Physiological agonism and antagonism

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.

Physiological agonists

 * Adrenaline induces platelet aggregation and so does hepatocyte growth factor (HGF) . Thus, they are physiological agonists to each other.

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.