tetrodotoxin. • Tetrodotoxin is a neurotoxin - it affects nerve cells (neurons). • Specifically, tetrodotoxin blocks voltage-gated sodium ion channels. 15
  16. 16. 16
  17. 17. Puffer fish for sale at Kuromon Ichiba market, Osaka, Japan Puffer fish (or fugu) is a potentially lethal Japanese treat One puffer fish contains enough neurotoxin to kill 30 people Fugu can only be prepared by specially trained chefs who carefully remove all the parts of the fish that contain the poison There is no known antidote 17
  18. 18. Botulinum toxin (Botox) is a neurotoxin produced by bacteria called Clostridium Botulinum. It is the most powerful and naturally occurring neurotoxin yet discovered and causes poisoning that can be fatal (botulism) It is used medically to treat muscle spasms and cosmetically to reduce wrinkles. It works by preventing vesicles containing neurotransmitter from fusing with the pre synaptic membrane. 18
  19. 19.  Botulinum toxin cleaves SNARE proteins. SNARE proteins are involved with fusing synaptic vesicles to the plasma membrane. Cleaving of SNARE proteins by botulinum toxin therefore inhibits the release of acetylcholine at the neuromuscular junction, and leads to inhibition of neurotransmission.  This means acetylcholine isn’t released at the neuromuscular junction, so muscles are paralysed. 19
  20. 20. Strychnine is a highly toxic, colourless, bitter crystalline alkaloid used as a pesticide to control rats, moles, gophers, and coyotes. Strychnine is highly toxic to most domestic animals. Its oral LD50 in dogs, cattle, horses, and pigs is 0.5–1 mg/kg, and in cats is 2 mg/kg. Strychnine was used by the winner of the 1904 Olympic marathon to improve performance It is still banned in sport, but its use rarely detected. 20
  21. 21. Tetanus is caused by the neurotoxin tetanospasmin which comes from a bacterium called Clostridium tetani are found in soil, dust and animal feces. When they enter a deep flesh wound, spores of the bacteria may produce a powerful toxin, tetanospasmin, which actively impairs your motor neurons, nerves that control your muscles. 21
  22. 22.  Both cause poisoning by interfering with they way muscle contractions are regulated.  Muscles become very sensitive to stimulation and instead contracting and then releasing, they go into spasm 22
  23. 23. 23
  24. 24. Curare is used by some indigenous South American tribes for poison darts It comes from the curare plant Its a antagonist of nicotinic acetylcholine receptors Curare paralyses muscles by blocking acetylcholine receptors At the right dose, it has medical uses. It was one of the first chemicals used as a muscle relaxant in anaesthesia 24
  25. 25.  Toxipedia  Neuroscience online: An electronic textbook of neuroscience  www.google.com (images) 25
  26. 26. 26

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