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BMS242 PHYSIOLOGY AND PHARMACOLOGY > AGONISTS AND ANTAGONISTS > Flashcards

AGONISTS AND ANTAGONISTS Flashcards

1
Q

DRUGS CAN MAINLY BE CLASSIFIED AS …………………… OR ……………………………

A

AGONIST

ANTAGONIST

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2
Q

OCCUPANCY OF A RECEPTOR BY A DRUG MOLECULE MAY OR MAY NOT RESULT IN ………………………… OF THE RECEPTOR

A

ACTIVATION

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3
Q

WHAT IS OCCUPANCY GOVERNED BY

A

AFFINITY

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4
Q

WHAT IS ACTIVATION GOVERERNED BY

A

EFFICACY

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5
Q

WHAT IS AFFINITY

A

HOW WELL A DRUG BINDS TO A RECEPTRO

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6
Q

WHAT IS EFFICACY

A

HOW WELL A DRUG ACTIVATES A RECEPTOR TO EVOKE A RESPONSE

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7
Q

DEFINE OCCUPANCY

A

PROPORTION OF RECEPTORS OCCUPIED WILL VARY WITH DRUG CONC.
IE
NO. OF RECEPTORS OCCUPIED/TOTAL NO. OF RECEPTORS AVAILABLE

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8
Q

IN THEORY A HIGH OCCUPANCY SHOULD PRODUCE A LARGER RESPONSE. WHY IS THIS NOT ACCURATE

A
  1. THIS DOES NOT WORK FOR ANTAGONISTS AS THEY DO NOT EVOKE A RESPONSE
  2. AGONIST OCCUPANCY AND RESPONSE ARE NOT DIRECT BECAUSE EFFICACY IS THE DETERMINING FACTOR NOT AFFINITY
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9
Q

HOW CAN WE MEASURE OCCUPANCY AND DEDUCE AFFINITY

A

RADIOLIGAND BINDING ASSAY

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10
Q

WHAT IS A RADIOLIGAND BINDING ASSAY

A
  1. SAMPLE THAT CONTAINS A POI
  2. CREATE A RADIOACTIVE VERSION OF THE DRUG WE WANT TO TEST ON THE POI
  3. INCUBATE THE MIXTURE TO REACH EQUILIBRIUM
  4. FILTER AND WASH AWAY NON BOUND (EXCESS) LIGAND
  5. MEASURE THE RADIOACTIVITY LEFT BEHIND (SO WE CAN MEASURE THE RADIOACTIVE DRUG BOUND TO THE RECEPTORS
  6. THIS IS DONE WITH TWO SETS OF TEST TUBES
    1. WILL HAVE SPECIFIC BINDING AND NON
      SPECIFIC BOUND RADIOACTIVE DRUG
    2. WILL HAVE ONLY NON SPECIFIC RADIOACTIVE
      BOUND DRUG
      CAL 1- 2 = SPECIFIC BINDING
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11
Q

HOW MUCH NON SPECIFIC BINDING SHOULD A GOOD DRUG HAVE

A

AS LITTLE AS POSSIBLE

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12
Q

WHAT MAKES FOR A GOOD RADIOLIGAND BINDING EXPERIMENT

A

THE MODIFIED VERSION OF THE DRUG MUST BEHAVE EXACTLY AS BEFORE
THE DRUG MUST BE EXTREMELY PURE
WE MUST PREVENT DEGRADATION OF THE DRUG
WE MUST CONSIDER THE RADIOACTIVE LABEL WE ARE USING

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13
Q

HOW DO YOU PREVENT DEGRADATION OF A DRUG

A

FREE RADICAL SCAVENGER IN DRUG SOLUTION
AVOIDING LIGHT
STORE AT A LOW TEMPERATURE
INCORPORATION OF AN ANTIOXIDANT

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14
Q

WHAT ARE THE ADVANTAGES OF USING TRITIUM IN A RADIOLIGAND BINDING ASSAY

A

DOES NOT CHANGE CHEMICAL NATURE
LONG HALF LIFE
STABLE

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15
Q

WHAT ARE THE DISADVANTAGES OF USING TRITIUM IN A RADIOLIGAND BINDING ASSAY

A

DANGEROUS TO WORK WITH SO SPECIAL LABS NEEDED

DIFFICULT AND EXPENSIVE TO LABEL

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16
Q

WHAT ARE THE ADVANTAGES OF USING I125 IN A RADIOLIGAND BINDING ASSAY

A

SAFER

IODINATION EASY AND CHEAP

17
Q

WHAT ARE THE DISADVANTAGES OF USING I125 IN A RADIOLIGAND BINDING ASSAY

A

DEGRADES MORE QUICKLY
INTERFERES WITH LIGAND MORE
SHORTER HALF LIFE

18
Q

WHAT ARE SOME OF THE PROBLEMS FACED WHEN TRYING TO PRESERVE A POI THAT HAS BEEN PURIFIED IN CENTRIFUGE

A

A CELL MIGHT RELEASE CONTENTS SUCH AS ENZYMES THAT MAY BREAK DOWN THE POI

19
Q

HOW CAN WE PRESERVE THE POI IN A RADIOLIGAND BINDING ASSAY

A

ADDING PROTEASE INHIBITORS
KEEPING THE CELL WHOLE
LOW TEMPERATURES

20
Q

LIGAND BINDING ASSAY DEPEND ON THE MIXTURE REACHING …………………….

A

EQUILIBRIUM

21
Q

IF A LIGAND HAS A LOW AFFINITY THEN WHAT CAN BE SAID ABOUT EQUILIBRIUM

A

IT HAS A FAST BACK RATE AKA SEPARATES FROM THE LIGAND QUICKLY

22
Q

IF A LIGAND IN A BINDING ASSAY HAS A FAST BACK RATE WHAT IMPACT DOES IT HAVE ON THE EXPERIMENT

A

IT IS DIFFICULT TO MEASURE

23
Q

WHAT IS SHOWN IN RADIOLIGAND BINDING CURVES

A

RADIOACTIVITY AGAINST CONCENTRATIONS

PLOTS: TOTAL BOUND, NON SPECIFIC BINDING, SPECIFIC BINDING

24
Q

WHAT IS THE KD

A

A CONSTANT FOR MEASURE OF AFFINITY

25
Q

HOW CAN YOU FIND THE KD

A

FROM THE SCATCHARD EQUATION OR ON A RADIOLIGAND BINDING CURVE AT 50%

26
Q

WHAT IS THE SCATCHARD EQUATION

A

BOUND/FREE = (BMAX-BOUND)/KD

WHERE BMAX IS TOTAL BINDING

27
Q

WHAT IS SHOWN IN A SCATCHARD PLOT

A

BOUND RADIOLIGAND AGAINST B/F
THE X INTERCEPT = BMAX
THE SLOPE = -1/KD

BMS242 PHYSIOLOGY AND PHARMACOLOGY (13 decks)

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