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Practical pharmacology. Part 5. Dose response curve of acetylcholine
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Practical pharmacologyPart 5
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Dose response curve of acetylcholineIn the presence of atropine
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PRINCIPLE :Atropine is a competitive
antagonist for Ach on
muscarinic receptors (M)
of the isolated rabbit
jejunum.
Higher concentrations of
Ach are needed to displace
atropine from M receptors
and eliciting a response.
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OUR ISOLATED ORGANRabbit intestine
Tyrode‘s solution
Temperature 37˚C
Aeration by air pump
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0.1 ml6.
0.2 ml7.
0.3 ml8.
0.4 ml9.
0.1 mlatropine
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0.1 mlatropine
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0.2 mlAch.
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0.4 mlAch.
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0.6 mlAch.
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0.8 mlAch.
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1 mlAch.
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Now we need to draw the dose response curve17.
Ach. only0.1 ml
0.2 ml
0.3 ml
0.4 ml
Ach. +
atropine
0.2 ml
0.4 ml
0.6 ml
0.8 ml
1 ml
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convert volumes into doses0.1 g%
0.1 g
100 ml
x
0.1 ml
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x =0.1 x 0.1
100
= 0.0001 g
= 0.1 mg
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Now draw your curve21.
Response (cm)Ach.+atropine
Ach.
Dose (mg)
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Conclusion23.
Atropine is a reversible competitive muscarinicreceptor antagonist causing parallel rightward
shift of dose response curve of acetylcholine
Atropine decrease potency of acetylcholine
and not affect efficacy