Physiological agonism and antagonism is the mechanism of substances to induce the same ultimate effects in the body as other substances, as if they were receptor agonists or antagonists, but without binding to the same receptor. Antagonists will block the binding of an agonist at a receptor molecule, inhibiting the signal produced by a receptor-agonist coupling. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ...

Examples

Physiological agonists

• Adrenaline induces platelet aggregation and so does hepatocyte growth factor (HGF)^[1]. Thus, they are physiological agonists to each other.

Epinephrine (INN) or adrenaline (BAN) is a hormone and a neurotransmitter. ... Hepatocyte growth factor is a cytokine. ...

Physiological antagonists

• There are several physiological antagonists that have antihistaminergic action. For instance, adrenaline raises arterial pressure through vasoconstriction mediated by β-adrenergic receptor activation, in contrast to the histamine effect of lowering arterial pressure. However, only such substances that bind and block the histamine receptor are true antihistamines.

An antihistamine is a drug which serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions, through action at the histamine receptor. ... Epinephrine (INN) or adrenaline (BAN) is a hormone and a neurotransmitter. ... Epinephrine Norepinephrine The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. ... This article or section does not cite any references or sources. ... The histamine receptors are a class of G-protein coupled receptors with histamine as their endogenous ligand. ... An H1 antihistamine is a histamine antagonist which serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions, through action at the H1 receptor. ...

References

1. ^ doi:10.1016/j.febslet.2005.06.072 Met identification on human platelets: Role of hepatocyte growth factor in the modulation of platelet activation Copyright © 2005 Published by Elsevier B.V. Edited by Veli-Pekka Lehto. Daniela Pietrapiana, Marilena Sala, Maria Prat1 and Fabiola Sinigaglia, 1, Department of Medical Science, University “A. Avogadro”, Via Solaroli, 17, Novara 28100, Italy Received 4 May 2005; revised 15 June 2005; accepted 21 June 2005. Available online 19 July 2005.