It is almost as if people were programmed to become [TEXT OMITTED FROM SOURCE]

Through evolution, this pleasure center has insured its own survival. As primitive animals developed in a hostile environment, those that derived the most pleasure from chasing, capturing and ultimately eating food were the most likely to thrive. Those that derived the most pleasure from pursuing mates and engaging in sex were the most likely to reproduce.

Other things being equal, sensitivity to pleasure was an evolutionary advantage, scientists believe. And those pleasure genes spread through subsequent generations.

Now, millions of years later, the human pleasure center is highly developed, extraordinarily sensitive and dangerously vulnerable. This is the genesis of addiction.

"So much of what we do, so many of our values are driven by the pleasure principle, and people don't want to look at that," said Dr. Charles Dackis of Fair Oaks Hospital in Summit, N.J., one of the nation's leading cocaine addiction treatment centers. "We're programmed to procreate, eat food, drink fluids, and the pleasure is what gets organisms to do that. It's in the hardware. Then you get cocaine, which tricks the brain into thinking it's doing something for survival."

One former cocaine addict described the sensation this way: "You'd be driving down the road, and all you can see in front of you is cooking up the freebase. I could actually see it."

This 28-year-old Washington account executive and other former drug users agreed to be interviewed on the condition that their identities not be revealed.

For several years, while he used cocaine hydrochloride in its white granular form, chopping it to a powder and inhaling, or snorting, it through a rolled-up $20 bill, his habit was largely under control. He would go for weeks or months at a time without the drug and without a craving.

But when he began to use freebase -- a modified form of cocaine smoked through a glass pipe -- and to inject a liquid form of the drug, the craving became impossible to resist.

"My body would get hot. I'd be shaking. My stomach would feel funny," he recalled recently. "There's nothing that would have gotten in my way."

He often stayed home from work, his social life was failing, and he was deeply in debt. "I did not pay any utility bills," he said. "I did not pay any rent. I wore the same pair of shoes for two years." On occasion, he would steal money from his dealer's house, then return to buy cocaine.

Seven months ago, after missing work for two weeks in a row, he joined a Cocaine Anonymous group in suburban Virginia and has not used the drug since.

His progression from occasional social use of cocaine powder to an intense addiction to freebase cocaine reflects the evolution of the drug in the past decade.

The drug was once confined to the rich, particularly people in show business. "You know who cared? The studio owners," said Dr. Mark Gold, founder of a national cocaine hotline. "We even had a counselor at the Beverly Hills Hotel," he said, because there were no treatment centers.

As supplies increased, cocaine became available to people with less money, and now even the poor can often afford it. What authorities are worried about, and are beginning to see, is growing use of these more potent forms of cocaine among young people as the price comes down and the purity goes up.

A gram of "snortable" cocaine, which is about half a thimbleful, as recently as last year sold for $125. The widely cited figure today is $60 to $70.

"A few years ago, if you got 12 to 15 percent cocaine, you felt pretty good," said Det. William Larman of the D.C. narcotics squad. "Now, we're making street deals of 35 to 40 percent cocaine." The remainder of the drug is various powdery fillers, sometimes including anesthetics to make the user believe the drug is stronger than it is.

Early this spring, Larman said, undercover police officers at a public high school in the District bought a gram of 90 percent pure cocaine for $50. "It's a buyer's market," he said.

A new smokable form, "crack," costs about $25 a vial. Unlike other forms of freebase, it does not require processing. It has not yet appeared in significant amounts in the Washington area, Larman said, but is common in New York and Los Angeles.

Crack evolved partly as a free-enterprise response to the fear of AIDS, because drug users, wary of sharing intravenous needles, wanted an equally potent form of the drug in a more convenient package. If anything, it turns out, smoking cocaine is more effective than injecting it, reaching the brain in eight seconds instead of 12.

If the user is a novice, said Dr. Martin Slutsky, head of the Dominion Hospital treatment center in Falls Church, "for $10 you can get wasted for the night."

While use of marijuana and hashish declined steadily among high school students between 1978 and last year, cocaine use continued its slow rise, said the President's Commission on Organized Crime. From 1983 to 1985, the proportion of high school seniors who had used the drug during the previous month increased from 4.9 percent to 6.7 percent.

"I was speaking at a Westchester area high school," said Fair Oaks' Gold, "talking about marijuana and other drugs, and a kid stands up and says, 'People here have tried marijuana, but we don't like marijuana.' 'Why is that?' I say. And he says, 'Because marijuana is an anti-SAT drug.' "

Cocaine, on the other hand, is perceived as boosting mental and physical ability. In an achievement-oriented era, many students think it helps on their college entrance exams.

"In the short run," said Dr. Jeffrey Rosecan, a drug researcher at Columbia Presbyterian Medical Center, "it seems to help people perform. People accept this about amphetamines. Why do they have such a hard time accepting it about cocaine?"

Another expert said performance enhancement occurs only when the user is bored or fatigued. With amphetamines, and probably cocaine as well, performance is increased to "pre-fatigue levels," said Dr. Marian M. Fischman of Johns Hopkins University.

It is the search for better performance, both mental and physical, that can lead to addiction in only a few weeks. "Once you get the notion in your head that it helps you perform, you're in trouble," Rosecan said. "It's a fine line between feeling that it helps you perform better and that you can't perform without it." When cocaine is sniffed into the nose, the first effect is numbness from the drug's properties as a local anesthetic. An occasional user, the day after a binge, described a sensation of having "no nose at all." This anesthetic effect, which made eye surgery painless in the 1880s, results from interference with the electrical signals passing through the nerves. The signals cannot get through, so sensation is temporarily lost.

Once the drug reaches the brain, quite the opposite occurs.

There is an immediate sense of power and competence, users say, as if thinking itself had been sped up.

If the cocaine is delivered by injection or smoking, the feeling is more intense.

"You know what it was like?" said a 27-year-old former "crack" user in New York. "You feel so incredibly good that regular life doesn't seem good enough. All your prob- lems disappeared for those 45 seconds. It's like a total orgasm of the brain."

In men, said cocaine specialist Dackis, the drug can induce "spontaneous ejaculation." This is an extreme version of a sensation that users and therapists call the "rush," which occurs only when the drug is smoked or injected.

The rush lasts only a few seconds, followed by a up to 20 minutes of a high. This short "half-life," as one scientist described it, leads people to use large amounts of cocaine more rapidly than with most other drugs.

The former user in New York, a $50,000- a-year television cameraman, kicked the habit with the help of one of several medications that seem to ease the craving and reduce depression. None of the existing theories fully explains why these medicines work. But scientists are beginning to agree that cocaine is a two-faced drug, first stimulating the pleasure center, then squeezing it dry.

Gold and Dackis, the Fair Oaks team, and other leading reseachers believe that the drug focuses on one particular brain chemical, dopamine.

Dopamine molecules are one of several chemicals that complete circuits in the brain, crossing the tiny fluid-filled gaps, or synapses, between nerve cells. To send a signal, a nerve cell releases thousands of dopamine molecules, which activate receptors on the next cell. Once the signal is sent, the dopamine molecules return to the synapse, where many of them are reabsorbed by the sending cell and saved for future use.

Cocaine blocks this reabsorbtion. Instead of being recycled, the dopamine molecules remain in the synapse, stimulating the receptor cell again and again. The circuit re- mains charged, and the body continues to sense the pleasure or power that the nerves were sending. The heart speeds up; blood pressure rises; sex drive increases.

Over time, however, the effect changes. As the recycling of dopamine continues to be blocked, the build-up in the synapse is washed away. The brain's supply is depleted -- "squeezed out," as Rosecan puts it. The sending cells cannot produce dopamine fast enough to make up for the loss. The pleasure circuits are dry.

"After a couple of weeks, there is a chemical imbalance in your brain," Rosecan said.

The receptor cells, meanwhile, become supersensitive, agitated, like someone waiting by a phone that refuses to ring. More receptor sites appear in a desperate effort to pick up signals. "They're saying, 'Give me dopamine,' " Dackis said. "And then they're saying, 'Go get cocaine,' because that will give them dopamine in the short run."

The user becomes depressed, and in a very literal sense he or she is physically unable to experience pleasure without more cocaine, which provides a temporary boost in dopamine levels. Scientists describe a "vicious cycle" in which cocaine is needed to experience pleasure, but using it only further depletes the dopamine supply in the pleasure center.

Until recently, many people did not consider the drug physically addictive because the symptoms of cocaine withdrawal are primarily psychological. Traditional definitions of addiction, as in the cases of alcohol or heroin, required physical symptoms of withdrawal.

"In terms of heroin," said Ron Clark, director of the District's Rap Inc. drug treatment program, quitting produces symptoms "like a real bad case of flu. The bones ache, you just feel terrible.

"With cocaine, it's depression."

"Cocaine," said Dr. Frank Gawin, a Yale University addiction expert, "is a physically addictive drug where alterations occur in the part of the brain that affects psychology. So the expression of the addiction is psychological."

Even five years ago, "people would go to ERs saying they're addicted to cocaine, and the people in the emergency rooms would say, 'No, that's impossible,' " Gold recalled. "I mean, you had to be there." At Fair Oaks, Gold and Dackis are using a drug called bromocriptine to help patients who are trying to quit cocaine but find the craving too great to resist. The drug is a temporary substitute for the dopamine that the body lacks, stimulating the agitated dopamine receptors.

In a double-blind study of 13 patients, in which neither the patients nor the physicians knew whether bromocriptine or a placebo was being administered, the drug was universally effective in reducing craving, Dackis said. Results of the study are to be presented this week to the American Psychiatric Association in Washington.

In 60 other patients who were not part of the study, the drug has eased depression and reduced craving, he said.

Oddly, although the drug stimulates dopamine receptors, it does not produce a high, and it does not appear to be addictive.

"It doesn't make sense," Dackis said, "which means our theory's wrong. There's something we've overlooked."

Most scientists agree that other brain chemicals, or neurotransmitters, are also involved in cocaine addiction, although probably to a lesser extent than dopamine. Some think that cocaine not only blocks reabsorption of dopamine, but also stimulates more production of the brain chemicals in the short term, resulting in the same super-charging of the pleasure center.

"I don't know how cocaine works," said Yale's Gawin. "We don't even know if dopamine is the pleaure-regulating system for certain."

Gawin and his colleagues are prescribing a different drug, the antidepressant desipramine, to ease cocaine withdrawal. Unlike bromocriptine, it has no short-term effect on the craving that addict feels. But after two weeks, when even the sight of a bowl of powdered sugar can send a recovering addict back to the drug, desipramine seems to reduce the craving.

"It's not hard to keep someone off cocaine in a hospital," said Gawin. But in the "real world," a craving can be triggered by "a particular neighborhood, a house, a particular friend, or seeing a white powder that looks like cocaine.

"That craving has to be experienced, without using cocaine, for lasting reductions."

A sister drug, imipramine, is being prescribed by Rosecan and his colleagues at Columbia Presbyterian. Besides easing the craving, he said, the drug "in some cases blocks the euphoria" of cocaine.

The therapy also includes two amino acids, L-tryptophan and L-tyrosine, which the body uses to manufacture dopamine and other brain chemicals.

"The amino acids restore the neurotransmitter depletion," Rosecan said, "and the imipramine seems to straighten out the receptors."

One former user, the New York television cameraman, said his drug dealer continued to try to sell him cocaine even after he had started Rosecan's treatment program. The dealer, it turned out, also was trying to reduce his cocaine use.

"He went and got imipramine on the black market," the former addict said, "and says it has helped." Whether cocaine has become a national problem because the drug itself is exceptionally addictive or because of a combination of social circumstances remains a matter of dispute.

Famous studies have shown that rats and monkeys given free access to cocaine will use it -- instead of eating or drinking -- until they die, which they will not do with any other drug.

In early experiments, many by Dr. Roy Wise of Concordia University in Montreal, an electrode implanted in the rat's or monkey's brain could be activated by the animal's pressing a lever. Depending on where the electrode was implanted, pressing the lever produced various sensations. This allowed scientists to find the pleasure circuit.

In later experiments, the electrode in the brain was replaced by a piece of stainless steel tubing attached to a drug reservoir, verifying that chemicals stimulate the pleasure center.

And in similar experiments in which the drug is delivered intravenously, these animals pass up food and water and simply continue to "lever-press," as the researchers put it. "Given 24-hour-a-day free access to cocaine, they kill themselves," Wise said.

"Oh, sure, the monkey people will tell you monkeys will self-administer the drug until they die," said Dr. Reese Jones of Langley Porter Institute of the University of San Francisco, who has been studying drug abuse for more than two decades. In his experience, however, cocaine's effect is contingent on a combination of factors, including the social setting in which it is used.

"In the lab, it's not a dramatic drug," he said. "If you came into our lab right after someone in one room was given an intravenous injection of cocaine, and someone in another room had smoked a joint, and someone in another room had drunk a little alcohol, you couldn't tell the three people apart.

"In an hour or two, people are asleep. This is quite different from the 'Saturday Night Live' stereotype of climbing the walls.

"It's nothing that's particularly unique to cocaine. When you're alone at home and drink alcohol, it has quite a different effect than at a party with a lot of good people."

While it may be possible to make anyone an addict by injecting cocaine or providing large amounts of the drug, it is rare for all the factors that lead to addiction to come together, he said. "Being vulnerable is one thing. But one specific thing about cocaine is that you have to have it available. To get into a predicament that needs treatment, you need money, or being involved in the coke trade.

"The simple model that one sniff of cocaine and you're off to the races, no drug is like that."

Why have some people tried the drug and claim to feel little if any effect? Why do others use the drug occasionally without become addicted? And why do still others become hopelessly dependent? "That's the $64,000 question," Rosecan said.

"Simplistic statements like cocaine is the most addictive substance known to man might make good press, but they beg questions," said Yale's Gawin. "In animals self-administering it, it might be. But in middle America with occasional use, who knows?"

Concordia University's Wise, who has done animal experiments with cocaine, said it is virtually impossible for someone to use cocaine and get no sensation. "They probably didn't get much drug," he said.

As for those who don't get addicted: "I don't think with cocaine that there are people who are immune, if it weren't limited by price." There is also another way of looking at it. A small creature in Africa demonstrates on a much more primitive scale how animals of the same species can evolve with different biological priorities.

"In the African dung beetle," said evolutionary theorist Joseph E. Earley of Georgetown University, "there are two kinds of males. There's a little tiny one, and a great big fierce one with horns."

About 10 percent of the male dung beetles are of the small variety. Although the large ones are usually more successful in mating, occasionally, while two large male beetles are fighting for a female, a small male will "sneak in and get through."

Earley's point is that there are "varying strategies" of biological survival. Large beetles and small beetles, pleasure from drugs and pleasure from other things. And while the biological force that can lead to cocaine addition may be a strong one, it is not the only one.

In humans, as Wise also points out, pleasure is much more complicated. Saying no, in the language of the drug culture, can itself be a rush. "There are some people," Wise said, "who have a great deal of self-esteem based on their ability to resist temptation, to resist a drug."o weeks, when even the sight of a bowl of powdered sugar can send a recovering addict back to the drug, desipramine seems to reduce the craving.

"It's not hard to keep someone off cocaine in a hospital," said Gawin. But in the "real world," a craving can be triggered by "a particular neighborhood, a house, a particular friend, or seeing a white powder that looks like cocaine.

"That craving has to be experienced, without using cocaine, for lasting reductions."

A sister drug, imipramine, is being pre- scribed by Rosecan and his colleagues at Columbia Presbyterian. Besides easing the craving, he said, the drug "in some cases blocks the euphoria" of cocaine.

The therapy also includes two amino acids, L-tryptophan and L-tyrosine, which the body uses to manufacture dopamine and other brain chemicals.

"The amino acids restore the neurotransmitter depletion," Rosecan said, "and the imipramine seems to straighten out the receptors."

One former user, the New York television cameraman, said his drug dealer continued to try to sell him cocaine even after he had started Rosecan's treatment pro- gram. The dealer, it turned out, also was trying to reduce his cocaine use.

"He went and got imipramine on the black market," the former addict said, "and says it has helped." Whether cocaine has become a national problem because the drug itself is exceptionally addictive or because of a combination of social circumstances remains a matter of dispute.

Famous studies have shown that rats and monkeys given free access to cocaine will use it -- instead of eating or drinking -- until they die, which they will not do with any other drug."It's a fine line between feeling that it helps you perform better and that you can't perform without it." -- Dr. Jeffrey Rosecan, Columbia Presbyterian Medical Center

In early experiments, many by Dr. Roy Wise of Concordia University in Montreal, an electrode implanted in the rat's or monkey's brain could be activated by the animal's pressing a lever. Depending on where the electrode was implanted, pressing the lever produced various sensations. This allowed scientists to find the pleasure circuit.

In later experiments, the electrode in the brain was replaced by a piece of stainless steel tubing attached to a drug reservoir, verifying that chemicals stimulate the pleasure center.

And in similar experiments in which the drug is delivered intravenously, these animals pass up food and water and simply continue to "lever-press," as the researchers put it. "Given 24-hour-a-day free access to cocaine, they kill themselves," Wise said.

"Oh, sure, the monkey people will tell you monkeys will self-administer the drug until they die," said Dr. Reese Jones of Langley Porter Institute of the University of San Francisco, who has been studying drug abuse for more than two decades. In his experience, however, cocaine's effect is contingent on a combination of factors, including the social setting in which it is used.

"In the lab, it's not a dramatic drug," he "One specific thing about cocaine is that you have to have it available. To get into a predicament that needs treatment, you need money." -- Dr. Reese Jones, Langley Porter Institute said. "If you came into our lab right after someone in one room was given an intravenous injection of cocaine, and someone in another room had smoked a joint, and someone in another room had drunk a little alcohol, you couldn't tell the three people apart.

"In an hour or two, people are asleep. This is quite different from the 'Saturday Night Live' stereotype of climbing the walls.

"It's nothing that's particularly unique to cocaine. When you're alone at home and drink alcohol, it has quite a different effect than at a party with a lot of good people."

While it may be possible to make anyone an addict by injecting cocaine or providing large amounts of the drug, it is rare for all the factors that lead to addiction to come together, he said. "Being vulnerable is one thing. But one specific thing about cocaine is that you have to have it available. To get into a predicament that needs treatment, you need money, or being involved in the coke trade.

"The simple model that one sniff of cocaine and you're off to the races, no drug is like that."

Why have some people tried the drug and claim to feel little if any effect? Why do others use the drug occasionally without become addicted? And why do still others become hopelessly dependent? "That's the $64,000 question," Rosecan said.

"Simplistic statements like cocaine is the most addictive substance known to man might make good press, but they beg questions," said Yale's Gawin. "In animals self-administering it, it might be. But in middle America with occasional use, who knows?"

Concordia University's Wise, who has done animal experiments with cocaine, said it is virtually impossible for someone to use cocaine and get no sensation. "They probably didn't get much drug," he said.

As for those who don't get addicted: "I don't think with cocaine that there are people who are immune, if it weren't limited by price." There is also another way of looking at it. A small creature in Africa demonstrates on a much more primitive scale how animals of the same species can evolve with different biological priorities.

"In the African dung beetle," said evolutionary theorist Joseph E. Earley of Georgetown University, "there are two kinds of males. There's a little tiny one, and a great big fierce one with horns."

About 10 percent of the male dung beetles are of the small variety. Although the large ones are usually more successful in mating, occasionally, while two large male beetles are fighting for a female, a small male will "sneak in and get through."

Earley's point is that there are "varying strategies" of biological survival. Large beetles and small beetles, pleasure from drugs and pleasure from other things. And while the biological force that can lead to cocaine addition may be a strong one, it is not the only one.

In humans, as Wise also points out, pleasure is much more complicated. Saying no, in the language of the drug culture, can itself be a rush. "There are some people," Wise said, "who have a great deal of self-esteem based on their ability to resist temptation, to resist a drug."