Toxicology

1. Determination of Pharmacological Effect of the
Drug
In vivo Study :
• Examination of the drug effect in an ' INTACT ' animal .
• like : frog- rat - mouse - guinea pig
In vitro study:
• Study the drug effect on an isolated organ that kept alive outside the
body.
• Like : frog rectus abdominis - rabbit intestine

2. Isolated organ preparation
The used isolated organ
preparations:
• Frog rectus abdominis
• Rabbit intestine
The used devices
(kymograph)

3. A) Separating Funnel :
• Also called reservoir :
as it is where the physiological solution is
stored.
Types of Physiological solutions :
1) Ringer’s solution :
suitable for the Frog rectus abdominis .
2) Tyrode’s solution :
suitable for Rabbit intestine.

4. The components of these
physiological solutions :
1. Glucose :
nutrient and energy supplier
2. NaHCO3 or NaH2PO3 :
act as Buffer to adjust the pH.
3. NaCl , KCl , MgCl2 :
to adjust the isotonicity.
Both Ringer’s and Tyrode’s solutions contain
these components but with different concentrations.

5. B) Organ Bath :
•It is the place where the organ is
placed.
•Filled with the physiological solution
to a fixed level.
• “ tissue holder” – “O2-tube “
• Responsible for the aeration.
• A place where the muscle in hanged.
C) L-tube :

6. D) The Air Pump:
• It supplies the organ with O2 in a rate if 1
Bubble/sec.
• It is connected with the organ bath by ( L-
tube )
The Role of Aeration :
1) Provide the O2 source ( respiration –
contraction ) .
2) Essential for mixing.
3) Essential for washing.

7. E) Lever :
• For the magnification of the muscle contraction.
• Resting tension :
(piece of plasticine that weighs 1 gm )

8. F) Drum :
• On which magnification is seen.

9. Experiment I: Dose Response Curve of Acetylcholine
Using Frog Rectus Abdominis Preparation.
Principle:
• Frog rectus abdominis is a skeletal muscle, innervated by a somatic motor
nerve, that supplies the muscle with A.Ch.
• As a response to A.Ch., the muscle contracts due to the action of A.Ch. on
the nicotinic receptors.
• The response increases when the dose is increased until reaching the
maximum response

10. How is the maximum response reached ?!!

11. 1) Each muscle has a specific number of nicotinic receptors.
2) Upon the addition of small dose of Acetylcholine, it will occupy a part
of these receptors , and leading to muscle contraction.
3) Upon increasing the dose , more receptors will be occupied , leading
to more muscle contraction.
4) At a certain dose ( the maximum dose ) , all the receptors will be
occupied , so that the muscle will give its maximal contraction.
5) Increasing the dose above the maximum dose will not cause an
increase in the response , as no more receptors are available.

12. Procedure :
B) SEPARATION AND HANGING OF ONE MUSCLE.
ANY ONE REMEMBERS ??
A) PREPARATION OF FROG RECTUS ABDOMINIS

13. c) Starting the addition of the doses :
• Inject 0.1 ml of Acetylcholine
• Calculate the time elapsed from injection till reaching the plateau ( the contact time )
• Switch off the apparatus, start to wash the muscle
( do not forget to load down the resting tension during washing )

14. • Inject the second dose of Acetylcholine : 0.2 ml
• Wait for the same contact time as previous.
• Turn off the apparatus and start to wash the muscle .
• Repeat the steps with : 0.4 ml, 0.8 ml, and (1.6ml) .

15. How to measure the peak height :
Height = A-B

16. DOSE RESPONSE CURVE :
• Use the peak heights
to draw this table :
Use the table to draw the
Dose Response Curve
ml
Height