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18 Cards in this Set
- Front
- Back
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Targets for drugs...
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Ion Channels
Enzymes Receptors Transporters (energy-dependent/independent) Nucleic Acids Misc. |
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Toxin affecting Na+ channels.
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Tetrodotoxin (TTX):
- Contains +ve Guanidino Group which binds to COO- on Glu residues of channel. - Blocks Channel - LD50 = 5 micrograms per Kg. |
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Which transporter-targeting drug is used to treat depression? What does it target?
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Fluoxetine
- Inhibits Serotonin transporter in the brain. - Increase in Serotonin concentrations in synapse, so increased binding. - Happy feelings. |
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How does Cocaine cause Euphoric effects?
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Blocks NA-1 Uptake transporter
- Increase in Synaptic NA, Dopamine, Serotonin. - So creates euphoria. |
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Receptor Superfamilies
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Ionotropic - linked to ion channels.
Metabotropic - GPCRs Tyrosine Kinases DNA-Linked |
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Example of ionotropic receptor
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nAChr - Pentameric,
2 x Alpha, 1 x Beta, Gamma and Delta sub-units. 2 x ACh must bind to the N-terminus of the alpha sub-unit to open channel. |
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Pathways which are linked to GPCRs
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Adenylate Cyclase - cAMP
Phospholipase C - IP3, DAG Guanyl Cyclase - Sodium nitroprusside |
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What is Kd?
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Concentration of drug at which 50% occupancy is reached.
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What is EC50?
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Concentration of drug at which 50% of the maximum response is elicited.
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Binding is....
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Saturable.
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Histamine receptors were discovered to have sub-types. What are these sub-types and how are they useful in clinical practice?
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H1 - Smooth muscle contraction.
H2 - Gastric Acid secretion. H1 antagonists -> Anti-allergy. H2 antagonists -> Anti-ulcer. |
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Affinity
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How well the receptor will bind the drug molecule.
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Efficacy
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How effective the drug is at activating the receptor once bound [DR]*.
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Is Efficacy related to Occupancy? Explain.
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No.
EC50 does not equal KD. Not a linear relationship. Lower drug concentrations than Kd may elicit 50% of maximum response. This is due to Amplification of signals. |
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On a graph, what does the relationship between Kd and EC50 tell you?
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EC50 will be closer to KD when the efficacy is low.
They will be farther apart when efficacy is high. |
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Receptor reserve.
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The number of free receptors once a drug has produced maximal response.
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When would a drug produce a HIGH receptor reserve?
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When it has a high efficacy. Lower [D] will be recquired, so more [R] present.
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Importance of receptor reserve.
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Safety - too high [D], toxic.
Economy - don't waste money Low efficacy drugs may have a place in therapeutics. |
