Agonist Drugs Flashcards
What is a receptor?
Protein target with which a naturally occurring chemical mediator binds specifically to initiate a cell response.
How does a cell surface receptor work?
Molecules which are too large or hydrophilic to enter the cell bind to receptors on the cell surface membrane.
How does an intracellular receptor work?
Molecules are small or hydrophobic enough to cross the membrane and activate a receptor within the cell itself.
What happens when a chemical mediator binds to a receptor?
It causes a shape change which stabilises the active form of the receptor and enhances the interaction with signal transduction mechanism.
What form of receptor is a beta1 adrenoceptor?
G protein coupled receptor.
What affects the response of a receptor to an agonist?
The drug concentration, drug affinity, intrinsic efficacy, nature of receptor and number of receptors.
What is occupancy?
The number of receptors filled by the drug.
What is the equation for occupancy?
Concentration of agonist in vicinity divided by (agonist conc plus Ka)
How does occupancy change as Ka increases?
As Ka gets bigger, the occupancy decreases.
When is Ka equal to the agonist concentration?
When half of receptors are occupied.
What is bioassay?
A method to predict physiological response of the body to drug, using a muscle or other tissue strip in an organ bath.
What is EC50?
Drug potency. The concentration needed to achieve 50% of the maximum response.
What is intrinsic efficacy?
The ability of an agonist on binding to activate a change in shape of the receptor.
What is the difference between a full and partial agonist?
A full agonist can achieve the maximum response, has an intrinsic efficacy value of +1. A partial agonist can’t achieve the full response, has a value somewhere between 0 and +1.
What is an inverse agonist?
An agonist which causes a negative shape change to receptor, causing it to be stabilised in the inactive state.
