What’s a Neurotransmitter, Anyway?

A brief guide for the perplexed.

A neurotransmitter is a chemical substance that carries impulses from one nerve cell to another. Neurotransmitters are manufactured by the body and are released from storage sacs in the nerve cells. A tiny junction, called the synaptic gap, lies between brain cells. (Think of Michelangelo’s Sistine Chapel, with the finger of Adam and the finger of God not quite touching, yet conveying energy and information.)

Neurotransmitters squirt across the synaptic gap, and this shower of chemical messengers lands on a field of tiny bumps attached to the surface of the nerve cell on the other side of the synaptic gap. These bumps are receptors, and they have distinctive shapes. Picture these receptors, brain researcher Candace Pert has suggested, as a field of lily pads floating on the outer oily surface of the cell.

Neurotransmitter molecules bind themselves tightly to these receptors. The fact that certain drugs of abuse also lock tightly into existing receptors, and send messages to nerve cells in the brain, is the key to the mystery of addiction.

The fact that certain drugs essentially “fool” receptors into receiving them is one of the most important and far-reaching discoveries in the history of modern science. It is the reason why even minute amounts of certain drugs can have such powerful effects on the human nervous system. The lock-and-key arrangement of neurotransmitters and their receptors is the fundamental architecture of action in the brain. Glandular cells are studded with receptors, and many of the hormones have their own receptors as well. If the drug fits the receptor and elicits a response, it is called an agonist. If it simply blocks the receptor site without stimulating a response, it is an antagonist. Still other neurotransmitters have only a secondary effect, causing the target cell to release other kinds of neurotransmitters and hormones.

Two of the most important neurotransmitters are serotonin and dopamine. The unfolding story of addiction science, at bottom, is the story of what has been learned about the nature and function of such chemicals, and the many and varied ways they effect the pleasure and reward centers in our brains.

In 1948, three researchers—Maurice Rapport, Arda Green, and Irvine Page—were looking for a better blood pressure medication. Instead, they managed to isolate a naturally occurring compound in beef blood called serotonin (pronounced sarah-tóne-in), and known chemically as 5-hydroxytryptamine, or simply 5-HT. The researchers determined that serotonin was involved in vasoconstriction, or narrowing of the blood vessels, and in that respect resembled another important chemical messenger in the brain—epinephrine, better known as adrenaline.

Even though there is at most 10 milligrams of the substance in our bodies, serotonin turned out to be one of nature’s signature chemicals—a chemical of thought, movement and behavior, as well as digestion, ejaculation, and evacuation. The body’s all-purpose neurotransmitter, involved in sleep, mood, appetite, among dozens of other functions. The cortex, the limbic system, the brain stem, the gut, the genitals, the bowels: serotonin is a key chemical messenger in all of it.

Another key neurotransmitter—dopamine—is considered to be one of the brain’s primary “pleasure chemicals,” and is found in areas of the brain linked to experiences of joy and reward.

Dopamine pathways play a role in carrying signals related to attention, movement, problem solving, pleasure, and the anticipation of rewarding experiences. Dopamine is one of the reasons why, after you have a pleasurable experience with food, drink, sex, or certain drugs, you are likely to feel a desire to repeat the experience. Dopamine is implicated in not just the drug high, but in the craving that accompanies withdrawal as well.

Feelings of pleasure, or joy, are natural drug highs. The fact that they are produced by chemical alterations in brain state does not make the fear or the pleasure feel any less real.

Excerpted from The Chemical Carousel: What Science Tells Us About Beating Addiction by Dirk Hanson © 2008


Photo Credit: NIDA

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Common Medicines That Can Kill You [Guest Post]

Legal but lethal.

[Today’s post was written by Kat Sanders, who regularly blogs on the topic of pharmacy technician certification. She welcomes your comments and questions at her email address: katsanders25@gmail.com.]

Medicines are supposed to save lives, but as with all things that are not used responsibly, they end up killing people more often than not when they are abused. It’s not just illegal drugs that kill; even the ones that are prescribed have the potential to become dangerous when they are not used as they are supposed to be. While we know that heroin, crack and other illegal substances cause death in the event of an overdose, we are not aware of many others that are relatively unknown, but just as dangerous. The below list is not exhaustive but details just a few of the drugs that could lead to death if abused.

NPF: Non-Pharmaceutical Fentanyl has been responsible for more than 1000 deaths (those that have been reported--there are definitely going to be many more that went unnoticed or unreported) between 2005 and 2007, according to the US Center for Disease Control and Prevention (CDC). NPF is a painkiller, one that is also illegally produced and sold because of its narcotic effects. Since it is much cheaper than heroin, sales are high, as are the deaths that it is responsible for. What people do not realize is that when this drug is produced illegally, it is 30 to 50 times more potent and risky than heroin.

Codeine: We would hardly think that the cough syrups we obtain over the counter could end up killing us, but the codeine they contain is a narcotic that causes hallucinations if taken in large amounts. And when cough syrups are abused, they could end up being potentially dangerous, like the case of Chad Butler, the rapper more popularly known as Pimp C. The singer already suffered from sleep apnea, and large amounts of codeine combined with sleep apnea is apparently enough to cause respiratory problems and cause death.

Acetaminophen (Paracetamol): While paracetamol alone cannot cause death, if you are a habitual drinker, your liver is already weak and damaged. And when you take large doses of paracetamol under such conditions, you may start feeling the symptoms in a day or two; you may experience a stomach ache, vomit, and feel pretty ill. Death, if it occurs, happens after four or five days after the overdose, if you do not take any treatment at all in the interim.

Opioid painkillers and Anti-depressants: This combination was responsible for killing up and coming actor Heath Ledger. The star, who was said to be increasingly despondent and depressed, was on anti-anxiety drugs and painkillers as part of his prescription. An overdose (a combination of six different drugs that included sedatives and painkillers) found him dead, just before the release of the blockbuster movie The Dark Knight, the latest in the Batman series and the one that saw him winning a posthumous Oscar for his devilish portrayal of the Joker.
The CDC reports that accidental drug overdoses are responsible for the death of more than 22,000 Americans every year. In fact, it is the second leading cause of preventable deaths, next to automobile accidents. And this is why we need to be extra careful and exercise caution when handling drugs and medicines.

Photo Credit: Canwest News Service

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Friday File

Book and Blog Recommendations

Books

A decade ago, Dr. Jill Bolte Taylor, a brain researcher at Harvard Medical School and a national spokesperson for the Harvard Brain Bank, suffered a massive stroke at the age of 37. Unable to walk, talk, read, or write, Dr. Taylor underwent an 8-year recovery and narrates the story of her recovery in her book , My Stroke of Insight.

The book’s jacket copy explains: “As the damaged left side of her brain—the rational, grounded, detail-and-time oriented side—swung in and out of function, Taylor alternated between two distinct and opposite realities: the euphoric nirvana of the intuitive and kinesthetic right brain, in which she felt a sense of complete well-being and peace, and the logical, sequential left brain, which recognized Jill was having a stroke and enabled her to seek help before she was lost completely. “

As reporter Robert Koehler writes: “This book is about the wonder of being human and as such is a plea and a prayer that we strive to be equal to how big we really are. What a piece of work is man — 50 trillion cells functioning in purposeful harmony.”

Stroke patients, victims of brain injuries, medical practitioners, and the general reading public will find invaluable insights and recommendations in this book.

Blogs

The mission of Corpus Callosum, a science blog maintained by an anonymous psychiatrist who works at a community hospital, is “to develop connections between hard science and social science, using linear thinking and intuition; and to explore the relative merits of spontaneity vs. strategy.” The blog intelligently covers a broad range of general-interest topics, including social commentary, neuroscience, politics, and science news.

Corpus Callosum also regularly features excellent graphics and photographs, and is written in a reasoned, straightforward and easy-to-digest style. As a bonus, the site features a deep and high-quality blogroll.

They Inhaled

The "Nice People Take Drugs" campaign.

From the UK charity Release comes the project called Nice People Take Drugs. The publicity campaign has caused significant controversy in Britain, as reported by the UK Guardian. Release says on its web site that its charter is to "campaign for changes to UK drug policy to bring about a fairer and more compassionate legal framework to manage drug use in our society."

An earlier, similar campaign, using the same slogan and photos of well-known people on bus advertisements, ended when the bus company removed the ads, fearing a public backlash.

1 in 25 Global Deaths Linked to Alcohol

Vodka kills more Russians than war, Lancet reports.

A team of researchers at the University of Toronto reported in Lancet that 3.8 % of global deaths could be attributed to alcohol. In Europe, the report stated, the rate of premature death from alcohol was 1 in 10 during 2004, the year studied. And in a related study, more than half of all premature deaths among adult males in Russia were attributable to booze.

The world health care burden, as spelled out by Dr. Jurgen Rehm and others at the University of Toronto, is staggering: “The costs associated with alcohol amount to more than 1% of the gross national product in high-income and middle-income countries, with the costs of social harm constituting a major proportion in addition to health costs.”

In a BBC News report,the study authors warned that the worldwide effect of alcohol-related disease was similar to that of smoking in prior decades. The report takes note of prior research indicating a health benefit from moderate drinking, stressing that any purported benefit is “far outweighed by the detrimental effects of alcohol on disease and injury.”

The Lancet study concludes that the overall mortality figures are “not surprising since global consumption is increasing, especially in the most populous countries of India and China.”

Professor Ian Gilmore of the Royal College of Physicians, quoted by the BBC, called the report “a global wake-up call,” and urged the adoption of “evidence-based measures” for reducing alcohol-related harm, such as price increases and advertising bans. “Many countries are investigating new ways to cut deaths and disease and reduce the burden on health services by using the price of alcohol to lower consumption,” Gilmore said. Pricing strategies have been used effectively in the past to lower cigarette consumption, researchers have noted.

In one of the Russian studies, Professor Richard Peto of the University of Oxford led a statistical analyses, concluding: “If current Russian death rates continue, then about 5% of all young women and 25% of all young men will die before age 55 years from the direct or indirect effects of drinking.” The Russian figures are also affected by the high rate of associated smoking in the former Soviet Union.

Peto added: “When Russian alcohol sales decreased by about a quarter, overall mortality of people of working age immediately decreased by nearly a quarter. This shows that when people who are at high risk of death from alcohol do change their habits, they immediately avoid most of the risk.”

Photo Credit: www.adaweb.net

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Friday File

Book and blog recommendations for the weekend.

Books

I just finished reading a splendid book, Barbara Oakley’s Evil Genes: Why Rome Fell, Hitler Rose, Enron Failed, and My Sister Stole My Mother’s Boyfriend. Oakley, a systems engineer at Oakland University in Michigan, has done a great service for interested non-scientists by picking apart the intricate genetics of psychopathy and antisocial behavior.

Primarily a history of borderline personality disorder and the “great men” who suffered from it, Oakley takes the “nature-nurture” debate to the next level, asserting that bad behavior is a genetic propensity triggered by environmental influences—precisely the argument I make about addiction in my book, The Chemical Carousel: What Science Tells Us About Beating Addiction.

Oakley deftly beats back the usual panoply of objections to genomic research—that it is a slippery slope leading to eugenics, or that it is an excuse for bad behavior. Even worse, for many people, Evil Genes suggests that individual ethics are largely biochemically determined. The “successfully sinister,” as she calls them, have a baffling ability to charm their way to the top, and the author suggests some evolutionary reasons why this might be so.

Overall, Oakley makes a strong, eye-opening case for the importance of modern neuroscience in the quest to understand human behavior. This book should come as a serious shock to a generation of lawyers, judges and forensic psychologists who have spent a lifetime adhering to the “blank slate” view of human nature, when the “bad seed” analogy appears to be closer to the truth.

Blogs

Check out Brain Blogger for a look at “Topics from Multidimensional BioPsychoSocial Perspectives,” as the site is subtitled. Recent posts include articles about antibiotic overuse, gender reassignment, autism, torture, proprioception, neural plasticity, and my own article on marijuana withdrawal, which has drawn a panoply of heated responses.

A fascinating site with a multidisciplinary perspective.

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Should I Tell My Boss?

Health help in the workplace.

It’s no secret: Times are tough. The situation at work is uncertain at best, downright Machiavellian at worst. According to a recent survey by the American Psychological Association (APA), the primary source of stress for 80 % of Americans is—you guessed it—money.

Health Matters at Work, a program developed by Community Health Charities, is offering a four-part video podcast series on addiction, depression, and stress in the workplace. The goal of the Health Matters at Work program is to enhance the ability of “employers, employees, and their loved ones to connect to credible information and resources to improve their health and their lives.”

The podcast series focuses on work-related resources available through Mental Health America, the Depression and Bipolar Support Alliance, and the National Council on Alcoholism and Drug Dependence.

“The message we hope people hear,” said Robert Lindsey of the National Council on Alcoholism and Drug Dependence, “is that together we offer a broad network of support to people in communities across America, and we are all here for people that need our help.”

David Shern of Mental Health America said: “Mental Health is fundamental to health in every way. Increased levels of stress, depression, and anxiety all raise the risk of cardiovascular disease.”

Community Health Charities of America, located in Arlington, Virginia, is a consortium dedicated to assisting “people affected by a disability or chronic disease by uniting caring donors in the workplace with health issues and causes important to them and their families.”

A list of the group’s member charities can be found here.

Corporate partners include AARP, McDonalds, Exxon, HP, Siemens, and USA Today.


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