Chemical Signaling in the Brain; November 1993; Scientific American Magazine; by Jean-Pierre Changeux; 8 Page(s)

As long ago as 1904, the British scientist T. R. Elliot proposed correctly that neurons (nerve cells) often communicate with one another and with other cell types not electrically but chemically. He suggested that an action potential, or electrical impulse, propagating along an excited neuron triggers the release of chemicals (now called neurotransmitters) from the excited cell. In turn, the liberated chemicals may cause another cell to take in or extrude selected ions. By thus altering the flow of charge across the membrane of this second cell, the neurotransmitters can give rise to a new impulse.

Since then, investigators have identified perhaps 50 neurotransmitters and have learned that a single neuron may secrete several of them. Workers have also struggled to explain just how neurotransmitters, particularly those in the brain, manage to regulate ionic transport, and hence impulse production, in the cells they influence.