Pharmacology
Pharmacodynamics
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Get accessDrug effects mediated by binding to a cellular membrane receptor or by inhibiting specific biochemical enzymes
Receptors are typically cell surface proteins that bind ligands by a lock-and-key principle and initiate transduction
Ion channels: receptor may be linked to an ion channel which only opens when a ligand is bound
ACh and glutamate increase sodium and potassium permeability resulting in depolarisation
Second messengers: receptor binding alters intracellular functions via secondary messenger systems, often a protein kinase and phosphorylation of membrane proteins
Adenyl cyclase is activated and synthesises cAMP from ATP leading to calcium ion influx downstream
Protein synthesis: some drugs pass across cell membranes and bind to cytoplasmic receptors or directly to the nucleus to alter protein production
- Eg. steroids
Affinity between ligands and its receptors is quantified by the amount of ligand required to achieve half-maximal binding (EC50)
- Partial agonist
- Both agonist and antagonist qualities
- At high concentrations, exerts antagonist activity by blocking true agonists