| receptors, adrenergic | Cell-surface proteins that bind epinephrine and/or norepinephrine with high affinity and trigger intracellular changes. The two major classes of adrenergic receptors, alpha and beta, were originally discriminated based on their cellular actions but now are distinguished by their relative affinity for characteristic synthetic ligands. Adrenergic receptors may also be classified according to the subtypes of g-proteins with which they bind; this scheme does not respect the alpha-beta distinction. (12 Dec 1998) |
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| receptors, adrenergic, alpha | One of the two major pharmacological subdivisions of adrenergic receptors. The alpha-beta distinction was originally based on cellular effects of receptor activation but now relies on the relative affinities for certain synthetic ligands. Alpha-adrenergic receptors are further subdivided into several subclasses based on studies of endogenous and cloned receptors. (12 Dec 1998) |
| receptors, adrenergic, alpha-1 | A subclass of alpha-adrenergic receptors (receptors, adrenergic, alpha). Alpha-1 adrenergic receptors can be pharmacologically discriminated, e.g., by their high affinity for the agonist phenylephrine and the antagonist prazosin. They are widespread, with clinically important concentrations in the liver, the heart, vascular, intestinal, and genitourinary smooth muscle, and the central and peripheral nervous systems. (12 Dec 1998) |
| receptors, adrenergic, alpha-2 | A subclass of alpha-adrenergic receptors (receptors, adrenergic, alpha). Alpha-2 adrenergic receptors can be pharmacologically discriminated, e.g., by their high affinity for the agonist clonidine and the antagonist yohimbine. They are found on pancreatic beta cells, platelets, and vascular smooth muscle, as well as both pre- and postsynaptically in the central and peripheral nervous systems. (12 Dec 1998) |
| receptors, adrenergic, beta | One of the two major pharmacologically defined classes of adrenergic receptors. The alpha-beta distinction was originally based on the cellular effects of receptor activation but now relies on the relative affinities for characteristic synthetic ligands. Beta adrenergic receptors are further subdivided based on information from endogenous and cloned receptors. (12 Dec 1998) |
| receptors, adrenergic, beta-1 | A subclass of beta-adrenergic receptors (receptors, adrenergic, beta). Beta-1 adrenergic receptors are equally sensitive to epinephrine and norepinephrine and bind the agonist dobutamine and the antagonist metoprolol with high affinity. They are found in the heart, juxtaglomerular cells, and in the central and peripheral nervous systems. (12 Dec 1998) |
| receptors, adrenergic, beta-2 | A subclass of beta-adrenergic receptors (receptors, adrenergic, beta). Beta-2 adrenergic receptors are more sensitive to epinephrine than to norepinephrine and have a high affinity for the agonist terbutaline. They are widespread, with clinically important roles in skeletal muscle, liver, and vascular, bronchial, gastrointestinal, and genitourinary smooth muscle. (12 Dec 1998) |
| agent | <pharmacology> Any power, principle or substance capable of producing an effect, whether physical, chemical or biological. Origin: L. Agens = acting (18 Nov 1997) |
| agent, antihypertensive | As the name suggests, a drug aimed at reducing high blood pressure (hypertension). (12 Dec 1998) |
| agent, anti-infective | Something capable of acting against infection, by inhibiting the spread of an infectious agent or by killing the infectious agent outright. (12 Dec 1998) |
| Agent Orange | An herbicide and defoliant, consisting of (2,4,5-trichlorophenoxy)acetic acid, (2,4-dichlorophenoxy)acetic acid, and dioxin, that was widely used in the Vietnam War; it has been shown to possess residual post-exposure carcinogenic and teratogenic properties in humans. (05 Mar 2000) |
| agent, tocolytic | A medication that can inhibit labour, slow down or halt the contractions of the uterus. Tocolytic agents are widely used today to treat premature labour and permit pregnancy to procede and so let the foetus gain in size and maturity before being born. (12 Dec 1998) |
| alkylating agent | <oncology, pharmacology> A reagent that places an alkyl group, for example propyl in place of a nucleophilic group in a molecule. Alkylating reagents include a number of cytotoxic drugs some of which react fairly specifically with N7 of the purine ring and lead to depurination of DNA, for example the agent ethyl ethanesulphonic acid and thus to mutagenesis. The drugs interaction with DNAand prevents the division of the cells. Examples of drugs include: busulphan, chlorambucil, cyclophosphamide, melphalan. (29 Sep 1997) |
| antianxiety agent | A functional category of drugs useful in the treatment of anxiety and able to reduce anxiety at doses which do not cause excessive sedation (e.g., diazepam). Synonym: anxiolytic, minor tranquilliser. (05 Mar 2000) |
| antidiabetic agent | A substance that helps a person with diabetes control the level of glucose (sugar) in the blood so that the body works as it should. See: insulin. (09 Oct 1997) |