Pharmacology Pharmacodynamic Mechanisms 4

Question 1

Which second messenger is produced when Gs-coupled receptors activate adenylyl cyclase?

Accepted Answer

Cyclic AMP (cAMP)

Answer

Inositol trisphosphate (IP3)

Answer

Diacylglycerol (DAG)

Answer

Cyclic GMP (cGMP)

Question 2

Noncompetitive (insurmountable) antagonism is characterized by:

Accepted Answer

Reduction of Emax that cannot be overcome by increasing agonist dose

Answer

Rightward shift of the agonist curve with preserved Emax

Answer

Increased agonist affinity at saturating antagonist concentrations

Answer

Reversible binding that is displaced by excess agonist

Question 3

Which ion channel mechanism is responsible for the pharmacodynamic action of benzodiazepines?

Accepted Answer

Enhancement of GABA-A chloride channel opening frequency

Answer

Blockade of voltage-gated sodium channels

Answer

Inhibition of NMDA glutamate receptor activity

Answer

Activation of potassium leak channels

Question 4

Drug A has an EC50 of 2 mg/kg and Drug B has an EC50 of 20 mg/kg for the same endpoint. Which statement is correct?

Accepted Answer

Drug A is more potent than Drug B

Answer

Drug B is more potent than Drug A

Answer

Both drugs have equal potency

Answer

Potency cannot be determined from EC50 alone

Question 5

Receptor tyrosine kinase (RTK) signaling is most closely associated with:

Accepted Answer

Activation of intracellular kinase cascades (minutes)

Answer

Rapid ion flux changes (milliseconds)

Answer

Genomic transcription changes (hours to days)

Answer

Direct G-protein coupling

Question 6

The phenomenon of homologous desensitization of GPCRs specifically involves:

Accepted Answer

Phosphorylation by GRKs and beta-arrestin recruitment to the agonist-occupied receptor

Answer

Downregulation of all receptor types uniformly

Answer

Cross-phosphorylation by PKA of unoccupied receptors

Answer

Receptor internalization triggered by inverse agonists

Question 7

Which pharmacodynamic interaction occurs when two drugs together produce an effect less than additive?

Accepted Answer

Antagonism

Answer

Synergism

Answer

Potentiation

Answer

Tachyphylaxis