Otto Loewi (1873–1961)
When nerves are stimulated, they are able to increase or decrease the activity of their target cells, which include muscles, glands, and the heart. At the turn of the twentieth century, scientific protagonists were at odds explaining how the message was carried from a nerve to a target cell across the synapse—a small but real space between them. This so-called soup versus spark controversy asked, Were messages carried chemically or electrically?
Proof of a chemical messenger came to the German physiologist-pharmacologist Otto Loewi in a dream on the evening before Easter Sunday in 1920. He awoke, scribbled some notes derived from his nocturnal inspiration, and returned to sleep. Upon awakening in the morning, he was unable to decipher his notes. Happily, the same dream recurred the following morning at 3:00 a.m. This time, he rushed to his laboratory at the University of Graz in Austria and, using two beating frogs’ hearts, showed how fluid from a stimulated heart caused another heart to beat more rapidly. Loewi was awarded the 1936 Nobel Prize in Physiology or Medicine—money he used to buy his way out of Austria after Hitler’s 1938 invasion.
HOW NERVES TALK. In addition to Loewi’s first established neurotransmitter, acetylcholine, some of the several dozen other messengers include norepinephrine, dopamine, serotonin, glycine, GABA, and glutamate. These chemicals are synthesized and stored in specific nerve cells and released across a synapse in response to an electrical impulse, binding to a specific receptor on another nerve or target cell. The neurotransmitter-receptor interaction can trigger an increase or decrease in the activity of the target cell, causing contraction or relaxation of a muscle, secretion from a gland, changes in heart rate, and alterations in behavior. The effects of the neurotransmitter are then terminated in several different ways.
Neurotransmitters play a critical role in physiology and behavior, underlying physical and mental disorders and aberrations. Not surprisingly, a wide range of drugs can mimic the effects of naturally occurring neurotransmitters as well as increasing or decreasing the effects of neurotransmitters at their receptor sites.
SEE ALSO Drug Receptors (1905), Neostigmine and Pyridostigmine (1935), Reserpine (1952), Tofranil and Elavil (1957), Monoamine Oxidase Inhibitors (1961), Propranolol (1964), Levodopa (1968), Opioids (1973), Tagamet (1976).
The brain neurotransmitter dopamine is synthesized, stored, and released from a nerve ending, interacting with specific dopamine receptor sites after crossing a synapse.