1. Study suggests oxytocin helps the brain to modulate social signals

    February 4, 2018 by Ashley

    From the Harvard University press release:

    Between sights, sounds, smells and other senses, the brain is flooded with stimuli on a moment-to-moment basis. How can it sort through the flood of information to decide what is important and what can be relegated to the background?

    Part of the answer, says Catherine Dulac, the Higgins Professor of Molecular and Cellular Biology, may lie with oxytocin.

    Though popularly known as the “love hormone,” Dulac and a team of researchers found evidence that oxytocin actually plays a crucial role in helping the brain process a wide array of social signals. The study is described in a December 12 paper published in eLife.

    The study, Dulac said, suggests that oxytocin acts like a modulator in the brain, turning up the volume of certain stimuli while turning others down, helping the brain to make sense of the barrage for information it receives from one moment to the next.

    In investigating the role of oxytocin in processing social signals, Dulac and colleagues began with an oft-observed behavior — the preference for male mice to interact with females.

    Studies have shown that this behavior isn’t just social — it’s actually hard-wired in the brains of male mice.

    When male mice are exposed to pheromone signals of females, Dulac and colleagues found, neurons in their medial amygdala showed increased levels of activation. When the same mice were exposed to pheromones of other males, those same neurons showed relatively little stimulation.

    Armed with that data, Dulac and colleagues targeted the gene responsible for producing oxytocin — which was known to be involved in social interactions ranging from infant/parent bonding to monogamy in certain rodents.

    Using genetic tools, researchers switched the gene off, and were surprised to find that both males’ preference for interacting with females and the neural signal in the amygdala disappeared.

    “This is a molecule that’s involved in the processing of social signals,” Dulac said. “We also showed, using pharmacology and genetics, that the effect happens on a moment-to-moment basis.

    “What we are trying to do is understand the logic of social interactions in one particular species,” she said. “What this study says is, for this particular type of social interaction, oxytocin plays a role, and that role is both at the level of the brain and the behavior.”

    Understanding oxytocin — and molecules like it — might shed light on a number of brain disorders.

    With an understanding of how various neurotransmitters work to amplify or quiet certain stimuli, Dulac said, researchers may gain new insight into how to treat everything from depression, which is often characterized by a lack of interest in social interactions, to autism, which is thought to be connected to an inability to sort through social and sensory stimuli.

    Ultimately, Dulac said, the study offers a small glimpse into what could be a larger system of molecules which act like modulators in the brain, turning certain stimuli up or down depending on the situation.

    “There may be many different regulators,” Dulac said. “Oxytocin might be one of a whole realm of modulators, each of which are important in a particular circumstance. That therefore gives the animal a great deal of plasticity in terms of engaging in a particular behavior, so it’s not the case that each time the animal encounters a particular stimulus it will react in exactly the same way. Depending on the state of the brain and the release of these neurotransmitters, the animal can boost its behavior toward the stimulus or ignore it.”


  2. Study suggests pregnant women with PTSD have higher levels of stress hormone cortisol

    December 14, 2017 by Ashley

    From the University of Michigan press release:

    Research has shown that a woman’s emotional and physical health during pregnancy impacts a developing fetus. However, less is known about the effect of past stressors and posttraumatic stress disorder on an expectant woman.

    To that end, researchers at the University of Michigan measured the stress hormone cortisol in pregnant women from early pregnancy to when their baby was 6 weeks old. They found that those with a dissociative type of PTSD that’s often related to childhood abuse or trauma had levels up to 10 times higher than their peers.

    These toxic levels of cortisol may contribute to health problems in the next generation, said Julia Seng, professor of nursing and lead author on the study.

    “We know from research on the developmental origins of health and disease that the baby’s first environment in its mother’s body has implications for health across the lifespan,” Seng said. “Higher exposure to cortisol may signal the fetus to adapt in ways that help survival, but don’t help health and longevity. This finding is very useful because it helps us know which women are most likely to exhibit the highest level of stress and stress hormones during pregnancy and postpartum.”

    Cortisol is sometimes called the stress hormone because it’s released in stressful situations as part of the flight-or-fight response. Cortisol levels that stay high are linked to serious health problems such as heart disease and high blood pressure, and can fuel weight gain, depression and anxiety plus a host of other problems. The effect of elevated cortisol on a developing fetus isn’t well understood, but high cortisol and stress also contribute to preterm birth.

    In the study, 395 women expecting their first child were divided into four groups: those without trauma, those with a trauma but no PTSD, those with classic PTSD and those with dissociative PTSD.

    Researchers measured salivary cortisol at different times during the day. Then 111 of those women gave saliva specimens until postpartum. The difference in cortisol was greatest in early pregnancy, when levels were eight times higher in the afternoon and 10 times higher at bedtime for the dissociative group than for other women.

    About 8 percent of pregnant women in the study had PTSD, a disorder that results when symptoms of anxiety and fear persist well after exposure to stressful events. About 14 percent of that group had the more complex dissociative PTSD, which was associated with higher cortisol.

    “It’s been a mystery in our field why cortisol is sometimes high with PTSD and sometimes not,” Seng said. “This finding that in pregnancy it’s only the dissociative subgroup that has high cortisol gives us more to go on for future research.”

    Seng was surprised at how high the cortisol was in the dissociative group. She also said researchers expected women with classic PTSD to experience elevated cortisol as well, and the fact that they didn’t is good news.

    “We can do something for the 1-to-2 out of 100 pregnant women who have this dissociative PTSD,” Seng said. “We can work with them to make pregnancy, maternity care, labor, breastfeeding and early parenting less likely to trigger stress reactions. And we can connect them to mental health services when they are ready to treat their PTSD.”

    Seng and collaborator Mickey Sperlich have developed a PTSD-specific education program for pregnant woman with a childhood trauma called the Survivor Moms’ Companion, which has been piloted in Michigan and is currently being piloted in England.


  3. Study suggests preemies’ dads more stressed than moms after NICU

    December 13, 2017 by Ashley

    From the Northwestern University press release:

    For the first time, scientists have measured the stress levels of fathers of premature babies during the tense transition between the Neonatal Intensive Care Unit (NICU) and home and discovered fathers are more stressed than moms, according to a new Northwestern Medicine study.

    Fathers and mothers of these very low birth weight babies had high levels of the stress hormone cortisol in their saliva prior to being discharged. But the fathers experienced an increase in their stress levels as measured several times over the next 14 days at home while the mothers’ stress levels stayed constant.

    “Dad goes from a situation where the baby and mom are cared for by experts in the hospital to having to simultaneously care for his baby, partner and work. He is supposed to be the ‘rock’ for his partner but the stress can really set in,” said lead author Dr. Craig Garfield, associate professor of pediatrics and of medical social sciences at Northwestern University Feinberg School of Medicine.

    The study was published Dec. 1 in the Journal of Perinatal and Neonatal Nursing.

    Garfield and his team measured the parents’ stress levels in two ways: salivary tests that measure cortisol levels and paper surveys. They tested the participants the day before they were discharged from the hospital, then one day, five days and 14 days after coming home.

    “One day of being stressed at home is not a big deal,” said Garfield, who also is an attending pediatrician at Ann & Robert H. Lurie Children’s Hospital of Chicago. “But if their levels are still high after two weeks, that’s more concerning.”

    During the 14 days after arriving home, the fathers’ cortisol levels steadily increased while the mothers’ stress levels returned to “pretty much back to where they started,” Garfield said.

    Interestingly, the fathers’ stress levels based on salivary test results were higher than they reported feeling in the survey. This could indicate that the fathers weren’t in touch with how stressed they really were, Garfield said.

    To help relieve fathers’ stress and ease the transition, Garfield recommends parents place more emphasis on the dad becoming comfortable and gaining confidence with the baby while still in the NICU. Moms need to remember that dads need time to relax, too, Garfield said.

    “Dads should be telling the mom to go take a walk, take a shower, see a friend,” Garfield said. “But moms can also say, ‘Why don’t you go to the gym, see your friends, meet someone after work?’ as ways to reduce some of the stress.”

    “Babies thrive when parents thrive, and if parents are stressed out, that can impact their parenting of the child, the relationship between the mom and dad and can alter infant attachment,” he said. “This all is just much more pronounced with medically vulnerable babies leaving the NICU and going home with mom and dad.”

    While the study didn’t examine stress levels in parents of full-term babies, Garfield said those parents still report feeling stress when returning home.

    “While finally bringing a baby home is really wonderful, it can also be stressful because of sleep deprivation, the lack of control and having to respond constantly to the baby’s needs,” Garfield said.

    The study was funded by the Agency for Health Research and Quality grant number #R21 HS20316 .


  4. Study suggests hair cortisol levels predict which mothers are more likely to suffer postpartum depression

    November 19, 2017 by Ashley

    From the University of Granada press release:

    Researchers from the University of Granada (UGR), who belong to the Brain, Mind and Behavior Research Center (CIMCYC, from its abbreviation in Spanish) and the Faculty of Psychology, have proven that cortisol levels (a steroid hormone secreted as a response to stress) present in the hair of pregnant women during the first or third trimesters of pregnancy may indicate which of them are more likely to suffer postpartum depression.

    Their work, published in the PLoS ONE journal, showed that hair cortisol levels in women who developed postpartum depression were higher throughout pregnancy than those seen in women who hadn’t developed it, being that difference statistically more significant during the first and third trimesters.

    The UGR researchers carried out their study doing a follow-up on 44 pregnant women throughout the whole gestation period and after giving birth. Each trimester the mothers underwent a series of tests that evaluated their stress and psychopathological symptoms while simultaneously taking hair samples from which the researchers extracted the cortisol corresponding to the last three months.

    The following days after labor the researchers evaluated the mothers’ emotional state in order to assess who among them had developed postpartum depression.

    Quarterly psychopathological symptoms

    Additionally, the results of the study showed that the participants which developed postpartum depression showed higher levels of somatization during the first trimester. During the second trimester they showed higher levels of somatization, obsession-compulsion, depression and anxiety, and during the third trimester they showed higher levels of somatization and pregnancy-specific stress. Therefore, all those symptoms along with higher levels of cortisol would be indicators of a future postpartum depression.

    As María Isabel Peralta Ramírez, lead researcher of the project says, the consequences of those results are very important in the prevention of postpartum depression, “since they show that there are various altered psychological and hormonal variables throughout the whole gestation period in comparison to those women who will not suffer postpartum depression. Detecting those differences is the key to anticipate the psychological state of the mother as well as the consequences for the baby that said state could mean.”

    This study belongs to the GESTASTRESS research project, in the research excellence framework of the Spanish Ministry of Economy and Competitiveness. Its primary goal has been to assess the effects of psychological stress on the mother throughout the whole gestation period as well as on birth variables, and on the baby’s stress and neurodevelopment.


  5. Higher estrogen levels linked to increased alcohol sensitivity in brain’s ‘reward center’

    November 14, 2017 by Ashley

    From the University of Illinois at Chicago press release:

    The reward center of the brain is much more attuned to the pleasurable effects of alcohol when estrogen levels are elevated, an effect that may underlie the development of addiction in women, according to a study on mice at the University of Illinois at Chicago.

    Led by Amy Lasek, assistant professor of psychiatry in the UIC College of Medicine, researchers found that neurons in a region of the brain called the ventral tegmental area, or VTA (also known as the “reward center”), fired most rapidly in response to alcohol when their estrogen levels were high. This response, according to their findings published online in the journal PLOS ONE, is mediated through receptors on dopamine-emitting neurons in the VTA.

    “When estrogen levels are higher, alcohol is much more rewarding,” said Lasek, who is the corresponding author on the paper and a researcher in the UIC Center for Alcohol Research in Epigenetics. “Women may be more vulnerable to the effects of alcohol or more likely to overindulge during certain stages of their cycle when estrogen levels are higher, or may be more likely to seek out alcohol during those stages.”

    Studies indicate that gender differences in psychiatric disorders, including addiction, are influenced by estrogen, one of the primary female sex hormones. Women are more likely to exhibit greater escalation of abuse of alcohol and other drugs, and are more prone to relapse in response to stress and anxiety.

    The VTA helps evaluate whether something is valuable or good. When neurons in this area of the brain are stimulated, they release dopamine — a powerful neurotransmitter responsible for feelings of wellness — and, in large doses, euphoria. When something good is encountered — for example, chocolate — the neurons in the VTA fire more rapidly, enforcing reward circuitry that encodes the idea that chocolate is enjoyable and something to be sought out. Over time, the VTA neurons fire more quickly at the sight, or even thought of, chocolate, explained Lasek. In addiction, VTA neurons are tuned into drugs of abuse, and fire more quickly in relation to consuming or even thinking about drugs, driving the person to seek them out — often at the expense of their own health, family, friends and jobs.

    Many animal studies have shown that alcohol increases the firing of dopamine-sensitive neurons in the VTA, but little is known about exactly why this occurs.

    Lasek and her colleagues examined the relationship between estrogen, alcohol and the VTA in female mice. They used naturally cycling mice that were allowed to go through their normal estrous cycles, akin to the menstrual cycle in women.

    Mice were evaluated to determine when they entered diestrus — the phase in the estrous cycle when estrogen levels are close to their peak.

    “In mice in diestrus, estrogen levels increase to about 10 times higher than they are in estrus, the phase in which ovulation occurs and estrogen levels drop,” Lasek said.

    VTAs were taken from mice in both estrus and diestrus and kept alive in special chambers. Electrodes recorded the activity of individual dopamine-sensitive neurons in the VTA. Next, the researchers added alcohol to the chamber. Activity increased twice as much in neurons from mice in diestrus compared to the response of neurons from mice in estrus.

    Lasek and her colleagues then blocked estrogen receptors on dopamine-sensitive neurons in VTA in mice in estrus and diestrus. With the blocker present, the response to alcohol in neurons from mice in diestrus was significantly lower compared with neurons where estrogen receptors remained functional. The estrogen receptor blocker reduced the alcohol response to levels seen in mice in estrus. The responses to alcohol in neurons from mice in estrus were unaffected by the estrogen receptor blocker.

    “The increased reward response to alcohol we see when estrogen levels are high is mediated through receptors for estrogen in the VTA,” said Mark Brodie, professor of physiology and biophysics in the UIC College of Medicine and a co-author on the paper.

    Lasek believes that the increased sensitivity to alcohol in the VTA when estrogen levels peak may play a significant role in the development of addiction in women.

    “We already know that binge drinking can lead to lasting changes in the brain, and in women, those changes may be faster and more significant due to the interaction we see between alcohol, the VTA and estrogen,” Lasek said. “Binge drinking can increase the risk of developing alcoholism, so women need to be careful about how much alcohol they drink. They should be aware that they may sometimes inadvertently over-consume alcohol because the area of the brain involved in alcohol reward is responding very strongly.”


  6. Study suggests there may be potential cognitive benefits to hormone replacement therapy

    November 4, 2017 by Ashley

    From the University of Southern California press release:

    A type of hormone replacement therapy may protect memory for some women, according to a new USC-led study.

    The findings by USC researchers are the latest to indicate that hormone replacement therapy may have some benefits, deepening scientific discussions about the pros and cons of the menopausal treatment.

    “Our study suggests that estrogen treatment after menopause protects the memory that is needed for short-term cognitive tasks from the effects of stress,” said Alexandra Ycaza Herrera, the study’s lead author and a researcher at the USC Leonard Davis School of Gerontology.

    Earlier studies have pointed to potential health risks of the treatment. A combination therapy that uses both estrogen and progesterone has been linked to a higher risk of breast cancer, heart disease, stroke and blood clots.

    The study was published on Nov. 2 in the Journal of Clinical Endocrinology and Metabolism.

    The researchers found that women taking estrogen-only therapy had lower levels of the stress hormone cortisol and performed better on tests of “working memory” following exposure to stress compared to women taking a placebo.

    Working memory allows the brain to keep information immediately available for processing, such as when a shopper uses a mental grocery list to pick up items or when a student keeps specific numbers in mind as a teacher reads a word problem aloud in math class. Studies have documented that stress can impair working memory.

    To measure the effect of estrogen therapy on working memory under stress, Ycaza Herrera recruited 42 women with an average age of 66 from the USC Early versus Late Intervention Trial with Estradiol led by Howard Hodis, a professor at the Keck School of Medicine of USC and a coauthor of the new study.

    Half of the postmenopausal women had been on estradiol, a type of estrogen therapy, for approximately five years, while the others had received a placebo.

    Each participant visited USC twice. To induce a stress response during one visit, researchers asked participants to submerge their hand in ice water for about 3 minutes. For the control condition conducted during the other visit, the participants submerged their hand in warm water.

    Before and after each visit, the researchers collected saliva to measure the women’s levels of cortisol, estrogen, and progesterone. The researchers also ran a test of working memory called a “sentence span task,” in which the women were each given a series and then asked whether each sentence made sense. They also were asked to recall the last word of each one.

    All women performed equally well on the sentence span task after the warm water condition. But after the ice bath, women taking the placebo experienced a spike in cortisol levels. They also demonstrated a decrease in working memory function.

    By contrast, women receiving estrogen therapy had a smaller increase in cortisol and showed no decrease in working memory function.

    “Hormone replacement therapy may not be right for every woman, but women need to be able to have the conversation with their doctors,” Ycaza Herrera said.


  7. Study links testosterone to stock market instability

    October 14, 2017 by Ashley

    From the Institute for Operations Research and the Management Sciences press release:

    In the U.S. today, the majority of professional stock market traders are young males and new evidence suggests biology strongly influences their trading behavior. According to a new study in the INFORMS journal Management Science, this could be a significant contributor to fluctuations in the market, as high testosterone levels can cause these traders to overestimate future stock values and change their trading behavior, leading to dangerous prices bubbles and subsequent crashes.

    The study, “The Bull of Wall Street: Experimental Analysis of Testosterone and Asset Trading,” was conducted by Amos Nadler of the Ivey Business School at Western University, Peiran Jiao of the University of Oxford, Paul Zak and Veronika Alexander of the Center for Neuroeconomics Studies at Claremont Graduate University, and Cameron Johnson at the Behavioral Health Institute at Loma Linda.

    The double blind study involved 140 young males, each of whom received a topical gel containing either testosterone or a placebo, prior to participating in an experimental asset market in which they were able to post bid and ask prices, as well as buy and sell financial assets to earn real money.

    The authors found that among groups that received testosterone relative to those who received a placebo, larger price bubbles formed, mispricing lasted longer, market dynamics changed to reflect increasing bidding and selling volume, and their perception of a stock’s value changed despite its being displayed throughout the study. While the traders who received the placebo displayed “buy low to sell high” behavior, those who had received testosterone adhered to “buy high to sell higher.”

    “This research suggests the need to consider hormonal influences on decision-making in professional settings, because biological factors can exacerbate capital risk,” said Nadler. “Perhaps the simplest recommendation is to implement ‘cool down’ periods to interrupt exceptionally positive feedback cycles and return the focus to assets’ fundamental valuations to reduce the possibility of biased decision-making.”

    “Based on our findings, professional traders, investment advisories, and hedge funds should limit the risk taken by young male traders,” continued Nadler. “This is the first study to have shown that testosterone changes the way the brain calculates value and returns in the stock market and therefore — testosterone’s neurologic influence will cause traders to make suboptimal decisions unless systems prevent them from occurring.”


  8. Study examines effect of oxytocin on sociability

    October 8, 2017 by Ashley

    From the Stanford University Medical Center press release:

    Why is it so much fun to hang out with our friends? Why are some people so sociable while others are loners or seemingly outright allergic to interactions with others?

    A new study by researchers at the Stanford University School of Medicine begins to provide an answer, pinpointing places and processes in the brain that promote socialization by providing pleasurable sensations when it occurs. The findings point to potential ways of helping people, such as those with autism or schizophrenia, who can be painfully averse to socializing.

    The study, which will be published Sept. 29 in Science, details the role of a substance called oxytocin in fostering and maintaining sociability. The senior author is Robert Malenka, MD, PhD, professor and associate chair of psychiatry and behavioral science. The lead author is former postdoctoral scholar Lin Hung, PhD.

    “Our study reveals new insights about the brain circuitry behind social reward, the positive experience you often get when you run into an old friend or meet somebody you like,” said Malenka, who has focused much of his research on an assembly of interacting nerve tracts in the brain collectively known as the reward circuitry.

    “The reward circuitry is crucial to our survival because it rewards us for doing things that have, during our evolutionary history, tended to enhance our survival, our reproduction and the survival of our resulting offspring,” said Malenka, who holds the Nancy Friend Pritzker Professorship in Psychiatry and the Behavioral Sciences. “It tells us what’s good by making us feel good. When you’re hungry, food tastes great. When you’re thirsty, water is refreshing. Sex is great pretty much most of the time. Hanging out with your friends confers a survival advantage, too, by decreasing your chances of getting eaten by predators, increasing your chances of finding a mate and maybe helping you learn where food and water are.”

    Reward system conserved over evolution

    Because the reward system is so critical, it’s been carefully conserved over evolution and in many respects operates just the same way in mice as it does in humans, making mice good experimental models for studying it.

    Far and away the most important component of the brain’s reward circuitry, Malenka said, is a nerve tract that runs from a structure deep in the brain called the ventral tegmental area to a midbrain structure called the nucleus accumbens. The ventral tegmental area houses a cluster of nerve cells, or neurons, whose projections to the nucleus accumbens secrete a substance called dopamine, altering neuronal activity in this region. Dopamine release in the nucleus accumbens can produce a wave of pleasure, telling the brain that the event going on is helpful for survival. Dopamine release in this region, and subsequent changes in activity there and in downstream neurons, also prime the brain to remember the events and the behaviors leading up to the chemical’s release.

    This tract, so famous for reinforcing survival-enhancing behaviors such as eating, drinking and mating, has been infamously implicated in our vulnerability to drug addiction — a survival-threatening outcome resulting from drugs’ ability to inappropriately stimulate dopamine secretion in the tract. But understanding exactly how and under what natural conditions the firing of its dopamine-secreting nerves gets tripped off is a work in progress.

    Earlier research has specifically implicated dopamine release in the nucleus accumbens in social behavior. “So, we knew reward circuitry plays a role in social interactions,” Malenka said. “What we still didn’t know — but now we do — was: How does this increased dopamine release during social interaction come about?”

    ‘Love hormone’ pulls the strings

    It turns out that another chemical — oxytocin — is pulling the strings.

    Oxytocin is sometimes called the “love hormone” because it’s thought to be involved in falling in love, mother-child bonding and female sexual arousal, as well as lifetime pair-bonding of sexual mates among some species. The chief source of oxytocin in the brain is the paraventricular nucleus, which resides in a deep-brain structure called the hypothalamus that serves as a manifold master regulator of body temperature, hunger, thirst, sleep, emotional reactions and more.

    Research over the last 20 to 40 years has suggested that oxytocin plays a role in promoting not just sexual or nurturing behavior, but also sociability. A 2013 study co-authored by Malenka showed that oxytocin was essential to reinforcing friendly, social behavior in mice. But how that occurred was unclear, as the paraventricular nucleus sends oxytocin-squirting nerve tracts to many areas throughout the brain.

    So Malenka and his colleagues designed experiments to nail down oxytocin’s role in social behavior. They confirmed that a tract running from the paraventricular nucleus to the ventral tegmental area carried oxytocin. They showed, for the first time, that activity in this tract’s oxytocin-secreting neurons jumped during mice’s social interactions and that this neuronal activity was required for their normal social behavior. Disrupting this activity inhibited sociability but didn’t impair the mice’s movement or their appetite for pleasurable drugs, such as cocaine.

    The researchers demonstrated that oxytocin secreted in the ventral tegmental area by neurons originating in the paraventricular nucleus fosters sociability by binding to receptors on the dopamine-secreting neurons that compose the tract running from the ventral tegmental area to the nucleus accumbens, enhancing the firing of the reward-circuit tract.

    The findings should help translational researchers develop medications for individuals with neurological disorders, such as autism, depression and schizophrenia, whose conditions compromise their ability to experience pleasure from connecting with other people, Malenka said.

    But he also voiced a desire for more widespread applications of the research. “With so much hatred and anger in the world,” he said, “what could possibly be more important than understanding the mechanisms in the brain that make us want to be friendly with other people?”


  9. Study links dogs’ social skills to oxytocin sensitivity

    October 5, 2017 by Ashley

    From the Linköping University press release:

    The tendency of dogs to seek contact with their owners is associated with genetic variations in sensitivity for the hormone oxytocin, according to a new study from Linköping University, Sweden. The results have been published in the scientific journal Hormones and Behavior and contribute to our knowledge of how dogs have changed during their development from wolf to household pet.

    During their domestication from their wild ancestor the wolf to the pets we have today, dogs have developed a unique ability to work together with humans. One aspect of this is their willingness to “ask for help” when faced with a problem that seems to be too difficult. There are, however, large differences between breeds, and between dogs of the same breed. A research group in Linköping, led by Professor Per Jensen, has discovered a possible explanation of why dogs differ in their willingness to collaborate with humans.

    The researchers suspected that the hormone oxytocin was involved. It is well-known that oxytocin plays a role in social relationships between individuals, in both humans and animals. The effect of oxytocin depends on the function of the structure that it binds to, the receptor, in the cell. Previous studies have suggested, among other things, that differences in dogs’ ability to communicate are associated with variations in the genetic material located close to the gene that codes for the oxytocin receptor. The researchers in the present study examined 60 golden retrievers as they attempted to solve an insoluble problem.

    “The first step was to teach the dogs to open a lid, and in this way get hold of a treat. After this, they were given the same task with the lid firmly fixed in place, and thus impossible to open. We timed the dogs to see how long they attempted on their own, before turning to their owner and asking for help,” says Mia Persson, PhD student at the Department of Physics, Chemistry and Biology, and principal author of the article.

    Before the behavioural test, the researchers increased the levels of oxytocin in the dogs’ blood by spraying the hormone into their nose. As a control, the dogs carried out the same test after having received a spray of neutral salt water in the same way. The researchers also collected DNA using a cotton swab inside the dogs’ cheek, and determined which variant of the gene for the oxytocin receptor that each dog had.

    The results showed that dogs with a particular genetic variant of the receptor reacted more strongly to the oxytocin spray than other dogs. The tendency to approach their owner for help increased when they received oxytocin in their nose, compared with when they received the neutral salt water solution. The researchers suggest that these results help us understand how dogs have changed during the process of domestication. They analysed DNA also from 21 wolves, and found the same genetic variation among them. This suggests that the genetic variation was already present when domestication of the dogs started, 15,000 years ago.

    “The results lead us to surmise that people selected for domestication wolves with a particularly well-developed ability to collaborate, and then bred subsequent generations from these,” says Mia Persson.

    The genetic variations that the researchers have studied do not affect the oxytocin receptor itself: they are markers used for practical reasons. Further research is necessary to determine in more detail which differences in the genetic material lie behind the effects.

    Per Jensen points out that the study shows how social behaviour is to a large extent controlled by the same genetic factors in different species.

    “Oxytocin is extremely important in the social interactions between people. And we also have similar variations in genes in this hormone system. This is why studying dog behaviour can help us understand ourselves, and may in the long term contribute to knowledge about various disturbances in social functioning,” he says.


  10. Study suggests oxytocin can intensify both positive and negative experiences

    September 30, 2017 by Ashley

    From the University of California – Davis press release:

    Before you shop for the “cuddle” hormone oxytocin to relieve stress and enhance your social life, read this: a new study from the University of California, Davis, suggests that sometimes, blocking the action of oxytocin in the brain may be a better option. The results are published online in the journal Biological Psychiatry.

    Sometimes popularly called the “love hormone,” oxytocin is a hormone released in the brain that plays a major role in social relationships. The new work by behavioral neuroscientists Natalia Duque-Wilckens and Brian Trainor shows that after negative social interactions, oxytocin promotes avoidance of unfamiliar social situations.

    Trainor and Duque-Wilckens worked with female California mice. When stressed, these mice can show a form of social anxiety, staying away from unfamiliar mice instead of approaching. The new study shows that a single dose of a drug that blocks the activity of oxytocin restored normal social behavior in stressed females.

    The result is exciting because “for antidepressants like Prozac to have this same effect, it takes a month of daily treatment,” said Trainor, a professor in the UC Davis Department of Psychology, College of Letters and Science.

    This outcome was expected based on a previous study from the lab, which showed that social stress increased the activity of oxytocin-producing cells in the brain and that females given intranasal oxytocin avoided new social contexts.

    Amplifying Positive and Negative Effects

    Postdoctoral researcher Duque-Wilckens said that these findings support the theory that oxytocin amplifies the effects of social experiences. That is, rather than promoting positive social interactions, oxytocin intensifies the experience of both positive and negative social interactions.

    In a positive context, such as with family or friends, oxytocin could promote social approach behavior (hence the “cuddling” hormone). However, in a negative context, like bullying, oxytocin could promote social avoidance. One question left unanswered by this theory is how the same hormone could have such different effects on behavior. The new study led by Duque-Wilckens provides an explanation.

    The team found that two brain regions responded to oxytocin more strongly in females than males. These regions were the bed nucleus of the stria terminalis (BNST), a brain region known to control anxiety, and the nucleus accumbens, a brain region important for reward and motivation. Duque-Wilckens found that injecting an oxytocin blocker into the BNST, but not the nucleus accumbens, reversed the effects of stress on social behavior in females. Work by other researchers has shown that oxytocin acting in the nucleus accumbens promotes rewarding aspects of social interactions.

    Together, these findings suggest that oxytocin can generate social anxiety or reward by acting in different parts of the brain. At times when oxytocin is acting in the BNST, drugs that inhibit oxytocin could reduce social anxiety.

    Trainor said a consistent theme in oxytocin research is that experience and the surrounding environment have important effects on how oxytocin affects behavior.

    “Stressful social experiences appear to change which parts of the brain use oxytocin,” he said. “Understanding how this works in a mouse gives us new ideas on how we could use drugs targeting oxytocin to reduce social anxiety.”