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Why Guinea pig ileum is used?

313PHL Lab #4 Identification of effect and site of action of an unknown drug using isolated guinea-pig ileum. Guinea pig ileum is a smooth muscle receive dual nerve supply from autonomic nervous system (sympathetic and parasympathetic) .

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Why Guinea pig ileum is used?

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  1. 313PHLLab #4Identification of effect and site of action of an unknown drug using isolated guinea-pig ileum

  2. Guinea pig ileum is a smooth muscle receive dual nerve supply from autonomic nervous system (sympathetic and parasympathetic) . • Parasympathetic tone is dominant in ileum which Ach cause contraction by stimulating M3-R .

  3. Why Guinea pig ileum is used? • No myogenic contraction so any drug induce contraction can be seen. • Very sensitive to histamine unlike the rabbit due to the presence of histaminase enzyme.

  4. Types of receptors present in guinea-pig ileum • Cholinergic receptors . • Serotonergic or tryptaminergic receptors (5-HT1→5-HT7) . • Histaminergic receptors . • Adrenergic receptors .

  5. Types of receptors in guinea-pig ileum: 1- Cholinergic receptors:

  6. Types of receptors in guinea-pig ileum: 2-Serotonergic or tryptaminergic (5-HT )receptors : Serotonin = 5-HT(5-hydroxytryptamine) . 5-HT2A receptor found in smooth muscle and bronchi .

  7. Types of receptors in guinea-pig ileum: 3- Histaminergic receptors: Histamine is an autacoids naturally occurring in the body .

  8. Types of receptors in guinea-pig ileum: 4- Adrenergic receptors:

  9. Types of drugs act on guinea-pig ileum : Spasmogens: 1- Cholinergic stimulants , e.g. Ach . MOA : 2- Histaminergic stimulants, e.g. Histamine . MOA: histamine act on H1 R which coupled with Gαq → stimulate PLC → Hydrolysis of (PIP2) into: 1- DAG → ↑opening of Ca+2 channels 2- IP3 → mobilization of Ca+2 from its stores 1&2 → ↑ intracellular Ca+2 → Contraction .

  10. Spasmogens: 3- Serotonergic stimulants . e.g. Serotonin. 4- Direct acting stimulants (spasmogens) . e.g. Barium chloride, Calcium chloride .

  11. Spasmolytics : 1- Direct acting Spasmolytics . e.g. Mgcl2 Papaverine

  12. ExperimentIdentification of effect and site of action of an unknown drug using isolated guinea-pig ileum Blocker + Agonist + Unknown Unknown Agonist

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