L4 - Neurotoxins and Venoms Flashcards
Where does Ouabain target and what effects does it have?
Target: Na+/K+ ATPase
Time: 3-10minutes intravenously to act
Ouabain is a cardiac glycoside - low does can be used to treat hypotension and some arrhythmias, but high doses are toxic
It works by inhibiting the Na/K ATPase, causing Na+ concentration to increase inside the cell. This stops the NCX from working causing intracellular calcium levels to increase.
This causes cardiac contractibility and vagal tone to be higher, which can cause a MI
Where does Tetrodoxin (TTX) target?
Target: VG Na+ channels
Where is Tetrodoxin (TTX) found in nature?
Pufferfish and other animals - but is actually produced by symbiotic bacteria in these animals.
Causes the ‘red tide’
What effects does Tetrodoxin (TTX) have on humans?
It binds to VG NA+ channels disabling them. This stops the body being able the send signals to the brain.
Causes a loss of sensation and paralysis of voluntary muscles - including the diaphragm and intercostal muscles = stops breathing
What toxin is found in Funnel Web Spiders and where in the body does it target?
Atracotoxin - causes inactivation of Na+ channels
What does (TEA) stand for?
Tetraethylammonium (TEA)
What target and effect does (TEA) have?
Target: VG K+ channels
It is nicknames a ‘ganglion blocker’
Apamine is a small neurotoxin found in bees, what is it and what does it do?:
It is a small neurotoxin that can pass the blood-brain barrier.
It inhibits calcium activated K+ channels in neurons which are responsible for the after hyperpolarisation in neurones.
Where is Dendrotoxin found?
Black Mamba snake
The bite of a black mamba can potentially cause collapse in humans within 45 minutes, or less. Without effective antivenom therapy, death typically occurs in 7-15 hours
What effects does Dendrotoxin have?
Blocks K+ channels therefore K+ cannot escape during an action potential
- prolonged duration of APs
- increased ACh release at neuromuscular junction
- hyperexcitability and convulsions
What kin of snail produces a toxin that effects VG Ca2+ channels and what effect does this have?
Cone Snails
Cone snails use a radula tooth as a harpoon-like structure for predation. Each of these harpoons is a modified tooth, primarily made of chitin and formed inside the mouth of the snail, in a structure known as the toxoglossan
radula. It contains conotoxins:
α conotoxins - nACh receptor
µ conotoxins - muscle VG Na+ channels
Ω conotoxins - VG Ca2+ channels
What venom does the Black Widow spider release and where does it target?
Toxin: Latrotoxin
Latrodectism is the illness caused by the bite of Latrodectus spiders (the black widow spider and related species).
Pain, muscle rigidity, vomiting, and sweating are the hallmarks of latrodectism. Contrary to popular conception, latrodectism is very rarely fatal to people
What does Botulinum do?
Botulinum toxin (BTX) is a neurotoxic protein produced by the bacterium Clostridium Botulinum and related species.
Botulinum blocks exocytosis - It prevents the release of the acetylcholine the neuromuscular junction and thus causes flaccid paralysis.
Infection with the bacterium causes the disease botulism. The toxin is also used commercially in medicine, cosmetics, and research.
Botulinum is the most acutely lethal toxin known, with an estimated human median lethal dose (LD50) of 1.3–2.1 ng/kg intravenously or intramuscularly and 10–13 ng/kg when inhaled.
What is Curare and what has it be used historically?
A bitter resinous substance obtained from the bark and stems of some South American plants.
It paralyses the motor nerves and is traditionally used by some Indian peoples to poison their arrows and blowpipe darts.
What effect does Curare have?
Curare is an example of a non-depolarizing muscle relaxant that blocks the nicotinic acetylcholine receptor (nAChR), one of the two types of acetylcholine (ACh) receptors, at the neuromuscular junction.
It causes anaesthesia
