Receptor Theories Flashcards
Define occupation theory.
Drugs act on independent binding sites and
activate them.
Results in a biological response that is
proportional to the amount of drug-receptor complex formed.
What is drug effect directly proportional to?
The number of receptors occupied.
Explain rate theory
The response is proportional to the rate of drug-Receptor
complex formation.
What is pharmacological activity directly proportional to as stated by the rate theory?
Pharmacological activity is directly proportional to
the rates of dissociation and association - not number of receptors occupied.
Describe the association of an agonist.
drug with fast association & fast dissociation
Describe the association of partial agonist.
Drug with intermediate association & intermediate dissociation
Describe the association of an antagonist.
Drug with fast association and slow dissociation
Describe the induced-fit theory.
As the drug approaches the receptor, the receptor alters the conformation of its binding site to produce drug—receptor complex.
Describe macromolecular perturbation theory.
Suggests that when a
drug- receptor interaction occurs, one of two general types of macromolecular perturbation is possible:
1. a specific conformational perturbation leads to a biological
response (agonist),
2. whereas a non specific conformational perturbation leads to no
biologic response (antagonist).
Explain the activation-aggregation theory?
Suggests that a drug
receptor (in the absence of a drug) still exists in an equilibrium between an activated state (Bioactive) and an inactivated state
(Bio-inactive).
Describe the two state receptor model.
A receptor, regardless of the presence or absence of a ligand, exists in two distinct states: the R (resting state) and R* (activated state) states, which are in equilibrium with each other.
Describe the equilibrium when no ligand is present (two state receptor model)
The equlibrium lies far to the left, and few receptors are found in the R* state.
Describe the affinity for an agonist in the two state receptor model.
Has high affinity for the R* state than for the R and will shift equilibrium to the right (R*)
Describe the affinity for an antagonist in the two state receptor model.
An antagonist has equal
affinity for R and R* so does not affect the equilibrum.
Describe the affinity for inverse agonists in the two state receptor model.
Inverse agonists have affinity for R.
