Drug Receptor Interaction

Question 1

why is it important to study drug receptors?

Answer 1

• drug development based in understanding receptors
• for chemical toxicity: toxic mechanisms are receptor mediated
• for viral toxicity: viruses and microorganisms can target receptors

Question 2

what are inotropic receptors and what are some examples?

Answer 2

• also known as ligand gated ion channels
• occurs in milliseconds (ms)

-Ach, nicotinic

Question 3

what are metabotropic receptors and what are some examples?

Answer 3

• also known as G protein coupled receptors
• occurs in seconds

-Ach, muscarinic

Question 4

how do ionotropic receptors work?

Answer 4

• channel only opens when a specific chemical binds to the receptors
• allows ions to enter/leave the cell
• leads to hyper/depopolarisation of the cell

Question 5

how do metabotropic receptors work?

Answer 5

• when chemical binds to receptor, causes cascade of 2° messengers
• will activate the G protein that inhibits/activates and enzyme
• can lead to phosphorylation, release of Ca2+ or induce opening of other ion channels
• leads to pharmacological response

Question 6

what is an agonist?

Answer 6

a drug that binds to receptor and illicit a biological response

Question 7

what is an antagonist?

Answer 7

• a drug that blocks the action of the agonist compound

- binds to the receptor w/o eliciting a biological response

Question 8

what is a partial agonist?

Answer 8

an agonist that produces a biological effect without reaching the maximal effect

Question 9

what is an inverse agonist?

Answer 9

an agonist that produces the opposing biological response observed by full agonist

Question 10

what is affinity?

Answer 10

• the ability of a drug molecule to bind to the receptor site
• Ka shows the affinity of the drug

Question 11

what is efficacy?

Answer 11

the ability of a drug to elicit a biological respond from a drug receptor
-measured by eC

Question 12

what determines how ‘tight’ the agonist binds to the receptor?

Answer 12

• the bond type
• weak bonds (reversible binding dissociation): H bonds, ionic bonds, van Der Waal’s
• strong bonds (irreversible binding): covalent bonds

Question 13

why is receptor binding important?

Answer 13

• helps localise functions

- helps see function of the receptors and the biological response associated

Question 14

what does the law of mass action govern?

Answer 14

• the reversible binding of an agonist

- dependent on [reactant] involved

Question 15

what is the law of mass actopm?

Answer 15

• as you increase [A] or [Rfree], [AR] increases

- eventually [AR] fully saturated as all Rfree used up

Question 16

what is Kd?

Answer 16

• Kd is the eqm dissociation constant (reciprocal of Ka) and is also a measure of affinity
• it is where 50% of the max number of receptors are bound
• lower Kd = higher affinity

Question 17

what is the Bmax?

Answer 17

the maximum number of receptors bound to a drug

Question 18

what is potency?

Answer 18

the [drug] needed for effect

-less drug required = more potent the drug

Question 19

explain how buprenorphine is used to treat heroin addicts

Answer 19

• substitution therapy
• buprenorphine has higher affinity to heroin receptors so they displace heroine
• buprenorphine is a partial agonist: still elicits ‘happy’ feeling but not as intense as heroin
• used to reduce withdrawal symptoms
• used to reduce desire for heroin

Question 20

what are competitive antagonists?

Answer 20

drugs that compete w agonists for the binding sites

Question 21

what are non competitive agonists?

Answer 21

drugs that bind to a different site to the agonist to cause functional blockade // or binds to allosteric site of receptor to cause a conformation

Question 22

what is done to overcome the effects of a competitive antagonist and give an example of when this is used?

Answer 22

-increase [A] to overcome effects of Ant

• Used in drug overdose:
• drug overdose causes respiratory depression
• reverse respiratory depression by blocking opioid receptors increasing naloxone (which acts as an opioid antagonist)