Drug Action Vocab

Ligand-gated ion channel

Interaction of the chemical signal with an extracellular receptor binding site that causes the opening or closing of an ion channel pore in another part of the same molecule

Enzyme-linked receptor

Enzyme whose catalytic activity is regulated by the binding of an extracellular signal

G-protein coupled receptor (GPCR)

Regulates intracellular reactions by an indirect mechanism involving an intermediate transducing molecules, called GTP-binding proteins

Intracellular receptor

Receptor in the cell that is activated by a cell-permeable and/or lipophilic signaling molecule; often alters gene expression

Drug target

Molecule or structure that a drug interacts with the alter a biological process

Dissociation constant (K_D)

Describes the affinity between a ligand and its receptor; the smaller the value, the stronger the binding

B_max

Total number of receptors present in a cell or tissue

ED₅₀

Dose required to produce 50% of the desired maximum response

Potency

Measurement of activity of a drug in a biological system; dose of a drug required to produce a particular effect of a given intensity

Efficacy

Measurement of how well an agent/drug elicits a response in the biological system

Agonist

Drug that binds to physiological receptors and mimics the regulatory effects of the endogenous signaling compounds

Full agonist

Agents that are just as efficacious as the endogenous ligand at a particular receptor site; elicits maximum response

Partial agonist

Agents that are only partly as efficacious as the endogenous ligand at a particular receptor site; elicits less than maximum response

Inverse agonist

Agent that binds to a receptor like an agonist but elicits a response that is opposite from the endogenous ligand at a particular receptor site; elicits a below-baseline response