二套周日19:00首播 一套周五15:10 十套12:00、19:00重播

Nicotine:the desirable drug    
  Pure Nicotine,just three drops can kill an adult. Yet every day, millions of people take it into their lungs.

  These are tobacco plants, the only natural source of nicotine. We now understand that it's this substance that keeps people smoking, despite all the warnings. It one of the most addictive drugs we know.

  As tobacco cigarette burns, a potpourri of 4000 chemicals is released, including carbon monoxide and hydrocyanic acid. It's there, rather than nicotine that is responsible for the major health problems like lung cancer, heart disease, and mphysema. But the thing that gets you hooked on the whole vaporous cocktail is nicotine.

  While inhaling deeply, you also get more of the carbon monoxide and tars that cause lung and heart disease. So the cigarettes you've bought to lessen the impact on your health may actually be worse for you.

  While the pharmaceutical industry gears up to exploit nicotine's positive side, others are uncovering the havoc the drug can cause, especially in the very young.

  Pregnant women are warned not to smoke. It lowers the baby's birth weight. We've known for some tome that carbon monoxide in tobacco is the culprit here.

  But new research is showing that nicotine adds further, more insidious risks.

  Here's a mom who smoked during pregnancy. Her baby has a baby of normal weight. Do we need to be concerned about that baby or is weight the whole story? And it turns out that weight is not the whole story. In fact, it's very misleading indicator, more so with nicotine than with virtually any other kind of damaging event during gestation.

  The damage happens as the brain is developing. And nicotine again replaces acetylcholine at a critical moment. And nicotine again replaces acetylcholine at a critical moment.

  Building a brain is all about making the right connections. In particular it hinges on the way things called axon form a nerve network.

  First young nerve cells move towards their allotted sites in the brain. Once there, they'll receive a signal, a burst of acetylcholine. That activates the next stage. Each nerve cell sends out an axon, a long fiber, to make contact with a target cell and build connections. If nicotine is introduced, the cells get confused and activate the process too soon.

  It's done it at the wrong time. It's done it before you've got the right number of cells. Plus, it's now sending out its offshoot, its axon, to find its target cell, but the target cell may not even have migrated into the right lace yet. So the axon gets lost and winds up innervating the wrong cells. So it's like you have a radio with the wires going to the wrong places, and naturally, that causes functional disruption.

  We've now got a good idea, which regions of the brain are prone to this faulty wiring. One is the respiratory center and may explain a known link between smoking and Sudden Infant Death Syndrome.

  It turns out that u can account for probably over half of Sudden Infant Death from tobacco use. In fact, a very carefully controlled study done in Sweden attributed 70 percent of Sudden Infant Death to tobacco smoking. And that's the number one killer of infants under one year of age.

  What triggers Sudden Infant Death is a period of asphyxia during sleep, when the baby slows or stops breathing.

  Normally the brain's respiration center will detect the plummeting wxyen levels and make baby breathe deeper. At the same time, a rush of adrenalin makes the heart beat faster.

  But in nicotine babies, both these survival systems may be incorrectly wired and the baby simply suffocates.

  To those watching this program who think that quitting has nothing to do with them, just remember, the ads are right when they say cigarettes help a smoker cope with stress. We need to think carefully about what happens when someone quits. Lives may depend on it - and not just the smoker's.