Data analysis and interpretation (up to 1700 words):
Using the Virtual Organ Bath 2.8 software, you’ll study the effects of two different agonists (for example: acetylcholine & pilocarpine or carbachol) on the contraction of smooth muscle from guinea pig small intestine.
The effect of both drugs should be evaluated without and in the presence of one antagonist.
Set a list of concentrations for both acetylcholine and pilocarpine. With the help of dilution formula in the virtual organ bath software, work out the volumes required from the appropriate stock solutions.
Progressively increasing doses of the agonist should be added to the bath (use a range between 1×10-10 – 1×10-6 M) and contraction of the tissue (in gms) will be measured and recorded.
Afterwards, the appropriate antagonist (concentration in the reservoir 5×10-8 M) should be added, and the experiment is repeated using higher concentrations of the agonists (up to 1×10-4 M)
These tables are just an example of how you could record your data:
Dose used (without antagonist) Contraction Response in gms (unit) Acetylcholine Pilocarpine
Dose used (with antagonist 5×10-8 M) Contraction Response in gms (unit) Acetylcholine Pilocarpine
Your submitted work should include the following:
• A brief description of the design of the experiment and how the data was collected.
• Your data recorded in tables with concentration of both agonists and the
corresponding antagonist.
• Answer the following questions:
1. Discuss
• What is Acetylcholine and how does it produce contraction of the smooth muscle (dynamics: receptors, type and drug-receptor interaction)?
• What is pilocarpine (or carbachol if it was chosen in the experiment) ? what is its mechanism of action? discuss briefly its therapeutic applications
• Identify two drugs that can be used for their effect on smooth muscles within the body (urinary tract, blood vessels, or respiratory system) and briefly discuss the following:
– the mechanism of action
– drug-drug interaction
– therapeutic application
2. Using Excel, or Graphpad Prism:
• Convert the contraction values into %response and the dose into log10 for each drug
• Plot the following graphs :
o the %response vs. log10 dose for acetylcholine (with and without the antagonist, 2 curves in the same graph)
o the %response vs. log10 dose for pilocarpine or carbachol (with and without the antagonist, 2 curves in the same graph)
• Describe both graphs:
o Compare the 2 dose-response curves (without antagonists): which agonist is the most potent? And which one is the most effective? provide evidence from your data.
o Provide an approximate value of ED50 for both acetylcholine and pilocarpine or carbachol.
o Analyse the effect of the antagonists on the dose-response curves for both drugs. How would you describe the mechanism of action of the antagonist on the muscarinic receptors?
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