Chapter 5. Hormones and the Brain
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A randomized clinical trial of estrogen therapy in younger postmenopausal women, aged 50–55, has found no long-term risk or benefit to cognitive function. The National Institutes of Health-supported study, reported in JAMA Internal Medicine on June 24, 2013, looked at women taking conjugated equine estrogens, the most common type of postmenopausal hormone therapy in the United States. The earlier Women’s Health Initiative Memory Study (WHIMS) linked the same type of hormone therapy to cognitive decline and dementia in older postmenopausal women. The new findings come from the Women’s Health Initiative Memory Study of Younger Women (WHIMSY) trial and were reported by Mark A. Espeland, Ph.D., Wake Forest School of Medicine, Winston-Salem, N.C., on behalf of the academic research centers involved in the study. The study was funded primarily by the National Institute on Aging (NIA), along with the National Heart, Lung, and Blood Institute (NHLBI), both components of the NIH. “The WHIMS study found that estrogen-based postmenopausal hormone therapy produced deficits in cognitive function and increased risk for dementia when prescribed to women 65 and older,” said NIA Director Richard J. Hodes, M.D. “Researchers leading the WHIMSY study wanted to expand on those results by exploring the possibility of a window of opportunity whereby hormone therapy might promote or preserve brain health when given to younger women.” “In contrast to findings in older postmenopausal women, this study tells women that taking these types of estrogen-based hormone therapies for a relatively short period of time in their early postmenopausal years may not put them at increased risk for cognitive decline over the long term,” said Susan Resnick, Ph.D., chief of the Laboratory of Behavioral Neuroscience, in NIA’s Intramural Research Program and a co-author of the study. “Further, it is important to note that we did not find any cognitive benefit after long-term follow-up.”
By Brigid Schulte, Unlike the male pundits, politicians and even financiers who’ve opined freely recently about what they consider “natural” roles for mothers and fathers, with mom at home and dad at work, behavioral neuroscientist Kelly Lambert’s methodical approach has led her to a much more complicated conclusion. From her perch at Randolph-Macon College in rural Ashland, Va., Lambert has spent years designing elaborate experiments to test nurturing in both male and female rodents. She anesthetizes the animals, carefully removes their brains, firms the brains up with formalin, freezes them, then shaves them into slices thinner than a strand of human hair to study under a microscope. What Lambert’s rodent brain slices are revealing is nothing short of revolutionary, challenging the loud pundits and long-held cultural views that only mothers are wired for nurture. Lambert, one of a small but growing number of scientists who study the biology of father behavior, is finding that not just mothers experience surges of hormones associated with bonding and nurturing. The same hormones increase, though not to the same degree, in fathers. Rat mothers are not the only ones whose brains become sharper, making them more efficient foragers and more courageous and level-headed than females without offspring. Lambert has found that the same is true of fathers’ brains. Fatherhood makes the male California deer mouse smarter, too. © 1996-2013 The Washington Post
By Breanna Draxler Is it a coincidence that the word vole is an anagram of love? Probably so, but since prairie voles mate for life, they have since been designated as the unofficial species used to study monogamy in lab animals. And a new study finds that their rare partnerships are cemented by chemical changes on their genes, called epigenetic changes, that result from their sexual encounters. When a prairie vole (Microtus ochrogaster) finds a mate, the two form a strong bond. Not only do they stay together for life and share child care duties, but the lovers will guard their mates aggressively against voles of the opposite sex. Scientists knew from previous studies that this bonding was regulated by neurotransmitters—chemical communicators in the brain such as oxytocin, which is linked to sex and reproduction, and vasopressin, associated with social recognition. However researchers were unsure what the biological basis was for such a sharp behavioral shift after mating. To find out, scientists at Florida State University paired up virgin male and female voles and gave the couples a cage together for a number of hours. Some couples were allowed to mate while others were prevented from doing so. The non-mating female voles instead received drug injections in the nucleus accumbens, a part of the brain’s pleasure center. The drugs affected the voles’ epigenetics by unwinding their DNA so that genes for vasopressin and oxytocin receptors were more highly transcribed.
A patient at the Kwong Wah and Queen Elizabeth Hospitals discovered he was also a woman when he came for treatment for a swelling abdomen. Photo: Nora Tam A 66-year-old apparently male patient made a stunning discovery when he sought treatment for swelling in his abdomen. The swelling was a cyst on his ovary and he was in fact a woman. The condition was caused by a very rare combination of two genetic disorders. One, Turner syndrome, causes women to lack some female features, including the ability to get pregnant. Sufferers usually look like women, but in this case the patient also had congenital adrenal hyperplasia (CAH), which boosted the male hormones and made the patient look like a man. The case was reported by doctors from Kwong Wah Hospital and Queen Elizabeth Hospital, who treated the patient. It was published in the Hong Kong Medical Journal yesterday. "The patient, by definition, is a woman who cannot get pregnant. But she also has CAH, which gave her the appearance of a man," Chinese University paediatrics professor Ellis Hon Kam-lun said. "It's an interesting and very rare case of having the two combinations. It probably won't be seen again in the near future." The 66-year-old Vietnam-born Chinese man is an orphan. He has a beard, small penis and no testes. Just 1.37 metres tall, he has decided to continue perceiving himself as a male and may receive male hormone treatment, the report said. © 2013 South China Morning Post Publishers Ltd
By ANAHAD O'CONNOR The number of middle-aged men with prescriptions for testosterone is climbing rapidly, raising concerns that increasing numbers of men are abusing the powerful hormone to boost their libidos and feel younger, researchers reported on Monday. Testosterone replacement therapy is approved specifically for the treatment of abnormally low testosterone levels, a condition called hypogonadism. The hormone helps build muscle, reduce body fat and improve sex drive. But a study published in the journal JAMA Internal Medicine found that many men who get prescriptions for the hormone have no evidence of a deficiency at all. The new study is the largest of testosterone prescribing patterns to date, involving nearly 11 million men who were tracked through a large health insurer. The report showed that the number of older and middle-aged men prescribed the hormone has tripled since 2001. Men in their 40s represent the fastest-growing group of users. About half of men prescribed testosterone had a diagnosis of hypogonadism, and roughly 40 percent had erectile or sexual dysfunction. One third had a diagnosis of fatigue. The medical group that sets clinical guidelines for testosterone replacement therapy, the Endocrine Society, recommends treatment only in men who have unequivocally low testosterone levels. That finding requires a blood test. But the new report found that a quarter of men did not have their levels tested before they received the hormone. It was also unclear what proportion of men who did undergo testing actually had results showing a deficiency. Copyright 2013 The New York Times Company
Keyword: Hormones & Behavior
Link ID: 18228 - Posted: 06.04.2013
Zoe Cormier Love really does change your brain — at least, if you’re a prairie vole. Researchers have shown for the first time that the act of mating induces permanent chemical modifications in the chromosomes, affecting the expression of genes that regulate sexual and monogamous behaviour. The study is published today in Nature Neuroscience1. Prairie voles (Microtus ochrogaster) have long been of interest to neuroscientists and endocrinologists who study the social behaviour of animals, in part because this species forms monogamous pair bonds — essentially mating for life. The voles' pair bonding, sharing of parental roles and egalitarian nest building in couples makes them a good model for understanding the biology of monogamy and mating in humans. Previous studies have shown that the neurotransmitters oxytocin and vasopressin play a major part in inducing and regulating the formation of the pair bond. Monogamous prairie voles are known to have higher levels of receptors for these neurotransmitters than do voles who have yet to mate; and when otherwise promiscuous montane voles (M. montanus) are dosed with oxytocin and vasopressin, they adopt the monogamous behaviour of their prairie cousins. Because behaviour seemed to play an active part in changing the neurobiology of the animals, scientists suspected that epigenetic factors were involved. These are chemical modifications to the chromosomes that affect how genes are transcribed or suppressed, as opposed to changes in the gene sequences themselves. © 2013 Nature Publishing Group
By Scicurious Aging happens. As you get older, your body slows down, eventually your brain slows down, too. Some things go gradually, and some go suddenly. To many people, this might seem like a pretty random process. We used to think of aging this way, as just…well cells get old, which means we get old, too. DNA replication after a while starts making errors in repair, the errors build up, and on the whole body scale the whole thing just kind of goes downhill. It seems random. But in fact, it’s not. There are specific proteins which can help control this process. And one of these, NF-kB, in one particular brain region, may have a very important role indeed. NF-kB (which stands for nuclear factor kappa-light-chain-enhancer of activated B cells, which is why we use NF-kB) is a protein complex that has a lot of roles to play. It’s an important starting player in the immune system, where it helps to stimulate antibodies. It’s important in memory and stress responses. NF-kB is something called a transcription factor, which helps to control what DNA is transcribed to RNA, and therefore what proteins will eventually be produced. Transcription factors, as you can see, can have a very large number of functions. But in the hypothalamus, NF-kB may have the added function of helping to control aging. The hypothalamus is an area of many small nuclei (further sub areas of neurons) located at the base of the brain. It’s been coming more and more into vogue lately among neuroscientists. In the past, we were interested in the hypothalamus mostly for its role in controlling hormone release from the dangling pituitary gland before it, but now we are learning that the hypothalamus can play roles in fear, mood, food intake, reproduction, and now…aging. © 2013 Scientific American
Jo Marchant People with genes that make it tough for them to engage socially with others seem to be better than average at hypnotizing themselves. A study published today in Psychoneuroendocrinology1 concludes that such individuals are particularly good at becoming absorbed in their own internal world, and might also be more susceptible to other distortions of reality. Psychologist Richard Bryant of the University of New South Wales in Sydney and his colleagues tested the hypnotizability of volunteers with different forms of the receptor for oxytocin, a hormone that increases trust and social bonding. (Oxytocin's association with emotional attachment also earned it the nickname of 'love hormone'.) Those with gene variants linked to social detachment and autism were found to be most susceptible to hypnosis. Hypnosis has intrigued scientists since the nineteenth-century physician James Braid used it to alleviate pain in a variety of medical conditions, but it has never been fully understood. Hypnotized people can undergo a range of unusual experiences, including amnesia, anaesthesia and the loss of the ability to move their limbs. But some individuals are more affected by hypnosis than others — and no one knows why. Hormones and hypnotism How susceptible someone is to persuasion is an important factor in how easily they can be hypnotized by someone else. Bryant and his colleagues have previously shown that spraying a shot of oxytocin up people’s noses makes them more hypnotizable, and more likely to engage in potentially embarrassing activities such as swearing or dancing at a hypnotist’s suggestion. © 2013 Nature Publishing Group,
By Luciana Gravotta If cupid had studied neuroscience, he’d know to aim his arrows at the brain rather than the heart. Recent research suggests that for love to last, it’s best he dip those arrows in oxytocin. Although scientists have long known that this hormone is essential for monogamous rodents to stay true to their mates, and that it makes humans more trusting toward one another, they are now finding that it is also crucial to how we form and maintain romantic relationships. A handful of new studies show that oxytocin makes us more sympathetic, supportive and open with our feelings—all necessary for couples to celebrate not just one Valentine’s Day, but many. These findings have led some researchers to investigate whether oxytocin can be used in couple therapy. The first bit of evidence that points to oxytocin as nature’s love glue comes from researchers who measured the hormone in couples. Psychology professor Ruth Feldman at Bar-Ilan University in Israel, spent years studying oxytocin’s role in the mother–child bond and recently decided to dive into the uncharted waters of romantic bonds by comparing oxytocin levels in new lovers and singles. “The increase in oxytocin during the period of falling in love was the highest that we ever found,” she says of a study she and her colleagues published in Psychoneuroendocrinology. New lovers had double the amount Feldman usually sees in pregnant women. Oxytocin was also correlated with the longevity of a relationship. Couples with the highest levels were the ones still together six months later. They were also more attuned to each other than the low-oxytocin couples when Feldman asked them to talk about a shared positive experience. © 2013 Scientific American,
By Kate Clancy I tend to go to bed freezing, especially so in the winter, so I pile our flannel sheet, blanket, and down comforter over me when I settle in to sleep. A few times each menstrual cycle, clustered together in the luteal phase between ovulation and menses, I wake up from sleep completely soaked in my own sweat – not a delightful sight or experience. Usually I get up, change pajamas, and try to find a dry spot on the bed to go back to sleep (I promise the sheets eventually get washed, but I’m not about to wake my husband – and sometimes daughter – to change the bed at 3am). These night sweats started when I was still intensively breastfeeding my daughter and was marathon training, when she was under a year old. At first, I thought it was because we were co-sleeping and we slept next to each other. But I never experienced them next to my husband before that point, and he is a six foot four heat generating machine. When the marathon was over and I returned to less strenuous activity, breastfeeding frequency was also starting to decline. I didn’t get any night sweats again for quite some time. Then there was roller derby. At first, roller derby was a pastime, a recreational activity where I got to learn something totally new and hang out with women I respected. But of course, being the competitive person I am, it became an obsession, and in addition to roller derby practices I was working out quite a lot on my own time. Over the last year I’ve made additional nutritional adjustments to further improve my performance, and I’ve increased the intensity of my off-skates workouts. I work out a minimum of five hours a week, but in the middle of the season it is usually a minimum of nine hours per week. © 2012 Scientific American
Keyword: Hormones & Behavior
Link ID: 17609 - Posted: 12.17.2012
By GRETCHEN REYNOLDS Is playing football like falling in love? That question, which would perhaps not occur to most of us watching hours of the bruising game this holiday season, is the focus of a provocative and growing body of new science examining the role of oxytocin in competitive sports. Oxytocin is, famously, the “love hormone,” a brain peptide known to promote positive intersocial relations. It makes people like one another, especially in intimate relationships. New mothers are awash in oxytocin (which is involved in the labor process), and it is believed that the hormone promotes bonding between mother and infant. New-formed romantic couples also have augmented bloodstream levels of the peptide, many studies show. The original attraction between the lovers seems to prompt the release of oxytocin, and, in turn, its actions in the brain intensify and solidify the allure. Until recently, though, scientists had not considered whether a substance that promotes cuddliness and warm, intimate bonding might also play a role in competitive sports. But the idea makes sense, says Gert-Jan Pepping, a researcher at the Center for Human Movement Sciences at the University of Groningen in The Netherlands, and the author of a new review of oxytocin and competition. “Being part of a team involves emotions, as for instance when a team scores, and these emotions are associated with brain chemicals.” Copyright 2012 The New York Times Company
By Scicurious Last week, Sci covered a paper on the nematode “version” of oxytocin, nematocin, and its role in learning behavior. We usually think of oxytocin-like peptides (including oxytocin and vasopressin), as being linked with emotion, trust, love, and of course, sex. But oxytocin also tends to get a lot of hype, especially as the “love”‘ or “trust” hormone. But it’s not that. It’s much more complicated than that. And understanding the evolution of oxytocin, and its very long history, allows us to understand HOW much more complicated than that. Because while nematodes have an oxytocin-like molecule that has roles in learning behavior…well it also has roles in mating. But I wouldn’t go do far as to call nematocin (oxytocin + nematode = nematocin!) the nematode love drug. Unless, of course, you believe nematodes have deep, passionate, trusting, and communicative one-night worm stands which commence upon immediate contact and end immediately after. Hey, you never know. This happens to be an interesting issue of Science, in which TWO papers were published, both identifying nematocin, at the same time. As they both call the new molecule nematocin, I have hopes that the two groups were happily collaborating with each other to further the interests of science (though I know that many times, when two groups find the name new, hot thing, it’s often a very bitter race to publish). So what is nematocin? Nematocin appears to be a chemical closely related to oxytocin and vasopressin, those much vaunted chemical in mammals which are making so much press for their role in our emotions and moral behavior. But oxytocin and vasopressin are both more complicated than emotion. Vasopressin, for example, plays a role in water balance. And it appears that the newly discovered nematocin in the nematode C. elegans may be similar, with more than one role in more than one system. © 2012 Scientific American
By Laura Beil Kotex, the company that first capitalized on the concept of “feminine hygiene” more than 90 years ago, recently gained newfound success after it began targeting an underserved market: girls who start their periods before they start middle school. With hearts, swirls and sparkles, the U brand offers maxi pads and tampons for — OMG! — girls as young as 8, promoted through a neon-hued website with chatty girl-to-girl messages and breezy videos. “When I had my first period I was prepared,” reads one testimonial. “It was the summer before 4th grade….” Today it has become common for girls to enter puberty before discovering Are You There God? It’s Me, Margaret. Over the second half of the 20th century, the average age for girls to begin breast development has dropped by a year or more in the industrialized world. And the age of first menstruation, generally around 12, has advanced by a matter of months. Hispanic and black girls may be experiencing an age shift much more pronounced. The idea of an entire generation maturing faster once had a strong cadre of doubters. In fact, after one of the first studies to warn of earlier puberty in American girls was published in 1997, skeptics complained in the journal Pediatrics that “many of us in the field of pediatric endocrinology believe that it is premature to conclude that the normal age of puberty is occurring earlier.” Today, more than 15 years later, a majority of doctors appear to have come around to the idea. Have a conversation with a pediatric endocrinologist, and it isn’t long before you hear the phrase “new normal.” © Society for Science & the Public 2000 - 2012
By Melissa Healy, Los Angeles Times If retired Army Gen. David H. Petraeus had gotten an occasional dose of supplemental oxytocin, a brain chemical known to promote trust and bonding, he might still be director of the Central Intelligence Agency, new research suggests. A study published Tuesday in the Journal of Neuroscience has uncovered a surprising new property of oxytocin, finding that when men in monogamous relationships got a sniff of the stuff, they subsequently put a little extra space between themselves and an attractive woman they'd just met. Oxytocin didn't have the same effect on single heterosexual men, who comfortably parked themselves between 21 and 24 inches from the comely female stranger. The men who declared themselves in "stable, monogamous" relationships and got a dose of the hormone chose to stand, on average, about 6 1/2 inches farther away. When researchers conducted the experiment with a placebo, they found no differences in the distance that attached and unattached men maintained from a woman they had just met. Even when an attractive woman was portrayed only in a photograph, the monogamous men who received oxytocin put a bit more distance between themselves and her likeness. But when the new acquaintance was a man, administration of oxytocin did not prompt attached men to stand farther away than single men, the researchers reported. Los Angeles Times, Copyright 2012
by Andy Coghlan Men with partners increase the space they feel comfortable with between themselves and an attractive woman if exposed to the bonding hormone oxytocin. René Hurlemann at the University of Bonn in Germany and colleagues gave men either a sniff of oxytocin or a placebo before asking them to choose the ideal distance for an interaction with a woman. The distance that they felt was comfortable significantly increased after sniffing oxytocin, but only for men in relationships. The team conclude that oxytocin discourages partnered but not single men from getting close to a female stranger. Journal reference: Journal of Neuroscience, DOI: 10.1523/jneurosci.2755-12.2012 © Copyright Reed Business Information Ltd.
by Shaoni Bhattacharya Talk about having your cake and eating it. Fasting might not be the only route to a longer life – a hormone seems to work just as well, for mice at least. We know that some animals can extend their lifespan by consuming fewer calories. Engineered mice can get the same effect by simply pumping out high levels of a hormone normally produced during a fast, according to Steven Kliewer and David Mangelsdorf at the University of Texas Southwestern Medical Center in Dallas. Their team found that mice engineered to make higher levels of the hormone, FGF21, increased their lifespan on average by over a third. "What we are seeing is the benefit of caloric restriction without having to diet," he says. Humans have the hormone too, and Kliewer believes FGF21 has the potential to extend the human "health-span" – the time we live healthy lives. The researchers believe FGF21 may act to prolong life by affecting pathways such as the insulin-like growth factor-1 (IGF-1) pathway implicated in ageing. "It blocks growth hormones promoting pathways which are associated with diseases, including cancers and metabolic diseases, and as a consequence these animals live longer," says Kliewer. © Copyright Reed Business Information Ltd.
Researchers in the U.S. have found signs of puberty in American boys up to two years earlier than previously reported — age nine on average for blacks, 10 for whites and Hispanics. Other studies have suggested that girls, too, are entering puberty younger. Why is this happening? Theories range from higher levels of obesity and inactivity to chemicals in food and water, all of which might interfere with normal hormone production. But those are just theories, and they remain unproven. Doctors say earlier puberty is not necessarily cause for concern. And some experts question whether the trend is even real. Boys are more likely than girls to have an underlying physical cause for early puberty.Boys are more likely than girls to have an underlying physical cause for early puberty. (Jennifer DeMonte/Associated Press) Dr. William Adelman, an adolescent medicine specialist in the Baltimore area, says the new research is the first to find early, strong physical evidence that boys are maturing earlier. But he added that the study still isn't proof and said it raises a lot of questions. Earlier research based on 20-year-old national data also suggested a trend toward early puberty in boys, but it was based on less rigorous information. The new study involved testes measurements in more than 4,000 boys. Enlargement of testes is generally the earliest sign of puberty in boys. The study was published online Saturday in Pediatrics to coincide with the American Academy of Pediatrics' national conference in New Orleans. © CBC 2012
By Marcia Malory Ask this question, and you will probably receive one of two responses: Yes. People choose to be gay. They are making an immoral choice, which government should discourage. Or No. Sexual preference is biologically determined. Government should protect gay people from discrimination because homosexuality is an unalterable aspect of their identity. These two answers have something in common: With both of them, the science conveniently supports the moral decision. What if neither answer is right? Perhaps sexual preference can be changed – and people have the right to engage in gay sex and have homosexual relationships if they choose to do so. (The fourth option, that gay people have no choice but to be gay, but should be punished for it anyway, is morally unthinkable.) What does science tell us about sexual preference? We know, from many twin and adoption studies, that sexual preference has a genetic component. A gay man is more likely than a straight man to have a (biological) gay brother; lesbians are more likely than straight women to have gay sisters. In 1993, a study published in the journal Science showed that families with two homosexual brothers were very likely to have certain genetic markers on a region of the X chromosome known as Xq28. This led to media headlines about the possibility of the existence of a “gay gene” and discussions about the ethics of aborting a “gay” fetus. © 2012 Scientific American,
By Tina Hesman Saey New work suggests that a hormone that makes the body think it’s starving could prolong life about as long as severely cutting calories does but without the denial. A hormone called fibroblast growth factor-21, or FGF21, lengthened the lives of mice that had been genetically engineered to constantly produce large amounts of the protein, researchers at the University of Texas Southwestern Medical Center at Dallas report online October 15 in eLife. The hormone is normally made by the liver during fasting and may tap into some of the same life-extending biochemical processes as does caloric restriction, a proven longevity booster. Caloric restriction — usually defined as cutting calorie intake to 75 to 80 percent of the amount needed to maintain normal body weight, while still maintaining good nutrition — has been shown lengthen life in a wide variety of species, such as fruit flies and dogs. Minimal calorie consumption turns on many different biological processes that slow aging, says Cynthia Kenyon, a developmental biologist at the University of California, San Francisco. The hormone in the study somehow interferes with a chain reaction anchored by insulin-like growth factor-1 (IGF-1), a process that is also shut down by caloric restriction and thought to be responsible for many of its life-extending effects. In the study, researchers led by UT Southwestern’s David Mangelsdorf and Steven Kliewer genetically engineered mice to constantly make five to 10 times as much FGF21 as normal. These engineered mice lived 30 to 40 percent longer than normal mice on a standard diet. Female mice benefitted from the hormone even more than males; about a third of the FGF21-producing female mice still were alive at 44 months old. Average survival for normal mice in the study was about 28 months. © Society for Science & the Public 2000 - 2012
By Gary Stix First off, this study on a molecule tied to social interaction was conducted in animals. So I’m supposed to turn on the siren and the flashing red light here to let you know that the headline you just read might not apply in humans. Still, the animals in question, prairie voles, are a special case, models of faithfulness that put humans to shame when it comes to the delicate topic of monogamy. Once hitched, the rodents stick with their mates for life—an example of moral pulchritude in the animal kingdom that many of us human sinners can never hope to emulate. It could easily become the state animal for whole regions of the U.S. For just that alone, the implications of the experiment in question are particularly intriguing. The new research shows that oxytocin, the bonding hormone, is sometimes capable of turning the upstanding rodent into an anti-social lout, making the study results more compelling in many ways than if they were reported in errant humans. So the man-bites-dog headline stays. This all came up when Karen Bales, a professor at University of California, Davis, wanted to know what would happen if oxytocin gets administered for lengthy intervals, not the short-term dosing that has occurred in the multitude of previous vole studies that linked the hormone to monogamous behavior. In their experiment, Bales and team gave either a low, medium or high dose through the nose to 29 voles, and a saline solution to 14 controls At first, the animals became all cuddly as in previous studies But after three weeks, an entire vole childhood (from weaning to sexual maturity), they started breaking bad. Males did not engage in the normal behavior of “pair bonding,” that drives them to look for the girl of their dreams. And female voles’ natural mothering instinct seemed to disappear: when placed nearby young pups that were not their own, they didn’t dote, as they are wont to do. The cuddle hormone had turned the rodents into meanies. © 2012 Scientific American