Pharmacodynamics Flashcards
what is pharmacodynamics?
the study of the PHYSIOLOGICAL and BIOCHEMICAL interactions of drug molecules with their target tissues/receptors responsible for their ultimate drug effects
What is a ligand?
any molecule that binds to a receptor
what is a drug?
an exogenous ligand
What are some endogenous ligands?
neurotransmitters, hormones, peptides
What is a receptor?
protein molecule on cell surface or within the cell that is the initial site of action of a biological agent (neurotransmitters, hormones, peptides, drugs)
TRUE or FALSE: biological agents are endogenous ligands
FALSE: endogenous and exogenous
What are the criteria for defining a receptor?
saturability, specificity, and reversibility
What can be used to reveal the saturability of a receptor?
Dose-response
TRUE or FALSE: In terms of saturability, there are a finite number of receptors per cell.
TRUE
Describe the specificity of a receptor.
high binding affinity necessary to elicit a biological response
Describe the reversibility of a receptor.
- binding to receptors should be reversible
- ligand should be DISSOCIABLE and RECOVERABLE
Reversibility distinguishes ______________ interactions from ______________ interactions.
receptor-ligand; enzyme-substrate
TRUE or FALSE: The saturability of a receptor remains constant over time.
FALSE: saturability can change over time
What kind of ligands do extracellular receptors bind? What is an example?
- water-soluble ligands
- e.g. neurotransmitters
What kind of ligands do intracellular receptors bind? What is an example?
- lipid-soluble ligands within the cell
- e.g. steroid hormone receptors
Extracellular receptors are a common target for _____________.
psychoactive drugs
Intracellular receptors are a common target for _____________ and _________________.
steroid hormones; lipophilic compounds
what are the mechanisms of signalling for extracellular receptors?
- ligand-gated ion channels
- G-protein coupled receptors (GPCR)
- receptor kinases
What is an example of ligand-gated ion channels?
postsynaptic neurotransmitter receptors
What is an example of GPCR? What mechanism do they involve?
- metabotropic receptors
- intracellular second messenger (mechanism)
What are receptor kinases common for?
cytokine and peptide hormone receptors (e.g. insulin)
Where are intracellular receptors located?
in the cytoplasm
Are hormone receptors intracellular or extracellular?
intracellular
Where do hormone receptors translocate to upon hormone binding?
to the nucleus
What is the function of hormone receptors?
function as transcription factors
TRUE or FALSE: GPCRs directly induce changes in gene expression by binding to specific response element
FALSE: hormone receptors
What is the key to receptor function?
specific recognition of ligand
What are agonist interactions?
elicit a biological effect on the receptor
What are antagonist interactions?
prevent or block a biological effect
What is another term used to define potency?
ED50
What is ED50?
the dose required to elicit a half-maximal effect
Agonist activity at a receptor can be measured by examining the __________.
dose-response
TRUE or FALSE: with increasing concentration of agonist, the biological response is lower.
FALSE: increase the dose, increase the response
What kind of shape does the dose-respond follow?
sigmoidal
What is the difference between potency and efficacy?
- potency depends on ED50
- efficacy depends on the maximum response
What is TD50 a measure of?
potency of a drug at eliciting a toxic response