Flashcards in Receptors, agonists and antagonists Deck (18):
Law of mass action
The rate of the reaction is proportional to the concentration of the reactants
Hill Langmuir Equation
pAR or y= [A]/ Ka + [A]
cannot elicit maximum response ( in the absence of spare receptors)
partial agonist at musc receptors
partial agonist at histamine H2 rec
partial agonists at beta rs
prenalterol, full: adrenaline
The EC50 of agonists in tissues vary because of differences in ..
receptor densities and the ability of the receptor to activate the receptor (subtype)= agonist efficacy
and maybe tissue specific factors like the presence of degrading enzymes
measure of affinity : k=1/k-1
measure of efficacy: forward rate(k+2)/ backward rate(K-2)
Antagonists are useful to
block the action of hormones or neurotransmitter, identify receptors and identify enzymes etc involved in signal transduction pathways
The antagonist Kb is ..
independent of the nature of the agonist
NMDA channel can be blocked by ..
Mg2+ or ketamine
Open channel block ..
is a form of non-competitive antagonism, the binding site for antagonist is exposed when the channel opens, has to unblock before it can close
blocks sympathetic and parasympathetic ganglia. In hexamethonium man:
-Symp effects: reduced sweat and secretions, reduced vasoconstriction (vasodilation) of face, hands , lower legs and feet, impotence.
- Parasymp effects: reduced salivary secretions, loss of accomodation, slight tachycardia, impairment of gut movement
is a muscle nicotinic ACh Blocker, decreases amplitude of PSP at NMJ, no AP is induced- competitive, non-depolarising neuromuscular blocker
Suxamethonium is a depolarising, non-competitive blocker
It activates muscle nicotinic Rs, causes prolonged depolarisation, Na channels are inactivated; depolarising blockers are resistant to acetylcholine esterases ( but not to butyrylcholineesterase or plama esterase, therefore breakdown in 2-6 min)
is a short acting choline esterase inhibitor, makes a reversible ionic bond, used in the treatment of myesthenia gravis