31320phl (2). Intro Neuroendocrinology ppt

Does response curve

1. 313PHL
Lab #1
Introduction & Dose Response Curve of
Different Doses of Acetylcholine

2. Purpose of Pharmacological Experiments :
The pharmacological experiments largely divided
in to :
Qualitative :
-To determine ( analyze) the activity of drug (i.e. analgesic,
hypotensive and hypoglycemic).
-To determine mechanism of drugs action.
Quantitative:
To assay (measure) the potency of drugs (e.g. toxic level, therapeutic
level, LD50).

3. Types of pharmacological experiments :
A-In vitro experiments
-Study the action of drugs on isolated preparation:
1) Tissue e.g. (intestine, ileum) .
2)Organ e.g. (heart) .
•Advantages:
-Easier to study MOA (qualitative) .
-Easier to study its potency (quantitative) e.g. DRC on rectus
abdominis.
•Disadvantages :
-There is no interference by compensatory mechanisms of body
that may affect the direct action of drug not easy to study the
chemical and biological effect of the drug.

4. B-In vivo experiments
-Study the action of drugs on the whole body (intact) .
•Advantages:
-Observe the direct drug action(actual effect) .
-Easier to study the chemical and biological effect .
•Disadvantages :
-Difficulty to determine the exact mechanism of action .

5. In vitro experiments
1) Experimental conditions:
An isolated organ or muscle should be bathed in a suitable media that
is resemble to the normal condition in the body regarding
(pH,osmolarity,temperature) .
Therefore, tissue is bathed in solutioncontaining:
.1-Electrolytes
2-Nutrients .
.3-Adjusted Physiological pH
.4-Constant temperature
5-Aeration .

6. :2) Physiological Salt Solution
•According to different tissue to be used, there is a different
physiological solutionprepared.
•But all or most of them contain the following ingredients at different
concentrations:
1-Nacl→ to adjust the isotonicity.
2-Glucose → nutrient .
3-Ca+2, K+, sometimes Mg+2 as CL salt → to maintain normal
muscle contraction.

7. 3-Sodium bicarbonate → to adjust pH similar to that of blood .
4-NaH2PO4 (sodium di hydrogen phosphate) buffer→ to
compensate for any change in pH .
The two most commonly used physiological solutions are Tyrode’s
and Krebs .

8. 3) Aeration:
Physiological salt solutions should be aerated by a suitable gas :
1-Pure oxygen → for hearttissues.
2-Normal air → for intestine.
3-Carbogen (95% O2, 5% CO2) → used for uterus.

9. 3)Temperature:
•Mammalian tissue must be bathed in a warmed solution adjusted
at 37ºCe.g. Isolated rabbit intestine .
•The temperature should be decreased in some experiments to
reduce the myogenic contraction, the warmed solution adjusted at
32ºCe.g. Guinea-pig ileum.
•Amphibian tissues survive at room temperature (25ºC)e.g.frog
rectus abdominis .

10. Dose cycle & contact time
Dose cycle (NT): the time between different drugs addition.
Contact time (CT): the duration of drug presence in the organ bath
until its removal by washing .
•CT= 30 sec, NT=60 sec, washing 3 times 30 sec for each total
cycle time = 3 min.

11. Apparatus for experiments with isolated
amphibian and mammalian tissue:
Physiograph and thermostatically controlled organ bath.
Drugs acting on the isolated tissue:
•isolated rabbit intestine has normal myogenic contraction which
is under the control of the Autonomic nervous system (ANS).
•The effect of drugs that act on the intestine could be a
stimulatoryi.e. increase in the intestinal contraction or
inhibitoryi.e. decrease in the intestinal contraction.

12. The intestine innervated by ANS :
Sympathetic
Transmitter:noradrenalin
mainly, Adrenaline .
Receptors present in
(intestine): Adrenergic:
α1,B2
Action:
inhibitory (↓contraction)
relaxation .
Parasympathetic
Acetylcholine (Ach) .
Cholinergic:
Central:Nicotinic (Nn) .
and peripheral: muscarinic
(M3)
excitatory
(↑contraction)
contraction

13. •This increase or decrease in muscle contraction is
observed as follows:
↑ amplitude ↓ amplitude

14. •Or
↑ tone ↓ tone

15. •Or
↑ tone & amplitude ↓ tone & amplitude

16. The effect of different doses of acetylcholine on smooth
muscle of intestine:
N 0.05 0.1 0.2 0.3 0.4
Ach Ach Ach Ach Ach