drug receptor interaction

Question 1

what is the importance of studying receptors

Answer 1

pharmaceutical industry and drug development

physiology of endogenous transmitters: transmitters and hormones act primarily upon receptor targets

chemical toxicity;many toxic mechanisms are receptor mediated

viral toxicity; viruses and other microorganisms can target receptors

Question 2

what are the types of receptors

Answer 2

ligand-gated ion channels(ionotropic receptors)
G-protein coupled receptors(metabotropic receptors)
tyrosine-kinase receptors
nuclear receptors

Question 3

what is an agonist

Answer 3

this is a drug that binds to a receptor, activates them and elicits a biological response

Question 4

what is a partial agoinist

Answer 4

a partial agonist is a drug that produces a biological response but never the maximal tissue capacity. it possesses antagonistic properties.

Question 5

what is an antagonist

Answer 5

this is a drug that blocks the action of an agonist commonly by binding to a receptor but never eliciting a biological response.

Question 6

what is an inverse agonist

Answer 6

this is a drug that produces an opposing effect of the biological response an agonist would produce.

Question 7

what is the affinity of a drug

Answer 7

this is the ability of an agonist to bind to a receptor. it is a measure of how tightly or loosely a drug binds to a receptor.

Question 8

what is the efficacy of a drug

Answer 8

this is the ability of a drug to elicit a biological response from a drug-receptor interaction. a full agonist has a higher efficacy than a partial agonist.

Question 9

what happens when an agonist is added to a population of receptors

Answer 9

the agonist binds to the receptors to form an agonist-receptor complex. what governs this binding is called affinity.

Question 10

what bonds can be formed between a receptor and a drug and a receptor

Answer 10

hydrogen bonding
ionic bonding
van der Waals forces
These three forces are relatively weak, are reversible binding, and have good dissociation

covalent bonding- has stable strong bonds, irreversible binding, poor dissociation and is very rare.

Question 11

how do most agonists bind to their receptors

Answer 11

reversibly

Question 12

what is the reversible binding of agonists governed by?

Answer 12

law of mass action

Question 13

what is the law of mass action

Answer 13

this law states that the reversibility of binding is dependent on the concentration of reactants involved.

Question 14

what does the law of mass action predict?

Answer 14

Low [A] - lots of Rfree - few AR interactions

Increase [A] - more AR interactions - reaction driven to right

Continue increasing [A] – few Rfree, the reaction reaches maximal

Question 15

what is Kd of a drug

Answer 15

each drug has its own Kd. the Kd of a drug is the conc of a drug where 50% of the max number of receptors are bound by the drug.

Kd is inversely proportional to affinity, the higher the affinity, the lower the Kd.

Question 16

what is Bmax

Answer 16

this is the max number of receptors bound by a drug.

Question 17

what is the threshold conc of a drug

Answer 17

this is the minimum conc of drug required to produce a pharmacological rrsponse

Question 18

what is EC50?

Answer 18

this is the conc of the drug required to produce 50% pharmacological response.it is used to deterine the potency of a drug; the higher the EC50, the less potent a drug is.

Question 19

What is the maximum pharmacological effect

Answer 19

Efficacy

Question 20

what is the potency of a drug

Answer 20

this refers to the concentration of a drug needed for a pharmacological effect to occur. the more conc needed, the less potent a drug is.

Question 21

why is only a small number of drug-receptor interactions able to produce biological effects?

Answer 21

because receptors amplify signals.

Question 22

explain buprenorphine action

Answer 22

buprenorphine is an opioid partial agonist which has a high affinity for the opioid receptor. it is used to help those with opioid addiction. it binds to the receptor thereby stopping opioids from binding to their receptors.

Question 23

what is a competitive antagonist

Answer 23

this is an antagonist that binds to the same site as an agonist. the agonist and competitive antagonist both bind reversibly. the agonist must increase in concentration to overcome the antagonist binding to the receptor. it is a surmountable antagonism

Question 24

what is a non-competitive antagonist

Answer 24

the antagonist binds to a different site from the agonist and cause a functional impairment of the receptor and as a result, the agonist is unable to bind to its receptor. here, the EC50 remains the same but efficacy is reduced.

Question 25

explain one clinical application of competitive agonist

Answer 25

naloxone which is used to treat opioid overdose: naloxone is a competitive agonist for opioid receptors. it has a stronger affinity for opioid receptors than the opioids so it knocks the opioids off the receptors for a short time (30-90mins) which allows the person to breathe again and reverse. the overdose