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38 terms

U2L08 Responses to antagonists

Lecture 8 of BMED2802 (Robin Allan, 2009) at the University of Sydney.
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competitive (reversible), competitive (irreversible) and non-competitive
What are the three types of antagonist?
affinity
Occupation is governed by what property of the receptor-drug interaction?
efficacy
Activation is governed by what property of the receptor-drug interaction?
atropa belladonna
What plant is atropine derived from?
selective muscarinic antagonist
What is atropine?
10^-8 mol/L
At approximately what concentration is atropine active?
pupils dilate, dry mouth, hallucinations
What are the effects of atropine?
dose ratio
What does DR stand for in the antagonist calculations?
how much more is needed in presence of antagonist to get same response
What does DR represent?
log(DR - 1) = log XB - log KB
What is the equation for the Schild plot?
1
If competitive antagonism, slope of the Schild plot will be...
KB
If competitive antagonism, what will the x-intercept of the Schild plot be?
log xB
What is on the x-axis of the Schild plot?
log(DR - 1)
What is on the y-axis of the Schild plot?
-log xB when DR = 2, or x intercept on Schild plot
What equation is used to calculate pA2?
shifts to right
How does a competitive antagonist change the dose-response curve for an agonist?
it doesn't
How does a competitive antagonist change the maximum response?
define antagonist drug, receptor classification
What purposes is the pA2 widely used for?
independent of it
What relationship does the pA2 have to the agonist?
antagonist and receptor
What does the pA2 depend on?
pA2
The negative logarithm to base 10 of the molar concentration to reduce the effect of a dose of agonist to that of half the dose
agonists and antagonists
Partial agonists have properties of both...
atropine
An antagonist of muscarinic cholinergic receptors
hexamethonium, decamethonium, tubocurarine
3 antagonists of nicotinic cholinergic receptors
ganglionic
Which nicotinic cholinergic receptors does hexamethonium act on?
neuromuscular junction
Which nicotinic cholinergic receptors do decamethonium and tubocurarine act on?
depolarising block
What is unusual about the action of decamethonium?
mepyramine
An antagonist of histamine H1 receptors
propranolol
An antagonist of β-adrenoceptors
receptor reserve
The concept that the pool of receptors is larger than needed for full response
Scatchard plot
What plot is used to calculate the total number of binding sites?
Bmax
The total number of binding sites is known as...
[bound]
What is on the x-axis of the Scatchard plot?
[bound]/[free]
What is on the y-axis of the Scatchard plot?
-1/KD
What does the slope of the Scatchard plot represent?
Bmax (total binding sites)
What does the x-intercept of the Scatchard plot represent?
radioactive labelling
How do you measure extremely low concentrations as seen in the Scatchard plot?
elicit a response
Antagonists, by themselves, do not...