John Newport Langley (1852–1925), Paul Ehrlich (1854–1915)
How do drugs produce their effects on the heart or brain? Drugs do not work by uniformly affecting these organs but rather by acting on specific sites called receptors, located in or on the surface of cells. The concept of receptors emerged in the early twentieth century from studies by the English physiologist John Newport Langley and the German microbiologist and chemist Paul Ehrlich. Drugs can produce their effects by acting on many different kinds of receptors, which can, in turn, cause muscle contraction, gland secretion, or mood alteration.
Although a somewhat gross oversimplification, we can envision the interaction of a receptor and drug to be analogous to a lock and key. Just as the correct key fits the keyhole and opens the lock, the “correct” drug binds to a receptor and initiates a response. Further, very similar keys can sometimes open the same lock, and very similar drugs can produce a comparable response. The specific nature of that response differs depending upon where in the body the receptor is located.
Some keys perfectly fit, while others are close enough to fit the keyhole but not close enough to open the lock. An agonist is a drug that perfectly fits the receptor to produce a response. Other drugs called antagonists less perfectly attach to the receptor, and not only fail to produce a response but also prevent the agonist from acting. Receptors were designed in our bodies to interact with natural agonists, such as neurotransmitters or hormones.
There are more than fifty different receptor and sub-receptor types. Drugs that interact with multiple receptor types are likely to produce multiple effects, desirable and undesirable. Over the years, drugs have become increasingly selective in their ability to interact with specific receptors.
SEE ALSO Neurotransmitters (1920), Opioids (1973).
The interaction of a drug and a given receptor is analogous to a lock and key.