Receptor theory 2 Flashcards
What is intrinsic activity?
The maximal response expressed as a fraction of the maximal response for the entire system.
What is affinity?
The strength of an interaction between a drug and a receptor.
What forces control affinity?
Electrostatic, hydrogen bonding, Van der Waals forces and hydrophobic bonds.
What is the equation for the fraction of maximal binding?
[AR] (amount of drug receptor complex)/{Rt} (total no. of receptor sites) which is equal to the conc. of drug/conc. of drug + dissociation constant.
What is the agonist binding theory?
The binding of a ligand to a receptor is assumed to follow the Law of Mass Action according to the langmuir adsorption isotherm as defined by Clark.
What is the Langmuir adsorption isotherm?
The concept of binding area for agonists to receptors, involving factors such as the total area available for binding, area already bound, rate of diffusion towards the surface and rate of adsorption.
What type of relationship is present between receptor occupancy and tissue response?
It is non-linear - hyperbolic.
What is the magnitude of receptor reserve dependent on?
The efficacy of the agonist.
What is constitutive activation?
The concept that some receptors (such as benzodiazepines, cannabinoids and dopamine) have a basal level of activation even when no ligand is bound.
What are inverse agonists?
Ligands that reduce the level of constitutive activation. They bind the same way as agonists but reduce activation.
What is the effect of an inverse agonist and an antagonist?
A higher concentration of inverse agonist is needed to cause a reduce in receptor activation - the antagonist prevents the action of the inverse agonist.
What is the concept of the two state model receptor activation model?
An equilibrium lies between the resting and activated state of receptors. The binding of agonists or antagonists just shifts this equilibrium.
