Agonist Ach Case Study

DISCUSSION

The response of the guinea pig ileum to agonist ACh was a proportional contraction of smooth muscle to the increase dosage shown in Figure 1 and Table 1. From figure 1, in lower concentrations of ACh in the presense of Atr, there was a lower dose response, suggesting Ach is no longer in a non-competitive environment. Both curves from the dose responses (Figure 1) reach 100% maximum response even in the presence of Atr, showing a rightward parallel shift, indicates the agonist efficacy was not affected by the presence of the competitive antagonist (Neal, 2009). The EC50¬¬ of ACh also increased in the presence of Atr, indicating ACh is acting as a competitive antagonist, thus showing that Atr reduced its potency of ACh. This occurs

Agonist Ach is used by the parasympathetic nervous system to activate muscarinic and nicotine receptors and can each preferentially interact one of the two types of receptors. Atropine specificity is it action to act as the antagonist of acetylcholine (ACh), inhibiting the muscarinic actions of ACh on the structures innervated by the vagus nerve.

3. What type of antagonism does atropine display at the muscarinic receptor? What is meant by EC50? Describe the change to EC50 in your experiment in the presence of atropine. What is the purpose of the Schild plot?

Atropine displays a competitive, reversible antagonism on the muscarinic acetylcholine receptors. The concentration of the agonist that gives a half maximal response from the binding (EC50) is where the response is reduced by half. The EC50¬¬ of ACh also increased in the presence of Atr, indicating that Atr reduced the potency of ACh.

The Schild plot is a method of receptor classification, measuring the affinity of antagonists to its receptors given that the antagonist is competitive. It gives a fitted regression line, which is used to estimate the pA2, the negative log of antagonist concentration, which provides 2-fold shift in