1. 313 PHL Lab # 3
Effect of Certain Agonists & Their Antagonists on The Isolated Rabbit Intestine

2. Effect of stimulant drugs (spasmogens)and their blocker:
1-Drugs act on neuronal nicotinic (Nn) Receptors:
Agonist
Dil. Nicotine (0.01%, 0.1ml)
Antagonist :
Conc. Nicotine (0.1%, 0.1ml)
2-Drugs act on muscarinic (M3) Receptors:
Ach (0.01%, 0.1ml)
Atropine (0.1ml, 0.1%)

3. 1-Drugs act on neuronal nicotinic (Nn) Receptors:
Agonist
Dil. Nicotine (0.01%, 0.1ml)
MOA:
Dil. Nicotine act on Nn receptor
→ activates Na-K channels
→ rapid ↑ intracellular Na
→ rapid depolarization
→ increase contraction .

4. Antagonist : Conc. Nicotine (0.1%, 0.1ml)
- Conc. Nicotine is depolarizing ganglionic blocker
MOA:
It causes an initial increase in amplitude due to its initial depolarization (↑contraction)
→ Followed by successive depolarization
→ transmission failure & muscular fatigue (blocker of the receptors) .

5. 2-Drugs act on muscarinic (M3) Receptors:
Agonist :
Ach (0.01%, 0.1ml)
MOA :
Ach stimulates M3R
→ ++ Phospholipase C
→ Hydrolysis of (PIP2) into:
1- DAG → opening of Calcium channels → Ca++ influx → contraction
2- IP3 → mobilization of ca++ from its stores
↑ intracellular calcium →contraction

6. Antagonist:
Atropine (0.1ml, 0.1%)
MOA:
It is a reversible, competitive, specific, non-selective muscarinic blocker.