PHL 313 (Lab. 4)
Effect of Nm blockers on Frog Rectus
Abdomens Muscle
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Rectus Abdomens Muscle .
Voluntary muscle which receive motor somatic innervations (lack
the ganglia )
Receptor is Nm which is different from receptor in the autonomic
ganglia.
It contains Ach-esterase for destruction of Ach.
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Nm drugs
Cholinergic agonists (direct acting )
• Ach
• Carbachol
• Anticholinesterases (indirect acting )
• reversible :
Neostigmine, physostigmine, pyridostigmine
• Irreversible : (e.g Organophosphates )
(isoflurophate, echothiophate )
Neuromuscular Blockers
A. Non-depolarizing : e.g. D-tubocurarine
B. Depolarizing : e.g. suxamethonium
3
Depolarization
1- Resting potential:
• In order to maintain the cell membrane potential, cells keep a
low concentration of sodium ions and high levels of potassium
ions within the cell (intracellular).
• The sodium-potassium pump moves 3 sodium ions out and
moves 2 potassium ions in, thus in total removing one positive
charge carrier from the intracellular space.
• 2- Depolarization is a positive-going change in a cell's
membrane potential, making it more positive, or less negative.
In neurons and some other cells, a large enough
depolarization may result in an action potential.
• 3- Hyperpolarization is the opposite of depolarization, and
inhibits the rise of an action potential.
4
SUCCINYLCHOLINE
SUCCINYLCHOLINE is a muscle relaxant. It relaxes muscles during
surgery or before investigational procedures.
• Succinylcholine is double Ach
• Unlike Ach, it is not hydrolysed by Achesterase.
• It is degraded more slowly than Ach causing an endplate
depolariztaion which lead to Action potential.
• It is a persist depolarization of endplate because Na
channel remain inactivated leading to relaxation of
muscle fiber (paralysis).
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Requirements
•Frog-ringer solution
-No Mg+2
(no relaxation)
-(Ca ,K ,PO4, Na ,HCO3 )
-Glucose
-Tension 0.5-4 gm
-Temp. 25 C
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Procedure
1- Add 0.2ml of Ach ,record ,wash .
2- Add 0.2ml of prostagmine , wait 2 min. ,add 0.2ml Ach , record
,wash. (compare between the response in step 1 and 2)
3- Add 0.2ml carbacol ,record ,wash .(compare between the
response in step 1 and 3)
4- Add 0,2ml succinylcholine ,record , No wash , add 0.2ml of Ach
and record the response then wash.
5- Add 0.2ml atracurium, no wash and wait 2 min, add 0.2 ml Ach
and record the response.
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