Chapter 4. The Chemistry of Behavior: Neurotransmitters and Neuropharmacology

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By Joel Achenbach, The death last Sunday of Oscar-winning actor Philip Seymour Hoffman at age 46 focused media attention on the nationwide surge in heroin use and overdoses. But the very real heroin epidemic is framed by an even more dramatic increase since the beginning of the century in overdoses from pharmaceutical drugs known as opioids. These are, in effect, tandem epidemics — an addiction crisis driven by the powerful effects on the human brain of drugs derived from morphine. Prescription opioids are killing Americans at more than five times the rate that heroin is, according to the most recent numbers from the Centers for Disease Control and Prevention. These drugs are sold under such familiar brand names as OxyContin, Vicodin and Percocet and can be found in medicine cabinets in every precinct of American society. They’re also sold illicitly on the street or crushed and laced into heroin. There have been numerous efforts by law enforcement agencies to crack down on “pill mills” that dispense massive amounts of the pharmaceuticals, as well as regulations aimed at preventing users from “doctor shopping” to find someone who will write a prescription. Those efforts have had the unintended effect, officials say, of driving some people to heroin in recent years as their pill supply dries up. © 1996-2014 The Washington Post

Keyword: Drug Abuse
Link ID: 19218 - Posted: 02.08.2014

|By Carl Erik Fisher After 22 years of failed treatments, including rehabilitation, psychotherapy and an array of psychiatric medications, a middle-aged Dutch man decided to take an extraordinary step to fight his heroin addiction. He underwent an experimental brain surgery called deep brain stimulation (DBS). At the University of Amsterdam, researchers bored small holes in his skull and guided two long, thin probes deep into his head. The ends of the probes were lined with small electrodes, which were positioned in his nucleus accumbens, a brain area near the base of the skull that is associated with addiction. The scientists ran the connecting wires under his scalp, behind his ear and down to a battery pack sewn under the skin of his chest. Once turned on, the electrodes began delivering constant electrical pulses, much like a pacemaker, with the goal of altering the brain circuits thought to be causing his drug cravings. At first the stimulation intensified his desire for heroin, and he almost doubled his drug intake. But after the researchers adjusted the pulses, the cravings diminished, and he drastically cut down his heroin use. Neurosurgeries are now being pursued for a variety of mental illnesses. Initially developed in the 1980s to treat movement disorders, including Parkinson's disease, DBS is today used to treat depression, dementia, obsessive-compulsive disorder, substance abuse and even obesity. Despite several success stories, many of these new ventures have attracted critics, and some skeptics have even called for an outright halt to this research. © 2014 Scientific American

Keyword: Drug Abuse; Aggression
Link ID: 19216 - Posted: 02.06.2014

By Deborah Kotz / Globe Staff Public health officials, politicians, and smoking researchers cheered the Wednesday announcement from CVS Caremark that they will stop selling cigarettes and other tobacco products at CVS pharmacy stores by October. President Obama, a former smoker, said CVS is setting a “powerful example” and that will help public health efforts to reduce smoking-related deaths and illnesses. The American Public Health Association called it a “historic decision,” and the American Association of Cancer Research called it a “visionary move.” Dozens of other anti-smoking organizations and medical organizations—whose physicians treat the lung cancer, emphysema, and heart disease caused by smoking—proferred their approval and hope that other big chain pharmacies would follow suit. “CVS made a very compelling argument today that if you’re in the business of healthcare, you shouldn’t be in the business of selling tobacco products,” said Vince Willmore, spokesperson for the Campaign for Tobacco-Free Kids. “We’ll be taking that argument to every store with a pharmacy to make sure this is a catalyst for them.” Whether the CVS decision will result in fewer smokers remains unknown, said Margaret Reid, who directs tobacco control efforts at the Boston Public Health Commission, but added that it will certainly make tobacco products less readily available to smokers. When Boston implemented a ban on tobacco sales in pharmacies five years ago, it resulted in 85 fewer tobacco retailers in the city—about a 10 percent drop in the number of places permitted to sell cigarettes, cigars, and chewing tobacco. © 2014 Boston Globe Media Partners, LLC

Keyword: Drug Abuse
Link ID: 19213 - Posted: 02.06.2014

One thing marijuana isn’t known to do is improve your memory. But there’s another reason why scientists believe it could fight Alzheimer’s disease. Gary Wenk, PhD, professor of neuroscience, immunology and medical genetics at Ohio State University, has studied how to combat brain inflammation for over 25 years. His research has led him to a class of compounds known as cannabinoids, which includes many of the common ingredients in marijuana. He says, throughout all of his research, cannabinoids have been the only class of drugs he’s found to work. What’s more, he believes early intervention may be the best way of fighting Alzheimer’s. Dr. Wenk doesn’t see cannabinoids – or anything else – as a cure. But he took the time to discuss with us how marijuana might prevent the disorder from developing. Q: What’s so important about brain inflammation? Over the past few years, there’s been a focus on inflammation in the brain as causing a lot more than Alzheimer’s. We now know it plays a role in ALS, Parkinson’s disease, AIDS, dementia, multiple sclerosis, autism, schizophrenia, etc. We’re beginning to see that inflammation in the brain, if it lasts too long, can be quite detrimental. And if you do anything, such as smoke a bunch of marijuana in your 20s and 30s, you may wipe out all of the inflammation in your brain and then things start over again. And you simply die of old age before inflammation becomes an issue for you. © 2013-2014 All rights reserved

Keyword: Alzheimers; Aggression
Link ID: 19207 - Posted: 02.05.2014

By JANE E. BRODY “Even 50 years after the first surgeon general’s report on smoking and health, we’re still finding out new ways that tobacco kills and maims people,” Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, recently told me. “It’s astonishing how bad it is.” Dr. Frieden and public health specialists everywhere are seeking better ways to help the 44 million Americans who still smoke to quit and to keep young people from getting hooked on cigarettes. “Fewer than 2 percent of doctors smoke. Why can’t we get to that rate in society as a whole?” he wondered. One reason: Smoking rates are highest among the poor, poorly educated and people with mental illness, populations hard to reach with educational messages and quit-smoking aids. But when I mentioned to Dr. Frieden, a former New York City health commissioner, that the city’s streets are filled with young adult smokers who appear to be well educated and well dressed, he said television seems to have had an outsize influence. Focus groups of white girls in New York private schools have suggested a “Sex in the City” effect, he said: Girls think smoking makes them look sexy. In the last two years, middle-aged men, too, have begun smoking in increasing numbers after a half-century decline. Dr. Frieden cited “Mad Men,” the popular TV series featuring admen in the early 1960s, when well over half of American men smoked. Dr. Frieden said that an antismoking effort begun in 2008 by the World Health Organization “can make a huge difference in curbing smoking, and we should fully implement what we know works.” The program is called Mpower: © 2014 The New York Times Company

Keyword: Drug Abuse
Link ID: 19170 - Posted: 01.27.2014

By Roni Jacobson Over the past 10 years the number of overdose deaths from prescription painkillers—also known as opioid analgesics—has tripled, from 4,000 people in 1999 to more than 15,000 people every year in the U.S. today. Prescription pain medication now causes more overdose deaths than heroin and cocaine combined. In 2010 one in 20 Americans older than age 12 reported taking painkillers recreationally; some steal from pharmacies or buy them from a dealer, but most have a doctor's prescription or gain access to pills through friends and relatives. Yet millions of people legitimately rely on these medications to cope with the crippling pain they face every day. How do we make sure prescription opioids are readily available to those who depend on them for medical relief but not so available that they become easily abused? Here we break down the steps taken at various levels—and the experts' recommendations for future interventions—to curb prescription opioid addiction and overdose in the U.S. © 2014 Scientific American

Keyword: Drug Abuse; Aggression
Link ID: 19159 - Posted: 01.22.2014

by Bethany Brookshire There are some scientific topics that are bound to generate excitement. A launch to the moon, a potential cure for cancer or any study involving chocolate will always make the news. And then of course there’s caffeine. More than half of Americans have a daily coffee habit, not to mention the boost offered by tea, soda, chocolate and energy drinks. We’d all love to believe that it has more benefit than just papering over a poor night’s sleep. This week, scientists reported that caffeine could give a jolt to memory consolidation, the step right after your brain acquires a memory. During memory consolidation, activity patterns laid down in your brain become more permanent. The study suggested that caffeine might perk up this stage of memory formation. But while it’s an interesting finding, the scientific brew may not be strong enough to justify your coffee habit. Caffeine is a great way to wake you up. It blocks the action of adenosine, a chemical messenger that promotes sleep. Caffeine also has indirect effects on other chemical messengers such as norepinephrine, the neurotransmitter that gives us our famous “fight or flight” response. The net result is increased attention, wakefulness and faster responses. But attention, focus and response time are not memory. And previous studies of memory, says neuroscientist Michael Yassa, the lead author on the new study, were “all over the place.” So Yassa, then at Johns Hopkins University (he’s now at the University of California, Irvine), and undergraduate student Daniel Borota decided to study the effects of caffeine on memory “in a rigorous way.” © Society for Science & the Public 2000 - 2014

Keyword: Learning & Memory; Aggression
Link ID: 19154 - Posted: 01.20.2014

US President Barack Obama has said smoking marijuana is no more dangerous than alcohol, but still called it a "bad idea". Speaking to The New Yorker magazine, he said it was wrong to think legalising the drug would be "a panacea" that could solve many social problems. Mr Obama was referring to recent legalisation of marijuana in the states of Colorado and Washington. He has previously admitted using the drug when he was young. "As has been well documented, I smoked pot as a kid, and I view it as a bad habit and a vice, not very different from the cigarettes that I smoked as a young person up through a big chunk of my adult life," Mr Obama said. But he added that in terms of its impact on the individual consumer "I don't think it is more dangerous than alcohol". He also said that poor people - many of them African Americans and Latinos - were disproportionately punished for marijuana use, whereas middle-class users mostly escaped harsh penalties. "It's important for society not to have a situation in which a large portion of people have at one time or another broken the law and only a select few get punished." Mr Obama described the legalisation of marijuana in Colorado and Washington as a challenging "experiment". BBC © 2014

Keyword: Drug Abuse
Link ID: 19153 - Posted: 01.20.2014

By SABRINA TAVERNISE WASHINGTON — In a broad review of scientific literature, the nation’s top doctor has concluded that cigarette smoking — long known to cause lung cancer and heart disease — also causes diabetes, colorectal and liver cancers, erectile dysfunction and ectopic pregnancy. In a report to the nation to be released on Friday, the acting surgeon general, Dr. Boris D. Lushniak, significantly expanded the list of illnesses that cigarette smoking has been scientifically proved to cause. The other health problems the report names are vision loss, tuberculosis, rheumatoid arthritis, impaired immune function and cleft palates in children of women who smoke. Smoking has been known to be associated with these illnesses, but the report was the first time the federal government concluded that smoking causes them. The finding does not mean that smoking causes all cases of the health problems and diseases listed in the report, but that some of the cases would not have happened without smoking. The surgeon general has added to the list of smoking-related diseases before. Bladder cancer was added in 1990 and cervical cancer in 2004. When President Nixon signed the National Cancer Act many expected quick results, comparing the effort to the one that put man on the moon. After 42 years, what progress have we made? The report is not legally binding, but is broadly held as a standard for scientific evidence among researchers and policy makers. Experts not involved in writing the report said the findings were a comprehensive summary of the most current scientific evidence, and while they might not be surprising to researchers, they were intended to inform the public as well as doctors and other medical professionals about the newest proven risks of smoking. © 2014 The New York Times Company

Keyword: Drug Abuse
Link ID: 19149 - Posted: 01.18.2014

By Ashutosh Jogalekar Popular wisdom holds that caffeine enhances learning, alertness and retention, leading millions to consume coffee or caffeinated drinks before a challenging learning task such as attending a business strategy meeting or a demanding scientific presentation. However a new study in the journal Nature Neuroscience conducted by researchers from Johns Hopkins hints that when it comes to long-term memory and caffeine, timing may be everything; caffeine may enhance consolidation of memories only if it is consumed after a learning or memory challenge. In the study the authors conducted a randomized, double-blind controlled experiment in which 160 healthy female subjects between the ages of 18 and 30 were asked to perform a series of learning tasks. The subjects were handed cards with pictures of various random indoor and outdoor objects (for instance leaves, ducks and handbags) on them and asked to classify the objects as indoor or outdoor. Immediately after the task the volunteers were handed pills, either containing 200 mg of caffeine or placebo. Saliva samples to test for caffeine and its metabolites were collected after 1, 3 and 24 hours. After 24 hours the researchers tested the participants’ recollection of the past day’s test. Along with the items in the test (‘old’) they were presented with new items (‘foils’) and similar looking items (‘lures’), neither of which were part of the task. They were then asked to again classify the items as old, new and similar. There was a statistically significant percentage of volunteers in the caffeinated group that was more likely to mark the ‘similar’ items as ‘similar’ rather than ‘old’. That is, caffeinated participants were clearly able to distinguish much better between the old and the other items, indicating that they were retaining the memory of the old items much better than the people in the placebo group. © 2014 Scientific American,

Keyword: Learning & Memory; Aggression
Link ID: 19133 - Posted: 01.15.2014

By Matt McGrath Environment correspondent, BBC News Taking substances to enhance the brain is more popular among amateur athletes than taking drugs to boost the body. Researchers in Germany found that 15% of recreational triathletes admitted to brain doping, using prescription medicines that increase attention. Some 13% of competitors reported using physical enhancers like steroids or human growth hormone. Brain doping is more popular say the scientists, because many of the substances aren't banned. The research has been published in the journal Plos One. Previous studies have shown that, among amateur competitors, the use of performance-enhancing substances is widespread. This new work used the responses of almost 3,000 triathletes taking part in events in Germany, to analyse the broader picture of physical and cognitive doping. Researchers believe that many so-called "smart drugs" are being widely used to enhance mental functions outside the patients groups they have been designed to help. They are also concerned that competitors in a variety of sports may be using these substances to gain an edge. In the study, participants were asked whether they had used physical or brain-enhancing substances in the past 12 months. Overall, 13% said they had taken drugs like EPO, steroids, or growth hormones. BBC © 2014

Keyword: Drug Abuse; Aggression
Link ID: 19130 - Posted: 01.15.2014

By Scott O. Lilienfeld and Hal Arkowitz “Just say no.” In 1982 First Lady Nancy Reagan uttered those three words in response to a schoolgirl who wanted to know what she should say if someone offered her drugs. The first lady's suggestion soon became the clarion call for the adolescent drug prevention movement in the 1980s and beyond. Since then, schools around the country have instituted programs designed to discourage alcohol and drug use among youth—most of them targeting older elementary schoolchildren and a few addressing adolescents. There is good reason for concern about youth substance abuse. A large U.S. survey conducted in 2012 by psychologist Lloyd D. Johnston and his colleagues at the University of Michigan revealed that fully 24 percent of 12th graders had engaged in binge drinking (defined as five or more drinks on one occasion) in the past two weeks. Moreover, 42 percent had consumed at least some alcohol in the past month, as had 11 percent of eighth graders and 28 percent of high school sophomores. In addition, 1 percent of 12th graders had tried methamphetamine, and almost 3 percent had used cocaine in the past year. In an attempt to reduce these figures, substance abuse prevention programs often educate pupils regarding the perils of drug use, teach students social skills to resist peer pressure to experiment, and help young people feel that saying no is socially acceptable. All the approaches seem sensible on the surface, so policy makers, teachers and parents typically assume they work. Yet it turns out that approaches involving social interaction work better than the ones emphasizing education. That finding may explain why the most popular prevention program has been found to be ineffective—and may even heighten the use of some substances among teens. © 2014 Scientific American,

Keyword: Drug Abuse
Link ID: 19128 - Posted: 01.14.2014

Ian Sample, science correspondent A cup or two of coffee could boost the brain's ability to store long-term memories, researchers in the US claim. People who had a shot of caffeine after looking at a series of pictures were better at distinguishing them from similar images in tests the next day, the scientists found. The task gives a measure of how precisely information is stored in the brain, which helps with a process called pattern separation which can be crucial in everyday situations. If the effect is real, and some scientists are doubtful, then it would add memory enhancement to the growing list of benefits that moderate caffeine consumption seems to provide. Michael Yassa, a neuroscientist who led the study at Johns Hopkins University in Baltimore, said the ability to separate patterns was vital for discriminating between similar scenarios and experiences in life. "If you park in the same parking lot every day, the spot you choose can look the same as many others. But when you go and look for your car, you need to look for where you parked it today, not where you parked it yesterday," he said. Writing in the journal Nature Neuroscience, Yassa described how 44 volunteers who were not heavy caffeine consumers and had abstained for at least a day were shown a rapid sequence of pictures on a computer screen. The pictures included a huge range of items, such as a hammer, a chair, an apple, a seahorse, a rubber duck and a car. © 2014 Guardian News and Media Limited

Keyword: Learning & Memory; Aggression
Link ID: 19122 - Posted: 01.13.2014

By NICHOLAS BAKALAR We know that smoking is bad for you — and that it ages you prematurely. Now a study provides photographic evidence for this claim. Scientists gathered health and lifestyle information on 79 pairs of identical adult twins who fit into one of three groups: a pair in which one was a smoker and the other had never smoked; a pair in which both were smokers; or a pair in which both were smokers but with at least a 5-year difference in the duration of their smoking habit. They photographed them and had independent judges rate the pictures side-by-side for wrinkles, crow’s feet, jowls, bags under the eyes, creases around the nose, lines around the lips and other evidence of aging skin. The differences in some other factors that can age skin prematurely — alcohol consumption, sunscreen use and perceived stress at work — were statistically insignificant between twin pairs. But the judges’ decisions on which twin looked older coincided almost perfectly with their smoking histories. “The purpose of this study was to offer scientific evidence that smoking changes not only longevity, but also quality of appearance,” said the senior author, Dr. Bahman Guyuron, chairman of the plastic surgery department at University Hospital, Case Medical Center in Cleveland. “It is harmful any way you look at it.” Copyright 2014 The New York Times Company

Keyword: Drug Abuse
Link ID: 19118 - Posted: 01.11.2014

By Ashutosh Jogalekar Often you will hear people talking about why drugs are expensive: it’s the greedy pharmaceutical companies, the patent system, the government, capitalism itself. All these factors contribute to increasing the price of a drug, but one very important factor often gets entirely overlooked: Drugs are expensive because the science of drug discovery is hard. And it’s just getting harder. In fact purely on a scientific level, taking a drug all the way from initial discovery to market is considered harder than putting a man on the moon, and there’s more than a shred of truth to this contention. In this series of posts I will try to highlight some of the purely scientific challenges inherent in the discovery of new medicines. I am hoping that this will make laymen appreciate a little better why the cost of drugs doesn’t have everything to do with profit and power and much to do with scientific ignorance and difficulty; as one leading scientist I know quips, “Drugs are not expensive because we are evil, they are expensive because we are stupid.” I could actually end this post right here by stating one simple, predominant reason why the science of drug discovery is so tortuous: it’s because biology is complex. The second reason is because we are dealing with a classic multiple variable optimization problem, except that the variables to be optimized again pertain to a very poorly understood, complex and unpredictable system. The longer answer will be more interesting. The simple fact is that we still haven’t figured out the workings of biological systems – the human body in this case – to an extent that allows us to rationally and predictably modify, mitigate or cure their ills using small organic molecules. That we have been able to do so to an unusually successful degree is a tribute to both human ingenuity and plain good luck. But there’s still a very long way to go. © 2014 Scientific American

Keyword: Miscellaneous
Link ID: 19105 - Posted: 01.07.2014

by Alyssa Botelho Women with breast cancer often enjoy several years in remission, only to then be given the devastating news that they have developed brain tumours. Now we are finally starting to understand how breast cancer cells are able to spread undetected in the brain: they masquerade as neurons and hijack their energy supply. For every tumour that originates in the brain, 10 arrive there from other organ systems. Understanding how tumours spread, or metastasise, and survive in the brain is important because the survival rate of people with brain metastases is poor – only a fifth are still alive a year after being diagnosed. Rahul Jandial, a neurosurgeon at the City of Hope Cancer Center in Duarte, California, wanted to explore how breast cancer cells are able to cross the blood-brain barrier and escape destruction by the immune system. "If, by chance, a malignant breast cancer cell swimming in the bloodstream crossed into the brain, how would it survive in a completely new, foreign habitat?" Jandial says. He and his team wondered if breast cancer cells that could use the resources around them – neurotransmitters and other chemicals in the brain – would be the ones that survived and flourished. To test the idea, they took samples of metastatic breast cancer cells from the brains of several women and grew them in the lab. They compared the expression of proteins involved in detecting and absorbing GABA – a common neurotransmitter that neurons convert into energy – in these cells with what happens in non-metastatic breast cancer cells. © Copyright Reed Business Information Ltd

Keyword: Miscellaneous
Link ID: 19102 - Posted: 01.07.2014

by Bethany Brookshire When most people think of the quintessential lab mouse, they think of a little white mouse with red eyes. Soft fur. A timid nature. But scientists think of something very different. This mouse is black, small and fast, with pink ears and a pinkish tail. It’s got black eyes to match. The fur may be soft, but the temper sure isn’t. This is the C57 Black 6 mouse. Each Black 6 mouse should be almost identical to every other Black 6 mouse. They have been bred to their own siblings for hundreds of generations, so there should be very few genetic differences left. But even supposedly identical mouse strains have their differences. These take the form of mutations in single DNA base pairs that accumulate in different populations. Recently, researchers showed that one of these tiny changes in a single gene was enough to produce a huge difference in how two groups of Black 6 mice respond to drugs. And the authors identified a surprising number of other small DNA differences still waiting to be explored. On one level, the new work offers scientists a novel tool for identifying genes that could relate to behaviors. But it also serves as a warning. “Identical” mouse populations aren’t as alike as many scientists had assumed. The Black 6, the most common lab mouse in the United States, is used for everything from drug abuse studies to cancer research. The Black 6 is also the reference strain for the Mouse Genome Sequencing Consortium. Whenever scientists discover a new genetic change in a mouse strain, they compare it first against the Black 6. And it’s the mouse used by the International Knockout Mouse Consortium (now the International Mouse Phenotyping Consortium), which keep a library of mouse embryos with different deleted genes. The Allen Brain Atlas, a database of neuroanatomy and gene activity throughout the mouse brain, relies on the Black 6 as well. © Society for Science & the Public 2000 - 2014

Keyword: Genes & Behavior; Aggression
Link ID: 19097 - Posted: 01.04.2014

People with severe mental illness such as schizophrenia or bipolar disorder have a higher risk for substance use, especially cigarette smoking, and protective factors usually associated with lower rates of substance use do not exist in severe mental illness, according to a new study funded by the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health. Estimates based on past studies suggest that people diagnosed with mood or anxiety disorders are about twice as likely as the general population to also suffer from a substance use disorder. Statistics from the 2012 National Survey on Drug Use and Health indicate close to 8.4 million External Web Site Policy adults in the United States have both a mental and substance use disorder. However, only 7.9 percent of people receive treatment for both conditions, and 53.7 percent receive no treatment at all, the statistics External Web Site Policy indicate. “Drug use impacts many of the same brain circuits that are disrupted in severe mental disorders such as schizophrenia,” said NIDA Director Dr. Nora D. Volkow. “While we cannot always prove a connection or causality, we do know that certain mental disorders are risk factors for subsequent substance use disorders, and vice versa.” In the current study, 9,142 people diagnosed with schizophrenia, schizoaffective disorder, or bipolar disorder with psychotic features, and 10,195 controls matched to participants according to geographic region, were selected using the Genomic Psychiatry Cohort program. Mental disorder diagnoses were confirmed using the Diagnostic Interview for Psychosis and Affective Disorder (DI-PAD), and controls were screened to verify the absence of schizophrenia or bipolar disorder in themselves or close family members. The DI-PAD was also used for all participants to determine substance use rates.

Keyword: Schizophrenia; Aggression
Link ID: 19090 - Posted: 01.04.2014

by Paul Heltzel Have you ever looked at your dorsal fin — I mean, really looked at it? Dolphins, nature’s playful jokers, apparently have a little habit they’ve been keeping a secret: They get high. A BBC film crew recently captured some unusual footage of dolphins passing a puffer fish between them. The fish then secretes a toxin — a defense mechanism — which the dolphins appear to enjoy — a lot. As the dolphins nudged the puffer fish back and forth, they fell into a trancelike state, reports the Guardian. “At one point the dolphins are seen floating just underneath the water’s surface, apparently mesmerized by their own reflections,” according to the Guardian. Filmmaker John Downer cleverly disguised underwater cameras as squid, tuna and other dolphins to record the footage. Downer told the BBC the dolphins handled the puffer carefully, so they wouldn’t hurt or kill it. “The dolphins were specifically going for the puffers,” Downer said, “and deliberately handling them with care.” © 2014 Discovery Communications, LLC.

Keyword: Drug Abuse
Link ID: 19088 - Posted: 01.02.2014

For tobacco hornworms, bad breath might be the key to surviving the night. As their name suggests, these desert-dwelling caterpillars (larvae of the Manduca sexta moth) regularly chomp on nicotine-laced tobacco leaves. Scientists observed that caterpillars feeding on genetically modified, nicotine-free tobacco plants were more likely to disappear during the night than those chowing down on regular tobacco, leading them to suspect that the hornworms might be repurposing the toxic chemical to defend themselves against nocturnal predators like wolf spiders (Camptocosa parallela, pictured above feasting on a larva). The researchers investigated a gene called CYP6B46, which is active in the hornworm’s gut. Turning the gene off resulted in higher nicotine levels in the hornworms’ poop, suggesting that the gene helps the larvae avoid excreting the chemical by pumping it out of their guts and into their blood. The caterpillars had to be exuding the toxic nicotine somehow, so the scientists gave them an insect version of a breathalyzer test and discovered that they breathe it out with every exhale, the team reports online today in the Proceedings of the National Academy of Sciences. This “toxic halitosis” repelled wolf spiders, which actually flee from caterpillars with nicotine on their breath, as you can see in this video. Still, bad breath is no guarantee of a long life: It didn’t deter some of the hornworms’ other predators, including big-eyed bugs and antlion larvae. © 2013 American Association for the Advancement of Science

Keyword: Neurotoxins
Link ID: 19078 - Posted: 12.31.2013