Links for Keyword: Hormones & Behavior

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Content provided by AFP High estrogen levels in women while they are ovulating may be directly responsible for sluggishness or problems concentrating, a Canadian study released Friday has found. Researchers at Concordia University's Center for Studies in Behavioral Neurobiology in Montreal linked high estrogen levels in laboratory rats to an inability to pay attention and learn. These high levels have also been shown to interfere with women's ability to pay attention, but the study, to be published in the journal Brain and Cognition, is the first to show "how this impediment can be due to a direct effect of the hormone on mature brain structures," said a statement. Both humans and rodents have similar brain physiology. "Although estrogen is known to play a significant role in learning and memory, there has been no clear consensus on its effect," said study lead author Wayne Brake. "Our findings...show conclusively that high estrogen levels inhibit the cognitive ability in female rodents." Researchers repeatedly exposed rats to a tone, with no consequences. Once they became used to it and ignored it, another stimulus was linked to the tone. © 2010 Discovery Communications, LLC.

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory and Learning
Link ID: 14501 - Posted: 09.28.2010

Big deal went sour? Blame the testosterone

Tim Kiladze A chief executive officer’s patience and co-operation can make or break a corporate merger or acquisition. That’s no secret. But researchers at the University of British Columbia’s Sauder School of Business now offer a biological explanation for male CEOs’ willingness, or lack thereof, to negotiate: testosterone levels. The UBC team crunched the numbers for 350 corporate deals completed between 1997 and 2007 and determined that the aggression-causing hormone directly affects a male CEO’s tendency to bid for a company – and to walk away from an unfavourable deal. “Normally, assets should go to buyers that value [them] the most,” finance professor and lead researcher Maurice Levi said, “if decisions are based purely on the basis of rationality.” However, his team found that hormones intervene and make CEOs bid for things they don’t necessarily need, or turn down offers out-of-hand, without trying to negotiate better terms. “They might be pursuing things that give them the most dominance, but do not give them the most value,” Mr. Levi said. Notably, men with higher testosterone levels are 20 per cent more likely to walk away from a takeover offer. They are also 4 per cent more likely to make takeover bids, a small effect but still statistically significant. The Sauder study was based on a 2007 Harvard University experiment in which pairs of male participants tried to make a deal to split $40. Participants with above-average testosterone levels, tested in a laboratory, were more likely to reject a lowball offer, whereas those with below-average levels were less likely to drive a hard bargain. © Copyright 2010 CTVglobemedia Publishing Inc.

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 14449 - Posted: 09.14.2010

Receipts a large — and largely ignored — source of BPA

By Janet Raloff Cash register and other receipts may expose consumers to substantial amounts of bisphenol A, a hormone-mimicking chemical that has been linked with a host of potential health risks, according to a trio of recent studies. Each study offers preliminary evidence that a large number of retail outlets print sales receipts on certain types of heat-sensitive, or thermal, paper that use BPA as a color developer. Two of the new studies also showed that the BPA coating easily rubs off onto fingers. And one found evidence that BPA from receipts may penetrate skin. The pollutant, which mimics the biological activity of estrogen, has been tied to health risks from behavioral problems in children to obesity and heart ailments. In animals, exposures in the womb put moms and their offspring at risk for later metabolic diseases. Based on growing concern about possible risks from ubiquitous exposure to BPA, especially in children, the federal government recently issued warnings to parents about where their families were most likely to encounter the chemicals. Store receipts did not make the list, although there have been hints for years that thermal receipt paper could be a rich source. Chemist John Warner learned about the chemistry of thermal- and pressure-sensitive papers while working for Polaroid years ago. Manufacturers lay a powdery coating containing BPA, a dye and a solvent onto one side of a piece of paper. When heat or pressure is applied, the coating’s constituents merge to release the ink’s color, he explains. © Society for Science & the Public 2000 - 2010

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 14321 - Posted: 08.05.2010

The Anti-Lesbian Drug

Genetic engineers, move over: the latest scheme for creating children to a parent’s specifications requires no DNA tinkering, but merely giving mom a steroid while she’s pregnant, and presto—no chance that her daughters will be lesbians or (worse?) ‘uppity.’ Or so one might guess from the storm brewing over the prenatal use of that steroid, called dexamethasone. In February, bioethicist Alice Dreger of Northwestern University and two colleagues blew the whistle on the controversial practice of giving pregnant women dexamethasone to keep the female fetuses they are carrying from developing ambiguous genitalia. (That can happen to girls who have congenital adrenal hyperplasia (CAH), a genetic disorder in which unusually high prenatal exposure to masculinizing hormones called androgens can cause girls to develop a deep voice, facial hair, and masculine-looking genitalia.) The response Dreger got from physicians and scientists who were outraged over this unapproved use of dexamethasone caused her to dig deeper into the scientific papers of the researcher who has promoted it. The result of that digging is a discovery that is much less outrageous than the PR push, and some media coverage, would have you believe, but one that nonetheless raises important questions about gender, sexuality, and research on unknowing patients. In an essay titled “Preventing Homosexuality (and Uppity Women) in the Womb?” and posted on the bioethics forum of The Hastings Center, a think tank in Garrison, N.Y., Dreger and her colleagues pluck numerous brow-raising statements from the writings of pediatric endocrinologist Maria New of Mount Sinai Medical Center in New York, who has long promoted prenatal dexamethasone to treat CAH. But if that position is controversial (as I’ll explain below), what Dreger and her colleagues claim to have uncovered is even more so. New, they say, wants to use dexamethasone to prevent CAH girls from becoming lesbians, from rejecting motherhood, and from choosing traditionally masculine careers. © 2010 Newsweek, Inc

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 14229 - Posted: 07.06.2010

She Doesn’t Trust You? Blame the Testosterone

By NICHOLAS WADE The glue that binds a human society together is trust. But people who trust others too much are likely to get taken for a ride. Both trust and distrust, it now seems, are influenced by hormones that can induce people to ratchet their feeling of trust up or down. The trust side of the equation is mediated by a brain hormone known as oxytocin. A soft touch or caress will send a pulse of oxytocin into a person’s bloodstream. Swiss researchers found in 2005 that a squirt of oxytocin would make players in an investment game more willing to hand over their money to strangers. It may seem strange that there is a hormonal influence in such a delicate calculation as to whether or not to trust someone. But perhaps trust is so important to a society’s survival that natural selection has generated a hormonal basis for it. In any event, trust has a downside — one may hand over too much money to a Mr. Madoff who promises to generate steady returns in both up and down markets. There needs to be an antidote to oxytocin that makes a person keep those warm, fuzzy feelings suppressed in the appropriate circumstances. Researchers at Utrecht University in Holland now report that they have identified this antidote: it is testosterone. They gave young women a dose of the hormone in the form of a drop of liquid placed under the tongue, then asked them to judge the trustworthiness of a series of men’s faces shown in photographs. The women were significantly less inclined to trust a face when given testosterone than when they had taken a placebo, the Dutch team reported last month in The Proceedings of the National Academy of Sciences. Copyright 2010 The New York Times Company

Related chapters from BN: Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 14161 - Posted: 06.24.2010

PMS’s Flip Side

Many women say their moods follow a monthly cycle. Now brain researchers have scientific evidence that women's hormonal changes affect the reward circuits -- areas of the brain that produce feelings of pleasure. "No one had ever actually imaged the reward system of the brain during the menstrual cycle," says Karen Berman, who led the research at the National Institute of Mental Health. "This is a very fundamental part of our brain that has great evolutionary significance because it helps us to find out what in the environment is important for us to pay attention to for survival," she explains. "We thought this would be a very important brain network to study because people who have mood disorders, women who have menstrually related mood problems likely aren't activating and processing with this system in a normal fashion." Berman and her team used functional MRI to image women's brains at two key points in their cycle -- before ovulation when the hormone estrogen increases, and after ovulation when the hormone progesterone dominates. The volunteers played a slot-machine game to win money, activating the brain's reward systems. © ScienCentral, 2000-2007.

Related chapters from BN: Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 10075 - Posted: 06.24.2010

Brain’s Reward Circuit Activity Ebbs and Flows with a Woman’s Hormonal Cycle

Fluctuations in sex hormone levels during women’s menstrual cycles affect the responsiveness of their brains’ reward circuitry, an imaging study at the National Institute of Mental Health (NIMH), a component of the National Institutes of Health (NIH), has revealed. While women were winning rewards, their circuitry was more active if they were in a menstrual phase preceding ovulation and dominated by estrogen, compared to a phase when estrogen and progesterone are present. “These first pictures of sex hormones influencing reward-evoked brain activity in humans may provide insights into menstrual-related mood disorders, women’s higher rates of mood and anxiety disorders, and their later onset and less severe course in schizophrenia,” said Karen Berman, M.D., chief of the NIMH Section on Integrative Neuroimaging. “The study may also shed light on why women are more vulnerable to addictive drugs during the pre-ovulation phase of the cycle.” Berman, Drs. Jean-Claude Dreher, Peter Schmidt and colleagues in the NIMH Intramural Research Program report on their functional magnetic resonance imaging (fMRI) study online during the week of January 29, 2007 in the Proceedings of the National Academy of Sciences. Reward system circuitry includes: the prefrontal cortex, seat of thinking and planning; the amygdala, a fear center; the hippocampus, a learning and memory hub; and the striatum, which relays signals from these areas to the cortex. Reward circuit neurons harbor receptors for estrogen and progesterone. However, how these hormones influence reward circuit activity in humans has remained unclear.

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 3: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 9917 - Posted: 06.24.2010

In Raising the World’s I.Q., the Secret’s in the Salt

By DONALD G. McNEIL Jr. ASTANA, Kazakhstan — Valentina Sivryukova knew her public service messages were hitting the mark when she heard how one Kazakh schoolboy called another stupid. “What are you,” he sneered, “iodine-deficient or something?” Ms. Sivryukova, president of the national confederation of Kazakh charities, was delighted. It meant that the years spent trying to raise public awareness that iodized salt prevents brain damage in infants were working. If the campaign bore fruit, Kazakhstan’s national I.Q. would be safeguarded. In fact, Kazakhstan has become an example of how even a vast and still-developing nation like this Central Asian country can achieve a remarkable public health success. In 1999, only 29 percent of its households were using iodized salt. Now, 94 percent are. Next year, the United Nations is expected to certify it officially free of iodine deficiency disorders. That turnabout was not easy. The Kazakh campaign had to overcome widespread suspicion of iodization, common in many places, even though putting iodine in salt, public health experts say, may be the simplest and most cost-effective health measure in the world. Each ton of salt needs about two ounces of potassium iodate, which costs about $1.15. Copyright 2006 The New York Times Company

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 1: Introduction: Scope and Outlook
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 20:
Link ID: 9757 - Posted: 06.24.2010

A Battle Over �Juice of Youth’

By ABBY ELLIN IT’S almost impossible to turn on the television and not glimpse Suzanne Somers smiling back at you. In the last week, she has appeared on the “Today” show, “The View” and “Entertainment Tonight.” She has chatted with Martha Stewart and bonded with Bill O’Reilly. She is not discussing the war in Iraq, nor offering opinions on the Mark Foley scandal. Her latest book, “Ageless: The Naked Truth About Bioidentical Hormones,” hit stores on Oct. 10, and Ms. Somers is simply doing what celebrities do these days: selling. She happens to be good at it. The actress made the ThighMaster a household product and, of the 13 books she has written, 7 have been best sellers. If history — and a good marketing plan — has anything to do with it, “Ageless” may just be her eighth. It is a paean to bioidentical hormone replacement therapy, a controversial treatment for menopausal women that she dubs “the juice of youth.” “I had bone loss 10 years ago — I restored it with bioidenticals,” Ms. Somers, who turns 60 on Monday, said in a telephone interview from Houston, where she was speaking before a group of 1,100 pharmacists. They also recharged her libido, she said, reduced her depression, and rejuvenated her hair, skin and body. (In February 2001, National Enquirer photographed her leaving a plastic surgery clinic, and she subsequently admitted to having had liposuction on her upper back and hips.) The book, though, has raised the hormone levels of at least seven medical doctors. The doctors — three of whom are quoted in the book — generally support the concept of bioidentical hormone therapies but say that too little research has been done to assure that they are safe. Copyright 2006 The New York Times Company

Mommy’s Brain

We all know motherhood changes the body. But research in animals shows it also changes the brain. As this ScienCentral News video explains, parenting seems to enhance learning and memory in both moms and dads. Coping day or night with the demands of a new born baby and worrying over every cough and sniffle are just in a day's work for parents, but it's something that people without kids often find hard to imagine being able to do� until they have kids of their own that is. So where do that cool head, that parenting instinct and those coping skills just materialize from? Sleep-deprived new mothers might find it hard to believe, but having kids may actually make you sharper. Brain researcher Kelly Lambert says that, at least in rodents, pregnancy and parenting change the brain and behavior in ways that go beyond nursing and nurturing. "From what we've seen, having a whole different being to take care of requires a whole new set of skills and a lot more awareness, cognitive awareness and multi-tasking," explains Lambert, professor and Chair of the psychology department at Randolph-Macon College. © ScienCentral, 2000-2006.

Brain �buffer’ may control premenstrual moods

An emotional buffer zone in the brain may not be working as it should in women who experience premenstrual moodiness, a new study suggests. David Silbersweig and colleagues at the Weill Medical College of Cornell University, New York, US, used functional magnetic resonance imaging to scan the brains of 12 women whose moods remained steady throughout their menstrual cycles. From 1 to 5 days before menstruation, and 8 to 12 days after, the women’s brains were scanned as they were shown printed words with either negative, neutral, or positive connotations – words like “rape”, “cancer”, “bookcase”, “rotate”, “gentle” and “delighted” – to engage the emotion-processing part of the brain. At the same time, the women were motivated to complete a simple cognitive task. The scans showed that the orbitofrontal cortex – part of the brain involved in controlling emotions and regulating motivation – was more active during the task in the days before menstruation. After menstruation, that part of the brain was relatively inactive during the task. Silbersweig says that the difference in brain activity may “buffer” hormonal changes in these women, helping them to maintain a consistent emotional state. “Because this area is kicking in, these women are able to avoid moodiness,” he says. © Copyright Reed Business Information Ltd.

Trust me, I’m spraying you with hormones

Giving people a whiff of a key chemical can make them more inclined to trust strangers with their cash, a new study reveals. Just three puffs of a nasal spray containing a hormone called oxytocin increased the chance that people would part with their money. The research centred around a game in which an “investor” player gives part or all of his money on blind trust to an anonymous “trustee” player who earns interest on the combination of his own money and the invested sum. But the investor is told there is no obligation for the “trustee” to give any money back at all - they risk losing any money they choose to invest. Michael Kosfeld at the University of Zurich, Switzerland, who led the study found that investors gave away their money far more willingly if they had sniffed oxytocin than if they had sniffed a placebo. But this extra willingness disappeared when the trustee’s role was computerised, rather than carried out by another human, confirming that the effect was interpersonal, and not simply a general willingness to gamble. Kosfeld speculates that the hormone reduces people’s aversion to betrayal, overcoming an unwillingness to initiate interaction with strangers. This matches observations in animal studies. “It helps animals to approach one another, which is a parallel with trust in our game,” he says. © Copyright Reed Business Information Ltd.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 7427 - Posted: 06.24.2010

Testosterone’s Sidekick

Hormones have long been considered the solo act that molds brains along gender lines. But in recent years, hints that certain genes on the sex chromosomes might also play a role have been emerging. Now, new research points to the first structural brain difference between male and female mammals attributed to genetics alone. Sex hormones, in particular testosterone, help shape the developing brain of fetuses and newborns. Testosterone, secreted by the gonads, makes male brains distinct from female ones, and it is thought to account for difference in behavior and brain structure. A group of scientists, though, has wondered for years whether genes on the X and Y chromosomes have a hand in shaping brain differences. To find out, neuroendocrinologist Arthur Arnold at the University of California, Los Angeles, collaborated with colleagues in the United Kingdom who had genetically altered mice. Robin Lovell-Badge and Paul Burgoyne, developmental geneticists at the Medical Research Council’s National Institute for Medical Research in London, performed a genetic sex change. By using mice with a deletion in their Y chromosome for a gene called Sry, which kick-starts testes development, they ended up with XY “females” that had ovaries; adding Sry to the genomes of females generated XX "males" with testes. Although these mice had fully developed sex organs, both groups had fertility problems due to the gene manipulations. Copyright © 2002 by the American Association for the Advancement of Science.

Testosterone aids older men’s brains, UCSF study says

Older men with higher testosterone levels performed better on tests of cognition in a new study from UCSF researchers. The study suggests that older men who are prescribed testosterone supplements may reduce their risk of cognitive decline, a precursor state to Alzheimer’s disease, the researchers said. Men’s bodies tend to produce less testosterone as they age, and some doctors have begun prescribing supplements of the hormone to increase libido and treat other age-related problems in men. “The men in the study with higher levels of bioavailable testosterone, the testosterone that can reach the brain, did significantly better on these cognitive tests than men with lower levels,” said lead author Kristine Yaffe, MD, UCSF assistant professor of psychiatry, neurology and epidemiology and biostatistics, and chief of geriatric psychiatry at SFVAMC.

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 4: Development of the Brain
Link ID: 1882 - Posted: 06.24.2010

Early programming of the hypothalamo–pituitary–adrenal axis

Stephen G. Matthews stephen.matthews@utoronto.ca Trends in Endocrinology and Metabolism 2002, 13:373-380 The ability of the early environment to program the hypothalamo–pituitary–adrenal (HPA) axis has been documented in several species. There is considerable evidence that a similar process can also occur in humans. Studies of animals indicate that the phenotype of HPA function following early manipulation depends on the timing and intensity of the manipulation, in addition to the gender of the fetus or neonate. There is considerable interplay between the HPA and the hypothalamo–pituitary–gonadal axes, and emerging evidence indicates that this interaction is modified by early environmental manipulation. Studies are rapidly unraveling the mechanisms that underlie developmental programming of the HPA axis. Understanding these mechanisms could hold the key to the development of therapeutic interventions aimed at reversing the impact of an adverse intrauterine or neonatal environment. © Elsevier Science Limited 2002

The Estrogen Dilemma

By CYNTHIA GORNEY Here we are, two fast-talking women on estrogen, staring at a wall of live mitochondria from the brain of a rat. Mitochondria are cellular energy generators of unfathomably tiny size, but these are vivid and big because they were hit with dye in a petri dish and enlarged for projection purposes. They’re winking and zooming, like shooting stars. “Oh, my God,” Roberta Diaz Brinton said. “Look at that one. I love these. I love shooting mitochondria.” Brinton is a brain scientist. Estrogen, particularly in its relationship to the health of the brain, is her obsession. At present it is mine too, but for more selfish reasons. We’re inside a darkened lab room in a research facility at the University of Southern California, where Brinton works. We are both in our 50s. I use estrogen, by means of a small oval patch that adheres to my skin, because of something that began happening to me nine years ago — to my brain, as a matter of fact. Brinton uses estrogen and spends her work hours experimenting with it because of her own brain and also that of a woman whose name, Brinton will say, was Dr. A. She’s dead now, this Dr. A. But during the closing years of her life she had Alzheimer’s, and Brinton would visit her in the hospital. Dr. A. was a distinguished psychotherapist and had vivid stories she could still call to mind about her years in Vienna amid the great European psychologists. “We’d spend hours, me listening to her stories, and I’d walk out of the room,” Brinton told me. “Thirty seconds later, I’d walk back in. I’d say, ‘Dr. A., do you remember me?’ And she was so lovely. She’d say: ‘I’m so sorry. Should I?’ ” The problem with the estrogen question in the year 2010 is that you set out one day to ask it in what sounds like a straightforward way — Yes or no? Do I or do I not go on sticking these patches on my back? Copyright 2010 The New York Times Company

Bumpology: Is my baby making me forgetful?

by Linda Geddes The first indication that something might be up came when I caught myself asking my friend how she was feeling twice in the space of 30 seconds. Then I got into my car and couldn't find my keys, until a helpful passer-by pointed out that they were sitting in the lock outside. Since then, I've caught myself losing track of what I'm saying mid-sentence, and walking upstairs only to realise that I have no recollection of what I've gone up there for. It seems that "mumnesia", the forgetfulness that is said to beset pregnant women, may finally be taking hold. There have been plenty of studies supporting the idea that mumnesia exists – although some others have contradicted them. But a new study casts fresh light on exactly how pregnancy might interfere with memory in women, as well as exploring how long the effects last. It is also one of the largest studies looking into pregnancy and memory to have been conducted so far. Laura Glynn at the University of California, Irvine, asked 254 pregnant women to perform a series of memory tests at different stages of their pregnancy, as well as 12 to 14 weeks after the birth. She also measured levels of the hormones oestrogen and cortisol in their blood, and repeated these tests on 48 non-pregnant women. © Copyright Reed Business Information Ltd.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory and Learning
Link ID: 14136 - Posted: 06.24.2010

Caring grandmas explain evolutionary role of menopause

Debora MacKenzie The menopause may be an ordeal for women experiencing a 'hot flash', but new research suggests it had a good evolutionary cause – freeing women to be good grandmothers. Data from Africa indicates that the menopause creates grandmothers without young children of their own that can improve the survival chances of their daughters' offspring. Human female reproductive functions stop around age 50, and start tapering off even earlier. In other mammals, female reproduction simply stops because of ageing, at a variety of ages. But in humans the shutdown is deliberate and early. And it is genetically controlled, meaning the genes responsible were selected by evolution. However, since winning at evolution equals reproductive success, scientists have puzzled over what advantage giving up reproducing could have. Two hypotheses have been proposed: the first is that the difficulty of human childbirth is more likely to kill older women, so a woman who stops getting pregnant at 50 will still have time to raise her last child. The second is that the process allows a woman to help take care of her grandchildren – who she knows are carrying her genes. © Copyright Reed Business Information Ltd

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 10756 - Posted: 06.24.2010

Maternal hormone protects baby's brain during birth

Roxanne Khamsi The massive surge in the maternal hormone oxytocin that occurs during delivery might help protect newborns against brain damage, a new study in rats suggests. Researchers say the findings should encourage scientists to investigate whether elective caesarean sections, which lack this oxytocin surge, disrupt normal brain development. Yehezkel Ben-Ari, a neuroscientist at the Mediterranean Institute of Neurobiology in Marseille, France, and colleagues compared brain tissue samples from rat pups born naturally or by caesarean section. Brain cells from the naturally born pups did not fire in response to the nerve signalling chemical GABA, the researchers found. By comparison, at least 50% of the sampled cells from rats delivered by caesareans responded to the GABA signals. When the team gave pregnant rats atosiban – a drug that specifically blocks oxytocin’s effects – the brain cells from these rats were easily excited by GABA. This revealed that oxytocin was the hormone that made neurons from naturally delivered pups less receptive to GABA. © Copyright Reed Business Information Ltd.

Like mother, like cubs

Among spotted hyenas, being a supermom is less about packing lunches, and more about packing a hormonal punch that gives her cubs a powerful head start. In a study appearing in the April 26 edition of the international science journal Nature, Michigan State University zoology professor Kay Holekamp and her former graduate student Stephanie Dloniak along with Jeffrey French from the University of Nebraska, report that high-ranking, dominant spotted hyena mothers pass to their offspring high levels of certain hormones that make cubs more aggressive and sexually vigorous – in other words more likely to survive, thrive and reproduce. The study shows that alpha females have higher levels of androgen during the final stages of pregnancy than lower-ranking group members. “What this means is that there are gifts a mom can give to her baby,” said Holekamp, who also is a recent recipient of a 2006 Guggenheim Fellowship for her work on hyenas. “She can manipulate her offspring’s behavior and help her kids to survive and reproduce successfully by transferring status-related traits via prenatal hormone exposure.” “This research sheds light on mammalian reproductive biology and helps us imagine how evolution might have produced such a bizarre product,” Holekamp said © 2006 Michigan State University Division of University Relations

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 8839 - Posted: 06.24.2010

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