HPDL1: Nature's favourite Target: Toxins Targetting Cholinergic Transmission

Question 1

Why do plants have toxins?

Answer 1

to protect against predation (as they can’t move away from predators)

Question 2

What’s the toxin in tobacco?

Answer 2

Nicotine

Question 3

what sort of chemical is nicotine?

Answer 3

an alkyloid

Question 4

what’s an alkyloid?

Answer 4

a nitrogen-containing compound in plants

Question 5

if an animal has low tolerance to nicotine what happens when ingested/absorbed?

Answer 5

illness

Question 6

what can nicotine be used for?

Answer 6

an insecticide (prevents predation by insects)

Question 7

what does nicotine do physiologically?

Answer 7

acts as an agonist at nicotinic receptors- involved in autonomic ganglion, causing an increase in Heart rate, issues with the GI tract etc.

Question 8

what’s the active toxin in Laburnum?

Answer 8

Cytisine

Question 9

what’s the structure of Cytisine?

Answer 9

bridged ring structure (aromatic)

Question 10

what do the seed pods of Laburnum look like?

Answer 10

pea pods

Question 11

what does cytisine do physiologically?

Answer 11

a potent agonist at ganglionic nAChR and CNS subtypes

causes- Tachycardia, diarrhea, coma, convulsions- can be fatal

Question 12

what do curare alkyloids do physiologically?

Answer 12

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

Question 13

what are curare alkyloids used for?

Answer 13

• in some tribes as hunting darts

- used to be used in surgery- has now been replaced by less damaging drugs

Question 14

is it safe to eat animals shot by curare alkyloid darts? and why?

Answer 14

yes- because it contains charged N+s so can’t easily cross cell membranes (lipophobic)

Question 15

what are tropane alkyloids found in?

Answer 15

Datura stramonium (Jimson weed)
Atropa belladonna (deadly nightshade)

Question 16

what substances do tropane alkyloids contain? (2)?

Answer 16

atropine and hyoscine etc.

Question 17

what can hyoscine be used for?

Answer 17

motion sickness, depression, ‘truth drug’

Question 18

What do cholinesterase inhibitors target?

Answer 18

termination of signalling

Question 19

give 2 examples of plants where cholinesterase inhibitors are found

Answer 19

Chinese furmoss, Daffodils, Snowdrops, Calabar bean

Question 20

Name the 3 important cholinesterase inhibitors

Answer 20

Physostigmine
Huperzine A
Galantamine

Question 21

What could all 3 cholinesterase inhibitors treat?

Answer 21

Alzheimers

Question 22

Why do animals have toxins? (4)

Answer 22

• hunting of prey
• pre-digestion
• protect against predation
• paralysis of prey (makes them easier to catch and eat)

Question 23

what does alpha- cobratoxin do?

Answer 23

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

Question 24

How do cobras and mongoose protect themselves from alpha- cobratoxin?

Answer 24

Has glycosylation over the nAChR which blocks the alpha-cobratoxin, however not large enoug hto block acetylcholine- so still functional

Question 25

What are mamba toxins also known as?

Answer 25

dendrotoxins

Question 26

What do mamba toxins target? (2)

Answer 26

• K+ channels

- mAChR

Question 27

What type of toxin is Botulinum toxin?

Answer 27

peptide

Question 28

What actually is the botulinum toxin?

Answer 28

an enzyme

Question 29

How does the Botulinum toxin work?

Answer 29

prevents the release of ACh at the NMJ
Does this by cleaving the SNARE proteins, therefore preventing vesicle fusion to the pre-synaptic membrane- therefore ACh won’t be released
results in fatal paralysis

Question 30

How do cone snails hunt their prey?

Answer 30

harpoon them with a harpoon containing toxins

Question 31

How many Conotoxins are there?

Answer 31

1000s

Question 32

What are Conotoxins named after?

Answer 32

species and their target

Question 33

What do conotoxins target?

Answer 33

nAChR (block)

Question 34

what do omega conotoxins

target?

Answer 34

Calcium channels (block)

Question 35

What’s the structure of conotoxins?

Answer 35

small peptides with cysteine bridges- are compact

Question 36

What are the therapeutic applications of conotoxins?

Answer 36

chronic pain (many more uses still to be discovered)

Question 37

What do Phantasmal frogs have in their skin/ skin secretions?

Answer 37

alkyloids

Question 38

What specifically is the name of the alkyloid in the skin/secretions of the phantasmal frog?

Answer 38

epibatidine

Question 39

what does epibatidine do?

Answer 39

v. potent agonist at neuronal nAChRs