Practical pharmacology. Part 5. Dose response curve of acetylcholine

1.

Practical pharmacology
Part 5

2.

Dose response curve of acetylcholine
In the presence of atropine

3.

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.

4.

OUR ISOLATED ORGAN
Rabbit intestine
Tyrode‘s solution
Temperature 37˚C
Aeration by air pump

5.

0.1 ml

6.

0.2 ml

7.

0.3 ml

8.

0.4 ml

9.

0.1 ml
atropine

10.

0.1 ml
atropine

11.

0.2 ml
Ach.

12.

0.4 ml
Ach.

13.

0.6 ml
Ach.

14.

0.8 ml
Ach.

15.

1 ml
Ach.

16.

Now we need to draw the dose response curve

17.

Ach. only
0.1 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

18.

convert volumes into doses
0.1 g%
0.1 g
100 ml
x
0.1 ml

19.

x =
0.1 x 0.1
100
= 0.0001 g
= 0.1 mg

20.

Now draw your curve

21.

Response (cm)
Ach.+atropine
Ach.
Dose (mg)

22.

Conclusion

23.

Atropine is a reversible competitive muscarinic
receptor antagonist causing parallel rightward
shift of dose response curve of acetylcholine
Atropine decrease potency of acetylcholine
and not affect efficacy

24.

Notes

25.

Do not forget your tools

26.

Complete your book

27.

Thank you