Word: braine
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Dates: during 1990-1999
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...abrupt change also reflects a deeper truth about serotonin: despite years of study and impressive breakthroughs, researchers are only beginning to understand the chemical's complex role in the functioning of the body and brain--and how doctors can make adjustments when serotonin levels go out of balance. So far, the tools used to manipulate serotonin in the human brain are more like pharmacological machetes than they are like scalpels--crudely effective but capable of doing plenty of collateral damage. Says Barry Jacobs, a neuroscientist at Princeton University: "We just don't know enough about how the brain works...
Still, there is plenty that researchers do understand. At the most basic level, they have been aware for more than two decades that without serotonin, dopamine, norepinephrine and the hundreds of other known neurotransmitters, the brain could not process information or send out instructions to run the rest of the body. That is because neurons, or nerve cells, do not actually touch one another; they are separated by gaps known as synapses. When the electrical impulses that carry information through the nervous system reach the end of a neuron, they have nowhere to go. The circuit is broken...
...small subset of these brain chemicals, especially serotonin, evidently serves an entirely different purpose. As Steven Hyman, director of the National Institute of Mental Health, describes it, "These neurotransmitters modulate raw information and give it its emotional tone." Northwestern University psychiatrist James Stockard puts it more poetically: "A person's mood is like a symphony, and serotonin is like the conductor's baton." Other neurotransmitters help us know our stomachs are full; serotonin tells us whether we feel satisfied. Other chemicals help us perceive the water level in a glass; serotonin helps us decide whether we will think...
With such a broad neurological portfolio, it is no wonder these mood-changing brain chemicals have been implicated in so many mental disorders. And it is not surprising that serotonin appears to be especially important--the first among equals, in a sense. The nerve cells that specialize in serotonin production originate in the raphe nuclei, in a region right atop the spine that nimh's Hyman calls "the deep basement of the brain." From there, these neurons extend vinelike projections called axons up through the brain and down into the spinal column. The axons form a sort of neurological interstate...
...depending on a variety of factors. To begin with, each neurotransmitter can latch onto more than one kind of receptor. As many as 15 distinct receptors have been identified for serotonin alone. And since a given nerve cell may have more or fewer receptors, depending on where in the brain it is located, a jolt of a particular neurotransmitter can generate electrical signals of widely varying strengths. Small wonder, therefore, that serotonin can affect everything from satiety to depression...