HPDL1: Nature's favourite Target: Toxins Targetting Cholinergic Transmission Flashcards
Why do plants have toxins?
to protect against predation (as they can’t move away from predators)
What’s the toxin in tobacco?
Nicotine
what sort of chemical is nicotine?
an alkyloid
what’s an alkyloid?
a nitrogen-containing compound in plants
if an animal has low tolerance to nicotine what happens when ingested/absorbed?
illness
what can nicotine be used for?
an insecticide (prevents predation by insects)
what does nicotine do physiologically?
acts as an agonist at nicotinic receptors- involved in autonomic ganglion, causing an increase in Heart rate, issues with the GI tract etc.
what’s the active toxin in Laburnum?
Cytisine
what’s the structure of Cytisine?
bridged ring structure (aromatic)
what do the seed pods of Laburnum look like?
pea pods
what does cytisine do physiologically?
a potent agonist at ganglionic nAChR and CNS subtypes
causes- Tachycardia, diarrhea, coma, convulsions- can be fatal
what do curare alkyloids do physiologically?
it’s a potent antagonist at muscle nAChR and acts at ganglionic receptors
causes- flaccid paralysis and if left untreated- respiratory paralysis that can be fatal
what are curare alkyloids used for?
- in some tribes as hunting darts
- used to be used in surgery- has now been replaced by less damaging drugs
is it safe to eat animals shot by curare alkyloid darts? and why?
yes- because it contains charged N+s so can’t easily cross cell membranes (lipophobic)
what are tropane alkyloids found in?
Datura stramonium (Jimson weed) Atropa belladonna (deadly nightshade)
what substances do tropane alkyloids contain? (2)?
atropine and hyoscine etc.
what can hyoscine be used for?
motion sickness, depression, ‘truth drug’
What do cholinesterase inhibitors target?
termination of signalling
give 2 examples of plants where cholinesterase inhibitors are found
Chinese furmoss, Daffodils, Snowdrops, Calabar bean
Name the 3 important cholinesterase inhibitors
Physostigmine
Huperzine A
Galantamine
What could all 3 cholinesterase inhibitors treat?
Alzheimers
Why do animals have toxins? (4)
- hunting of prey
- pre-digestion
- protect against predation
- paralysis of prey (makes them easier to catch and eat)
what does alpha- cobratoxin do?
very potent antagonist at neuromuscular junction nAChR
It binds so tightly it’s basically an irreversible antagonist
Blocks neuromuscular transmission, therefore causes flaccid paralysis or prey and death by asphyxiation
How do cobras and mongoose protect themselves from alpha- cobratoxin?
Has glycosylation over the nAChR which blocks the alpha-cobratoxin, however not large enoug hto block acetylcholine- so still functional
