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Medicine: How Nerves Work

2 minute read
TIME

Every muscular function of the human body is triggered by a small electrical current transmitted to the muscles through the nerves. Doctors have long assumed that a chemical reaction at the synapses (the junctions between nerves) causes the impulses to flow through the nerves until—through junction after junction—they reach the muscles. But the chemistry of impulse transmission along the nerve fibers was not known. Last week Colum bia University announced that Dr. David Nachmansohn and his colleagues in the university’s Department of Neurology had found new evidence to support his 20-year-old theory of the biochemical reaction that lets a nerve carry a current, then shut it off.

By isolating a “receptor” protein, the Columbia biochemists proved that the same reaction that takes place at the synapse is repeated all along the length of the nerve. When a nerve is stimulated, a chemical called acetylcholine is released within the nerve. It combines with the receptor protein, causing an interchange of sodium and potassium ions. The ions in turn trigger release of more acetylcholine a bit farther along the line, letting the current advance. To turn off the signal, an enzyme, cholinesterase, is released that instantly destroys the acetylcholine in the nerve.

Identifying and relating the chemicals involved in this process has been Dr. Nachmansohn’s life work. Four years ago, while studying cholinesterase, he stumbled on a chemical, nicknamed PAM, which proved an effective antidote to deadly nerve gases. Now his explanation of how nerves work offers insight into yet another obscure matter: how nerves are deadened by anesthesia. The discovery that such anesthetics as procaine and the Indian poison curare combine easily with the receptor protein, blocking the biochemical reaction, could lead to better anesthetics and more efficient drugs for treating disorders of the human nervous system. “One of the basic functions of human life is coming closer to being understood,” said Dr. Nachmansohn.

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