Pharmacy

1. •
Pharmacology 1 (PO502)
•
Fall 2022/2023
Lab 7
Faculty of Pharmacy
Department of Pharmacology
& Toxicology

2. Determination of the site of action
of
Different cardiac stimulant &
depressant drugs
using
Isolated Frog Heart

3. M2
NN
NN
1
Drugs
Depressants Stimulants
Nn agonist (e.g. Dil. nicotine) β-agonist (e.g. Isoprenaline)
M agonist (e.g. Ach) Direct stimulant
Direct depressant H2 receptor stimulant (histamine)

4. Setup

5. -ve chronotropic
-ve chronotropic
-ve inotropic
-ve inotropic
Depressants
Stimulants
+ve chronotropic
+ve chronotropic
+ve inotropic
+ve inotropic

6. Agonists and blockers used in the
experiment
Receptor Agonist Blocker
β Isoprenaline Propranolol
Nn Dil. nicotine
NLD
chlorisondamine
M Ach Atropine

7. Steps to test if a drug acts on a
certain receptor
UNK
AGONIST AGONIST
BLOCKER
Start
If no
action 
Unk acts
on the
blocked
receptor
If there is
still action
 Unk
doesn’t act
on the
blocked
receptor
 Test
another
receptor
(if
possible)

8. Why is the agonist added after the
blocker?
To test for complete blockade of the
receptor.
Why is the agonist added before the
blocker?
To test for the sensitivity of the receptor
to the added agonist.

9. PROCEDURE
1. A toad is pithed, its chest is opened and a cannula is
introduced in the sinus venous .
2. The heart is removed out of the toad and perfused
through the cannula by Ringer’s solution.
3. Cardiac contractions are recorded on a drum.
4. There is no need to maintain the perfusion fluid at a
constant temperature because the toad is a cold
blooded animal.

10. a) If the unk is stimulant:
- Add Isoprenaline
- Add the following 3 consecutively
No stimulation 
Unk is β agonist
Stimulation 
Unk is directly acting
Prop Isop Unk

11. Unk is
DIRECT
Unk is
β1
agonist
Unk Isop
Prop
Isop
Unk

12. b) If the unknown is depressant:
 Test for nicotinic action:
- Add dil. Nicotine
- Add the following 3:
No depression 
Unk is Nn agonist
Depression 
continue the experiment
NLD Dil. nic. Unk

13.  Test for muscarinic action:
- Add Ach
- Add the following 3:
No depression 
Unk is M agonist
Depression 
Unk is directly acting
Atrop. Ach Unk

14. 0.1
Dil. Nic.
0.1
NLD
0.1
Dil. Nic
0.1
Unk
0.1
Unk
Site of action:
Nicotinic agonist
Unknown may be Dil nicotine

15. 0.1
Dil. Nic.
0.1
NLD
0.1
Dil. Nic.
0.1
Unk
0.1
Unk
0.1
ACh
0.1
Atrop
0.1
ACh 0.1
Unk
Site of action:
Muscarinic agonist
Unknown may be ACh

16. 0.1
Ach
0.1 NLD 0.1
Atrop
0.1
Unk
0.1
Dil. Nic.
0.1
Dil. Nic.
0.1
Unk
0.1
ACh 0.1
Unk
Site of action:
Direct acting Depressant

17. Examples

19. The unknown drug is ……………

20. The unknown drug is ……………

21. The unknown drug is ……………

23. The unknown drug produces cardiac stimulation
via activation of which receptors?.....................

24. The unknown drug is ……………

25. The unknown drug is ……………

26. Thank you