Plain-language explanations of how drugs act on receptors. Educational information only, not medical advice.
A plain-language introduction to receptor agonists: what receptors are, how natural messengers and medicines switch them on, and why affinity and efficacy matter.
How agonists activate receptors while antagonists block them, the difference between competitive and non-competitive antagonism, and real examples such as naloxone and beta-blockers.
A clear explanation of dose-response curves in pharmacology: what EC50 and Emax mean, how potency differs from efficacy, and how quantal curves lead to the therapeutic index.
How intrinsic efficacy determines a drug's maximal response.
How some drugs reduce receptor activity below its resting level.
What receptor selectivity means in pharmacology, why it is relative rather than absolute, and how subtypes, tissue location and delivery route shape a drug's effects and side effects.
Why receptors become less responsive with repeated agonist exposure.
What biased agonism (functional selectivity) means, how G protein and arrestin pathways differ, why it attracted interest for opioid research, and why its clinical value is still debated.
How drugs that bind a second site change the effect of agonists.
An introduction to G protein-coupled receptors (GPCRs): their seven-helix structure, the Gs, Gi and Gq signalling pathways, arrestins, and familiar medicines that act on them.
How ligand-gated ion channels such as nicotinic, GABA-A, glycine, 5-HT3 and glutamate receptors work, how agonists open them within milliseconds, and how modulators differ from agonists.
How nuclear receptors work as ligand-activated transcription factors, and how agonists such as corticosteroids, thyroid hormone, PPAR agonists and vitamin D analogues change gene expression.
A guide to adrenergic receptor agonists: how alpha-1, alpha-2, beta-1, beta-2 and beta-3 receptors differ, and familiar examples from decongestants and eye drops to bladder medicines.
How beta-2 agonists relax the airways and how short- and long-acting types differ.
How cholinergic agonists act on muscarinic and nicotinic acetylcholine receptors, examples such as pilocarpine and bethanechol, how they differ from cholinesterase inhibitors, and key cautions.
How dopamine receptor agonists work: D1-like and D2-like receptors, why the class is used in Parkinson's disease, restless legs syndrome and high prolactin, and the main known cautions.
An overview of serotonin (5-HT) receptor families and the agonists that act on them: triptans and ditans for migraine, 5-HT1A partial agonists, and safety lessons such as the 5-HT2B receptor.
How opioid receptor agonists relieve pain, and why their risks are substantial.
How GLP-1 receptor agonists work: the natural incretin hormone GLP-1, why the native hormone is short-lived, how drug versions were modified, and the main effects and cautions.
How the idea of drug receptors developed: Langley's receptive substance, Ehrlich's chemoreceptors, Clark's occupancy theory, efficacy, adrenoceptor subtypes and the structural era.