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Related Concept Videos

Combined Effects of Drugs: Antagonism01:30

Combined Effects of Drugs: Antagonism

The combined effects of drugs can result in various interactions, of which an important type is antagonism. Antagonism is a mechanism where one drug inhibits or counteracts the effects of another drug. Antagonism can occur through various means, including receptor binding, allosteric modulation, functional interaction, chemical reactions, and pharmacokinetic processes.
The most common type is receptor antagonism, where one drug acts as an antagonist to block the effects of another drug by...
Agonism and Antagonism: Quantification01:14

Agonism and Antagonism: Quantification

When drugs are administered, they can elicit either an agonist or antagonist effect on the body. Agonism occurs when a drug activates a specific receptor, triggering a biological response. On the other hand, antagonism happens when a drug binds to the same receptors but blocks their activation, thereby preventing a biological response.
To quantify these effects, researchers use a dose-response curve, which provides valuable information about the potency and efficacy of a drug. Potency refers to...
Drug-Receptor Interaction: Agonist01:25

Drug-Receptor Interaction: Agonist

Agonists are drugs that interact with specific receptors in the body to produce a biological response. When an agonist binds to a receptor, it activates or enhances the receptor's function, leading to physiological effects. The interaction between agonist drugs and receptors is crucial for their therapeutic action in various medical treatments.
Agonists can bind to receptors in different ways. Some agonists bind directly to the receptor's active site, mimicking the endogenous ligand's action.
Drug-Receptor Interaction: Antagonist01:28

Drug-Receptor Interaction: Antagonist

An antagonist is a drug that binds strongly to a receptor without activating it. An antagonist prevents other molecules, such as neurotransmitters or hormones, from binding to the receptor and triggering a cellular response. Such interaction effectively hinders the normal physiological processes mediated by the receptor, resulting in various pharmacological effects depending on the specific receptor targeted.
Antagonists can be classified as competitive or noncompetitive based on their...
Drug-Receptor Interactions01:29

Drug-Receptor Interactions

Drug-receptor interaction describes the binding of receptors by drugs, but not all drug-receptor interactions result in activation and tissue response. For instance, the binding of agonists activates the receptor to generate a cellular reaction, while antagonists bind to receptors without causing their activation.
Several parameters, such as the drug's affinity for its receptor and its efficacy, which is its ability to activate the receptor, determine the drug's effect on the tissue.
Principles of Drug Action01:24

Principles of Drug Action

Drugs are chemical substances that modify biological responses by interacting with macromolecular targets such as receptors, ion channels, transporters, and enzymes. Pharmacodynamics describes the course of action of drugs leading to the physiological effect at a specific site in the body.
Drugs can be agonists or antagonists. Like the endogenous ligands, agonists always bind and activate the target to produce a cellular response. Agonist binding induces a conformational change which in turn...

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Related Experiment Video

Updated: Jun 18, 2026

Methods for the Discovery of Novel Compounds Modulating a Gamma-Aminobutyric Acid Receptor Type A Neurotransmission
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Published on: August 16, 2018

Drug effects: agonistic and antagonistic processes.

Magne Arve Flaten1

  • 1Department of Psychology, University of Tromsø, Norway. magne.flaten@uit.no

Scandinavian Journal of Psychology
|November 26, 2009
PubMed
Summary

Drug tolerance and placebo effects can be influenced by conditioning processes. Expectations, objectively measured through physiological and behavioral methods, significantly impact drug responses, demonstrating a graded effect on symptoms.

Area of Science:

  • Psychopharmacology
  • Neuroscience
  • Behavioral Science

Background:

  • Drug tolerance can be accelerated by conditioning.
  • Placebo effects are the opposite of tolerance and can be objectively measured.
  • Expectations play a crucial role in modulating drug responses.

Purpose of the Study:

  • To investigate the role of conditioning in drug tolerance and placebo effects.
  • To objectively record placebo effects using physiological and behavioral measures.
  • To understand how expectations influence drug efficacy and antagonism.

Main Methods:

  • Electromyography (EMG)
  • Skin conductance responses (SCR)
  • Event-related potentials (ERPs)
  • Behavioral assessments

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Last Updated: Jun 18, 2026

Methods for the Discovery of Novel Compounds Modulating a Gamma-Aminobutyric Acid Receptor Type A Neurotransmission
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Published on: August 16, 2018

Quantifying Agonist Activity at G Protein-coupled Receptors
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Assessment of Social Interaction Behaviors
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  • Subjective reports

    • Main Results:

    • Conditioning processes can accelerate drug tolerance.
    • Placebo effects were objectively recorded using physiological and behavioral methods.
    • Expectations can enhance drug effects or reverse them (antagonistic expectations).
    • Placebo effects are strongest when reinforced by active drug administration.
    • Expectations demonstrate graded effects on symptom severity.

    Conclusions:

    • Conditioning plays a significant role in drug tolerance and placebo effects.
    • Objective physiological and behavioral measures can quantify placebo responses.
    • Expectations are a powerful modulator of drug action, with graded influence on symptoms.
    • Classical conditioning in drug use requires careful consideration due to its complex nature.