Endorphins

The structure of an endorphin 
molecule. Image from Snyder, 
1996. Used with permission 
from W.H. Freeman and Company.

 Endorphins are a group of ten neurotransmitters that activate opiate receptors.  Endorphins are composed of chains of amino acids between five and several dozen members long (Hollt, 1983).  Since the discovery of the endorphins in 1975, scientists have hypothesized that these neurotransmitters are released into synapses when the body encounters stress.  After a physical injury, endorphins activate opiate receptors and produce an analgesic effect, alleviating severe pain.  During times of emotional stress, endorphins are released in the limbic system of the brain and produce a euphoria that lessens anxiety and melancholy (Rang et al., 1995). 

Recently, scienctists have hypothesized that the release of endorphins is the neurochemical cause for the feeling of pleasure.  For example, a marathon runner's "high," which has been compared to the "rush" following opioid use, is the product of endorphin release (Hawkes, 1992).  

Unlike opioids, the body's endorphins are not addicting.  When endorphins are not activating receptors, no withdrawal symptoms are felt.  Enzymes break down endorphins as soon as they act at receptors, so they are never in contact with receptors long enough to form tolerance or dependency.  Researchers have been unable to produce drugs that are rapidly  broken down by the body's enzymes, but still produce strong analgesia (Snyder, 1996). 


    Main Page   History 1    History 2    Ligands & Receptors   Opiate Receptors    Analgesia 1    Analgesia 2   Euphoria    Tolerance & Dependency    Common Opioids    Current Research    Acknowledgments   Literature Cited

Animal Physiology HOT TOPICS
   This site was created during the fall semester of 1999 by Wes Self, a student at 
  Davidson College, as part of an assignment in Biology 312 (Animal Physiology). 

  Questions, comments and suggestions are appreciated at weself@davidson.edu