quiz4c - 3. The IC 50 values for bromocriptine to bind to...

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Quiz 4c - Gville True/False (2 pts. each) You have shown that the following drugs all can affect the production of cAMP: bromocriptine, quinpirole, Drug S and Drug X, but muscimol has no effect (see Figure 1 next page). You have also measured and compared the efficacies and potencies of these drugs to displace the specific binding of 3 H-DA from homogenized brain samples (see Figure 2). Only 70% of the receptors occupied by 3 H-DA can bind Drug S (Subtype S) while only 30% of the receptors can bind quinpirole (subtype Q). Therefore, we conclude that there are two subtypes of DA receptor. Which of the following conclusions are true? If you don’t have any evidence to prove that the statement is true, then answer false. 1. Bromocriptine has a higher affinity for the "Q" site compared to it’s affinity for the “S” site. 2. Bromocriptine binds to both “Q” and “S” receptor subtypes but SKF does not.
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Unformatted text preview: 3. The IC 50 values for bromocriptine to bind to both receptor subtypes are not very close together (more than 10-fold different). 4. Agonists for the "Q" subtype of dopamine receptors decrease intracellular cAMP by positively activating that receptor subtype. 5. Drug X is a partial agonist at Q receptors. 6. Muscimol is an antagonist at S receptors. 7. Quinpirole is an inverse agonist for the "Q" subtype of dopamine receptors. Figure 1. Figure 2. 20 40 60 80 0.01 0.03 0.1 0.3 1 3 10 30 100 300 1000 3000 Drug Concentration (nM) Intracellular cAMP levels (nM) Bromo. X Quin. Musc. SKF 10 20 30 40 50 60 70 80 90 100 0.01 0.03 0.1 0.3 1 3 10 30 100 300 1000 3000 Competing Drug concentration (nM) % Specific 3H-DA Binding Muscimol Bromo. Quin. X SKF...
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quiz4c - 3. The IC 50 values for bromocriptine to bind to...

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