Draw and predict the effects of: (1) Curare from poison dart frogs is a competit

Question

Draw and predict the effects of:    (1) Curare from poison dart frogs is a competitive inhibitor of Ach; that is, it binds to Ach receptors, does not open the sodium channel, and prevents Ach from binding.    (2) Nerve gas is an acetylcholinestrase inhibitor.    (3) The toxin produced by botulism bacteria is an Ach-blocker, that is, it prevents its secretion from motor neurons.    (4) Botox (the toxin from botulism bacteria) is used to treat excessive sweating. Sweat glands are controlled by motor neurons. Explain how/why botox might be an effective treatment for excessive sweating.

Explanation / Answer

1. Curare is a nondepolarizing blockers.

the site of action of curare is the end plate of skeletal muscle.The site of action of curare is the neuromuscular
junction. curare acts peripherally and not centrally.

The competitive blockers have affinity for the
nicotinic (NM) cholinergic receptors at the muscle
end plate

Nicotinic receptors combine with the
cationic head of ACh -7 opening of Na+ channel.

Most of the competitive blockers have two or
more quaternary N+ atoms which
provide the necessary attraction to the same site,
but the bulk of the antagonist molecule does not
allow conformational changes in the subunits
needed for opening the channel. Competitive
blockers generally have thick bulky molecules
and were termed Pachycurare by Bovet (1951).
ACh released from motor nerve endings is not
able to combine with its receptors to generate end
plate potential (EPP). curare thus reduces the
frequency of channel opening but not its
duration or the conductance of a channel once
it has opened. When the magnitude of EPP falls
below a critical level, it is unable to trigger
propagated muscle action potential (MAP) and muscle fails to contact

1 . Skeletal muscles - Intravenous injection of
nondepolarizing blockers rapidly produces
muscle weakness followed by flaccid paralysis.
Small fast response muscles (fingers, extraocular)
are affected first; paralysis spreads to hands,
feet-arm, leg, neck, face-trunk-intercostal
muscles-finally diaphragm: respiration stops

3. Histamine release - cuare releases histamine
from mast cells.Histamine release contributes to
hypotension produced ; flushing, bronchospasm
and increased respiratory secretions
are other effects

4. C.V.S.- significant fall in BP

5. G.I.T. The ganglion blocking activity of
competitive blockers may enhance postoperative
paralytic ileus after abdominal operations.

2. NErve gas is an anti cholinesterase

3. the botulinum toxin mainly causes flaccid paralysis of the muscles, it reduces xcessive sweating and neuropathic pain

4.. Sympathetic cholinergic nerves activate thermoregulatory and emotional sweating. these are controlled by different CNS neuron

botox block acetylcholine release and other neurotransmitters from presynaptic vesicles by deactivating SNARE proteins.

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