Main Body

2. Introduction to Drug-Receptor Interactions and Pharmacodynamics

Receptors: protein molecules including enzymes, transporters and ion channels where a ligand (specific endogenous neurotransmitter/hormone or an external pharmacological agent (drug)) binds to, resulting in a cellular response.

  • Unique Exception: Orphan Receptors are receptors for which the ligand remains unknown.
  • Reminder: Ligand is an ion or molecule that forms a complex with a biomolecule to serve a specific biological purpose

Examples of Endogenous Ligands:

    • Neurotransmitters[NT]: chemical messengers signaling across a synaptic cleft
      • Acetylcholine [Ach]
      • Epinephrine [EPI]
      • Norepinephrine [NE]
    • Hormones (peptide): secreted from neuroendocrine cells into the blood to signal at distant cells and tissues.
      • Aldosterone
      • Insulin
      • Nerve growth factor [NGF]
      • Thyroid hormone [TH]
  • Insulin is synthesized and released by pancreatic beta cells. It is transported through the blood to a variety of cells to stimulate those cells to express glucose transporters allowing those cells to bring glucose into the cell for energy utilization.

DRUG: A chemical agent that selectively interacts with specific target molecules (i.e. receptors) to alter their specific physiological functions.

  • Agonist: drug that activates receptors to result in either stimulation or inhibition of the function of various types of cells and organs.
  • Antagonist: drug that prevents receptor activation by agonists.

Drug-Receptor Binding: drugs bind to their respective receptor in a variety of ways depending on their characteristics.

  • Ionic interaction: cation & anion
  • Hydrogen bonding
  • Lipophilic interaction
  • Covalent bond: irreversible


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Principles of Pharmacology - Study Guide Copyright © by Edited by Dr. Esam El-Fakahany and Becky Merkey, MEd is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.