Pharmacology Chapter 2: Drug-Receptor Interactions

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Questions and Answers

What is the term for the movement of drugs through the body?

Pharmacokinetics

What is the term for the body's biological response to drugs?

Pharmacodynamics

What is the role of a receptor in a drug-receptor interaction?

To act as a signal detector

What type of molecule can act as a receptor?

Any biologic molecule that binds to a drug and produces a measurable response Signup and view all the answers

What is the effect of an agonist on a receptor?

It converts an inactive receptor to an active receptor Signup and view all the answers

What is the effect of an antagonist on a receptor?

It blocks the receptor, keeping it in an inactive state Signup and view all the answers

What determines the magnitude of the cellular response to a drug?

The number of drug-receptor complexes Signup and view all the answers

What is signal transduction in the context of drug-receptor interactions?

The process by which a drug signal is converted into a cellular response Signup and view all the answers

Do all drugs exert their effects by interacting with a receptor?

No, not all drugs exert their effects through receptor interactions Signup and view all the answers

What is the primary difference between an agonist and a partial agonist?

The number of receptors they activate Signup and view all the answers

What is the term for the process by which repeated stimulation of a receptor leads to a diminished response?

Desensitization Signup and view all the answers

What is the role of G proteins in signal transduction?

To amplify the signal intensity Signup and view all the answers

What type of receptor is insulin an example of?

Enzyme-linked receptor Signup and view all the answers

What is the term for the process by which receptors are removed from the surface of the cell, making them unavailable for further agonist interaction?

Down-regulation Signup and view all the answers

What is the purpose of signal amplification in signal transduction?

To amplify the signal intensity and duration Signup and view all the answers

What is the effect of phosphorylation on receptors?

It desensitizes the receptor Signup and view all the answers

What type of receptor is dopamine an example of?

Transmembrane G protein-coupled receptor Signup and view all the answers

What is the term for the complex formed between a drug and a receptor?

Drug-receptor complex Signup and view all the answers

What is the primary factor that determines the magnitude of the drug effect in a dose-response relationship?

Receptor sensitivity to the drug Signup and view all the answers

What is the term used to describe the amount of drug necessary to produce an effect?

Potency Signup and view all the answers

What is the relationship between the concentration of free drug and the concentration of bound drug in a dose-response relationship?

[D] = [DR] / Kd Signup and view all the answers

What is the term used to describe the maximal effect of a drug in a dose-response relationship?

Emax Signup and view all the answers

What is the assumption required for the law of mass action to be applied to drug concentration and response?

The response must be graded and dose-dependent Signup and view all the answers

What is the term used to describe the number of drug-receptor complexes formed in a dose-response relationship?

Receptor binding Signup and view all the answers

What is the equilibrium dissociation constant for the drug from the receptor?

Kd Signup and view all the answers

What is the relationship between the concentration of the drug and the effect of the drug in a dose-response relationship?

E = [D] / [Emax] Signup and view all the answers

What is the primary factor that determines the efficacy of a drug in a dose-response relationship?

Intrinsic activity of the drug Signup and view all the answers

What is the relationship between the amount of receptors occupied by drug 2 and the magnitude of the response?

The magnitude of the response is proportional to the amount of receptors occupied Signup and view all the answers

What happens to the Emax when all receptors are bound?

Emax occurs Signup and view all the answers

What is the binding ratio of one molecule of drug to one molecule of receptor?

One molecule of drug binds to one molecule of receptor Signup and view all the answers

What is the characteristic of a full agonist?

Has intrinsic activity equal to one Signup and view all the answers

What is the effect of a partial agonist even when all receptors are occupied?

It can produce a lower Emax than a full agonist Signup and view all the answers

What is the characteristic of an inverse agonist?

Has intrinsic activity less than zero Signup and view all the answers

What is the effect of a competitive antagonist on the EC50?

It increases the EC50 Signup and view all the answers

What is the effect of an irreversible antagonist on the Emax?

It decreases the Emax Signup and view all the answers

What is the therapeutic index (TI) in the context of drug-receptor interactions?

The ratio of the dose that produces toxicity in half the population to the dose that produces a clinically desired response in half the population Signup and view all the answers

Pharmacodynamics is the study of the body's ______ response to drugs.

biological Signup and view all the answers

Drugs act as ______, receptors are signal detectors.

signals Signup and view all the answers

The magnitude of the cellular response is proportional to the number of ______ complexes.

drug-receptor Signup and view all the answers

A receptor is ANY biologic molecule to which a drug binds and produces a measurable ______.

response Signup and view all the answers

An antagonist blocks the receptor, keeping it in an ______ state and preventing it from binding and being converted to an active state.

inactive Signup and view all the answers

A ______ agonist is similar to an agonist, but with fewer activated receptors

partial Signup and view all the answers

The ______–receptor complex is formed during Signal Transduction

drug Signup and view all the answers

The ______ is part of Signal Transduction and is responsible for amplifying the signal intensity and duration

signal cascade Signup and view all the answers

Desensitization and ______ of receptors can occur due to repeated stimulation

down-regulation Signup and view all the answers

Examples of Transmembrane ______-gated ion channels include Acetylcholine and Nicotine

ligand Signup and view all the answers

Estrogen and Glucocorticoids are examples of ______ receptors

intracellular Signup and view all the answers

Refractory requires a ______ Relationships

Dose-Response Signup and view all the answers

The magnitude of the drug effect is determined by the ______ sensitivity to the drug and the drug concentration at the receptor site.

Receptor Signup and view all the answers

The ______ of the drug is the concentration of drug producing 50% of the maximum effect.

EC50 Signup and view all the answers

______ is the magnitude of response a drug causes when it interacts with a receptor.

Efficacy Signup and view all the answers

______ is a measure of the amount of drug necessary to produce an effect.

Potency Signup and view all the answers

______ is the maximal effect of the drug in a dose-response relationship.

Emax Signup and view all the answers

The magnitude of the response is proportional to the amount of receptors occupied by ______.

drug 2 Signup and view all the answers

The Emax occurs when all receptors are ______.

bound Signup and view all the answers

One molecule of ______ binds to only one molecule of receptor.

drug Signup and view all the answers

Full agonists produce a maximal ______ response.

biologic Signup and view all the answers

Partial agonists cannot produce the same ______ as a full agonist.

Emax Signup and view all the answers

The therapeutic index is the ratio of the dose that produces ______ in half the population to the dose that produces a clinically desired or effective response in half the population.

toxicity Signup and view all the answers

What is the primary function of β-adrenergic receptors in cardiac cell membranes?

To respond to epinephrine or norepinephrine Signup and view all the answers

What is the effect of an agonist on the receptor equilibrium?

It shifts the equilibrium towards the active state Signup and view all the answers

What is the characteristic of a partial agonist?

It shifts the equilibrium towards the active state, but to a lesser extent than an agonist Signup and view all the answers

What determines the magnitude of the cellular response to a drug?

The fraction of active receptors (R*) Signup and view all the answers

What is the role of antacids in the body?

They chemically neutralize excess gastric acid Signup and view all the answers

What is the definition of a receptor?

Any biologic molecule that produces a measurable response to a drug Signup and view all the answers

What is the effect of an antagonist on the receptor equilibrium?

It shifts the equilibrium towards the inactive state Signup and view all the answers

What is the characteristic of cardiac cell membranes?

They contain both β-adrenergic and muscarinic receptors Signup and view all the answers

What is the primary function of ligand-gated ion channels in neurons and muscle cells?

To mediate neurotransmission and muscle contraction Signup and view all the answers

What is the role of the α subunit in G protein–coupled receptors?

It binds to GTP Signup and view all the answers

What is the effect of DAG on protein kinases in G protein–coupled receptors?

It activates protein kinase activity Signup and view all the answers

What is the characteristic of enzyme-linked receptors?

They undergo conformational changes when activated by a ligand Signup and view all the answers

What is the primary difference between hydrophilic and hydrophobic ligands?

Their route of entry into the cell Signup and view all the answers

What is the effect of activation of the nicotinic receptor by acetylcholine?

It increases sodium influx and potassium outflux Signup and view all the answers

What is the role of the β and γ subunits in G protein–coupled receptors?

They anchor the G protein in the cell membrane Signup and view all the answers

What is the effect of activation of the GABA receptor by an agonist?

It increases chloride influx Signup and view all the answers

What is the characteristic of ligand-gated ion channels?

They are found on the cell surface Signup and view all the answers

What is the effect of local anesthetics on voltage-gated ion channels?

They inhibit sodium influx Signup and view all the answers

Study Notes

The Drug-Receptor Complex

Cells have multiple receptors, each specific to a particular agonist and producing a unique response.
The magnitude of the cellular response is proportional to the number of drug-receptor complexes formed.
This concept is analogous to the formation of enzyme-substrate complexes.

Receptor States

Receptors exist in at least two states: inactive (R) and active (R*), which are in reversible equilibrium with each other.
Binding of agonists causes the equilibrium to shift from R to R*, producing a biological effect.
Antagonists bind to the receptor but do not increase the fraction of R*, instead stabilizing the fraction of R.
Partial agonists shift the equilibrium from R to R*, but the fraction of R* is less than that caused by an agonist.
The magnitude of the biological effect is directly related to the fraction of R*.

Major Receptor Families

There are four major receptor families: ligand-gated ion channels, G protein-coupled receptors, enzyme-linked receptors, and intracellular receptors.
Hydrophilic ligands interact with receptors on the cell surface, while hydrophobic ligands interact with receptors inside cells.

Ligand-Gated Ion Channels

These receptors contain the drug-binding site in the extracellular portion.
The channel is usually closed until the receptor is activated by an agonist, which opens the channel for a few milliseconds.
Examples of ligand-gated ion channels include nicotinic receptors, which mediate neurotransmission and muscle contraction, and GABA receptors, which mediate neuronal inhibition.

G Protein-Coupled Receptors

These receptors contain the ligand-binding site in the extracellular portion and interact with G proteins in the intracellular portion.
Binding of an agonist to the receptor increases GTP binding to the α subunit, causing dissociation of the α-GTP complex from the βγ complex.
The α and βγ subunits interact with specific cellular effectors, such as adenylyl cyclase, phospholipase C, and protein kinases, to produce a signal cascade effect.

Enzyme-Linked Receptors

These receptors undergo conformational changes when activated by a ligand, resulting in increased intracellular enzyme activity.
Examples of enzyme-linked receptors include growth factors and insulin, which possess tyrosine kinase activity.
Activation of these receptors leads to a signal cascade effect, similar to G protein-coupled receptors.

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