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药理学术语

Pharmacological Glossary

Definitions of commonly used pharmacological terms

Term

Description

Agonist

A drug that binds to and activates a receptor. Can   be full, partial or inverse. A full agonist has   high efficacy, producing a full response while occupying a relatively low   proportion of receptors. A partial agonist has lower efficacy than a   full agonist. It produces sub-maximal activation even when occupying the   total receptor population, therefore cannot produce the maximal response,   irrespective of the concentration applied. An inverse agonist produces   an effect opposite to that of an agonist, yet binds to the same receptor   binding-site as an agonist.

Allosteric Modulator

A drug that binds to a receptor at a site distinct   from the active site. Induces a conformational change in the receptor, which   alters the affinity of the receptor for the endogenous ligand. Positive   allosteric modulators increase the affinity, whilst negative allosteric   modulators decrease the affinity.

Antagonist

A drug that attenuates the effect of an agonist. Can   be competitive or non-competitive, each of which can be reversible   or irreversible. A competitive antagonist binds to the same   site as the agonist but does not activate it, thus blocks the agonist’s   action. A non-competitive antagonist binds to an allosteric   (non-agonist) site on the receptor to prevent activation of the receptor. A reversible   antagonist binds non-covalently to the receptor, therefore can be “washed   out”. An irreversible antagonist binds covalently to the receptor and cannot   be displaced by either competing ligands or washing.

Bmax

The maximum amount of drug or radioligand, usually   expressed as picomoles (pM) per mg protein, which can bind specifically to   the receptors in a membrane preparation. Can be used to measure the density   of the receptor site in a particular preparation.

Cheng-Prusoff Equation

Used to determine the Ki value from an IC50   value measured in a competition radioligand binding assay:
 
  Where [L] is the concentration of free radioligand, and Kd is the   dissociation constant of the radioligand for the receptor.

Desensitization

A reduction in response to an agonist while it is   continuously present at the receptor, or progressive decrease in response   upon repeated exposure to an agonist.

EC50

The molar concentration of an agonist that produces   50% of the maximum possible response for that agonist.

ED50

In vitro or in vivo dose of drug that produces 50% of   its maximum response or effect.

Efficacy

Describes the way that agonists vary in the response   they produce when they occupy the same number of receptors。 High efficacy   agonists produce their maximal response while occupying a relatively low   proportion of the total receptor population。 Lower efficacy agonists do not   activate receptors to the same degree and may not be able to produce the   maximal response。

Ex vivo

Taking place outside a living organism.

Half-life

Half-life (t?) is an important pharmacokinetic   measurement. The metabolic half-life of a drug in vivo is the time   taken for its concentration in plasma to decline to half its original level.   Half-life refers to the duration of action of a drug and depends upon how   quickly the drug is eliminated from the plasma. The clearance and   distribution of a drug from the plasma are therefore important parameters for   the determination of its half-life.

i.a.

Intra-arterial route of drug administration

IC50

In a functional assay, the molar concentration of an   agonist or antagonist which produces 50% of its maximum possible inhibition.   In a radioligand binding assay, the molar concentration of competing ligand   which reduces the specific binding of a radioligand by 50%.

i.c.

Intracerebral route of drug administration.

i.c.v.

Intracerebroventricular route of drug administration.  

ID50

In vitro or in vivo dose of a drug that causes 50% of   the maximum possible inhibition for that drug.

i.d.

Intradermal route of drug administration.

i.g.

Intragastric route of administration.

i。m。

Intramuscular route of drug administration.

In vitro

Taking place in a test-tube, culture dish or   elsewhere outside a living organism.

In vivo

Taking place in a living organism.

i.p.

Intraperitoneal route of drug administration.

i.t.

Intrathecal route of drug administration.

i.v.

Intravenous route of drug administration.

KB

The equilibrium dissociation constant for a   competitive antagonist: the molar concentration that would occupy 50% of the   receptors at equilibrium。

Kd

The dissociation constant for a radiolabeled drug   determined by saturation analysis. It is the molar concentration of   radioligand which, at equilibrium, occupies 50% of the receptors.

Ki

The inhibition constant for a ligand, which denotes   the affinity of the ligand for a receptor. Measured using a radioligand   competition binding assay, it is the molar concentration of the competing   ligand that would occupy 50% of the receptors if no radioligand was present.   It is calculated from the IC50 value using the.

Non-Specific Binding

The proportion of radioligand that is not displaced   by other competitive ligands specific for the receptor。 It can be binding to   other receptors or proteins, partitioning into lipids or other things。

pA2

Measure of the potency of an antagonist. It is the   negative logarithm of the molar concentration of an antagonist that would   produce a 2-fold shift in the concentration response curve for an agonist.

pD2

The negative logarithm of the EC50 or IC50   value.

pEC50

The negative logarithm of the EC50 value.  

pIC50

The negative logarithm of the IC50 value.  

pKB

The negative logarithm of the KB value.

pKd

The negative logarithm of the Kd value.

pKi

The negative logarithm of the Ki value.

p。o。

Oral (by mouth) route of drug administration。

Potency

A measure of the concentrations of a drug at which   it is effective。

s。c。

Subcutaneous route of drug administration

Specific Binding

The proportion of radioligand that can be displaced   by competitive ligands specific for the receptor。

Silent Antagonist

A drug that attenuates the effects of agonists or   inverse agonists, producing a functional reduction in signal transduction.   Affects only ligand-dependent receptor activation and displays no intrinsic   activity itself. Also known as a neutral antagonist.

Systemic

In the periphery of the body (not in the central   nervous system.

t?

Biological half-life。

 


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