Every day, the seven National Primate Research Centers (NPRCs) conduct and enable collaborative research studies to improve human and animal health. For more than five years now, we’ve been sharing our latest news and scientific advancements with you via NPRC.org and @NPRCnews (X), and there’s more coming your way. 

To ensure the NPRCs provide the topics of most interest to our readers and followers, we looked back at your favorite stories to help us move forward. Your top interests span behavior and psychology, infectious disease and neuroscience and brain disorders research. We will continue to share news that represents what you have most enjoyed, and we will also bring you information that reflects the breadth and depth of research across the NPRC network.   

We appreciate our readers and followers, and encourage you to take another look at your favorite blogs about NPRC research, to share the information with your family, friends and colleagues, and to continue connecting with us via NPRC.org, @NPRCnews and, now, on the new NPRC LinkedIn account. Via these resources, you’ll always be able to access the latest news on NPRC research that is helping people across generations and around the world live longer, healthier lives.   

Behavior and Psychology 

1. The Effects of Wildfire Smoke Exposure in Early Pregnancy 

A study by California NPRC and UC Davis researchers investigated the effects of wildfire smoke exposure on infant monkeys during early pregnancy. The study found that exposure led to increased inflammation, reduced stress response, memory deficits and a more passive temperament in the monkeys. The findings suggest environmental changes during pregnancy can have lasting effects on offspring.  

Infectious Disease 

2. A Deadly Relationship: Stopping the Progression of Tuberculosis in HIV Patients   

Researchers at the Southwest National Primate Research Center have discovered chronic immune activation in the lungs plays a crucial role in the progression of tuberculosis (TB) and HIV co-infection. This dysfunction hampers the body’s ability to fight off infections. The study suggests the need to develop treatments targeting chronic immune activation alongside antiretroviral therapy (ART). TB and HIV are global pandemics that reinforce each other, affecting a significant portion of the world’s population. The findings offer hope for improved treatment strategies in the next decade. 

3. New Possible Correlation Between Lyme Disease and Lewy Body Dementia  

At Tulane National Primate Research Center, researchers discovered intact spirochetes of Borrelia burgdorferi, the bacterium that causes Lyme disease, in the central nervous system of a 69-year-old woman who received multiple rounds of antibiotic treatment. The presence of this bacterium coupled with her persistent neurological decline raises the possibility of a correlation between Lyme disease and Lewy body dementia. This finding highlights the bacterium’s persistence despite targeted therapy and emphasizes the need for further research to comprehend its role in severe neurological conditions. 

4. Are DNA Vaccinations a Perennial Answer to the Flu?  

Researchers at the Washington National Primate Research Center are developing a universal flu vaccine that could protect against all strains of the influenza virus. Using a DNA vaccine administered through the skin, the team has achieved promising results in macaques, providing 100% protection against a previous flu virus. This approach could eliminate the need for annual flu shots and be quickly deployed during pandemics. The researchers believe this technology could also be effective against other viruses and outbreaks. 

Neuroscience & Brain Disorders 

5. Past Social Experiences May Affect Brain’s Response to Oxytocin

A study at the Emory (formerly Yerkes) National Primate Research Center and Emory University showed the response of neurons to oxytocin, a chemical involved in social bonding, can vary based on an individual’s past experiences. Using female prairie voles, the researchers examined the nucleus accumbens, a brain region related to pair bonding. They found that oxytocin reduced neuron firing before bonding and increased it afterward, when triggered. The study also revealed a connection between oxytocin signals and endocannabinoids, affecting defensive interactions. These findings provide insights into how prior experiences influence oxytocin’s impact on brain circuits. 

6. NPRC Study May Have Found Link That Causes Anxiety and Depression  

Researchers at the Wisconsin National Primate Research Center and the University of Wisconsin-Madison have discovered brain pathways in juvenile monkeys that could contribute to anxiety and depression later in life. By studying the connections between specific brain regions, they found a correlation between synchronization and anxious temperament. These findings may lead to better treatment approaches and help identify gene alterations associated with anxiety. 

7. The Drinking Gene: Could Alcoholism Be Inherited?  

Research conducted at Oregon National Primate Research Center has identified a gene, GPR39, as a potential target for developing medication to prevent and treat alcoholism. By modifying protein levels encoded by this gene in mice, the researchers observed a significant reduction in alcohol consumption. They also found a link between alcohol and the activity of this gene. The study draws attention to the importance of cross-species approaches to identify drugs for treating alcohol use disorder. Further investigations are under way to determine if the same mechanism applies to humans. These findings offer potential insights for developing drugs to address chronic alcoholism and mood disorders. 

Many previous studies explain how exposure to certain environmental substances during pregnancy may affect your baby’s health. Toxic substances increase the risk for congenital disabilities, low birth weight, prematurity, and miscarriage.

Studying the long-term effects of various environmental changes during pregnancy has occurred for decades¾from exposure to metals, cigarette smoke, stress, radiation, and more. But, recently, a new study at the California National Primate Research Center at the University of California, Davis, was published exploring the effects of wildfire smoke exposure during early pregnancy on a group of infant monkeys.

It’s typically challenging to study exposure to environmental variations during early pregnancy in women because they often aren’t aware of their pregnancies until weeks after conception. But a fire beginning on November 8, 2018, in Davis, California, provided a natural experiment in wildfire smoke exposure for a group of rhesus macaques housed close by in outdoor corrals at the California National Primate Research Center during mating season. Just under 90 monkeys were born six months later.

After months, studies proved the baby monkeys exposed to smoke had increased inflammation, reduced cortisol response to stress, memory deficits, and a more passive temperament than other animals.

Because of this study’s findings, Bill Lasley, professor emeritus of population health and reproduction at the UC Davis School of Veterinary Medicine and Center for Health and Environment, plans to study women who became pregnant through IVF. This allows him and his team to look at more prolonged-term effects of wildfire exposure with the added benefit of knowing the exact time of conception.

When you think of Rhesus macaques, one typically doesn’t feel that it has an innate ability to sense the internal state of its own body, like observing the quickening of its heartbeat. Until recently, scientists would have agreed, too. But a new study conducted by the California National Primate Research Center at the University of California, Davis, and Royal Holloway, University of London, is changing the way researchers think.

During this study, a team of researchers monitored four rhesus monkeys for their reaction to a stimulus. As it turns out, all four monkeys spent more time watching the out-of-rhythm stimuli. What does this mean? They have a human-like ability to perceive their heartbeats and have an interoceptive sense.

Interception is critically important to helping your brain identify things happening in your body, like when your breathing quickens or heart races. The brain uses information about how your body is feeling to collect feedback on your current emotions. 

Many people with conditions like ADHD, autism, trauma disorders, depression, anxiety, and Alzheimer’s disease have been found to have interception difficulties. 

Eliza Bliss-Moreau, associate professor of psychology at UC Davis and core scientist at the CNPRC states, “Our model will be used in future translational studies of neurodegenerative diseases, including Alzheimer’s. If we can measure interoception, we can track it as a behavioral biomarker of disease progression.

The published paper concludes that the next step is to study how interoception may be involved in other psychiatric and neuropsychiatric conditions.

Adolescents may face many challenges throughout their teenage years, from depression and poor body image to loneliness and even substance abuse. To help address and limit these concerns, researchers are continually looking for connections between the human brain, environment and mental health.

The impact of COVID-19 on adolescent mental health is especially important to address following the social isolation intended to limit the spread of the virus. Yerkes National Primate Research Center neuroscientist Shannon Gourley’s research on the effect of isolation on adolescent mice will be a resource to researchers studying how the COVID-19 pandemic has affected children.

Gourley’s research provides insights into adolescent brain mechanisms. She and her research team discovered mice that have a history of social isolation have higher dendritic spine densities in regions of the brain relevant to decision-making, such as the prefrontal cortex. Social isolation interferes with the pruning of dendritic spines, the structures that underlie connections between neurons.

While we typically think more of something is better, this is not the case for dendritic spines. Instead, such elevated levels related to social adversity experienced during sensitive adolescent periods lead to long-term consequences, despite a typical social environment later in life.

Gourley says, “our findings suggest adolescence is a critical period during which social experience optimizes one’s ability to seek and attain goals later in life.”

Interrupting social experiences may translate into poor choices about homework, food and even hygiene, and that makes Gourley’s research critical now and in the future to help her team and other researchers counter additional, long-term impacts of COVID-19.

The road to addiction recovery might become a little less rocky, thanks to a recent study by researchers at the Yerkes National Primate Research Center. Researchers suggest the drug fasudil, approved in Japan for cerebral vasospasm and stroke, could be an effective tool for treating drug abuse and preventing relapse.

Most of our everyday actions come from habits, not from deliberate decision-making. This can be detrimental in the case of drug abuse and drug-seeking behavior, says lead author Shannon Gourley, assistant professor of pediatrics, psychiatry and behavioral sciences at Emory University School of Medicine and Yerkes National Primate Research Center.

“Some habits are adaptive – for example, turning off a light when you exit a room – but others can be maladaptive, for example in the case of habitual drug use. We wanted to try to figure out a way to help ‘break’ habits, particularly those related to the highly addictive drug cocaine,” says Gourley.

She and former graduate students Andrew Swanson and Lauren Depoy first tested fasudil in situations where they had trained mice to poke their noses in two chambers, based on rewards of both food and cocaine. Then, the researchers changed the rules of the game – mice could now only get a reward from one chamber, instead of both. Fasudil helped the mice adjust and display “goal-directed” behavior, rather than their previous habit-based behavior.

Next, the researchers trained the mice to supply themselves a sweet cocaine solution. After the mice formed habit-based behavior, researchers changed the nature of that experience: the cocaine was paired with lithium chloride, making the mice feel sick. Fasudil treatment nudged the mice to give themselves less cocaine afterward, rather than continuing to respond habitually. Fasudil didn’t make cocaine itself less pleasurable, but was specifically modifying the habit process.

Unlearning habits involves remodeling connections made by cells in the brain. Fasudil seems to promote the pruning of dendritic spines, structures that help neurons communicate, by inhibiting Rho kinase, which helps stabilize cells’ internal skeletons. The drug thereby loosens the cell structures and appears to reduce the density of dendritic spines in the region of the brain important for learning new behaviors. Importantly, tests show fasudil must be directly paired with new learning to have that effect.

While overactive synaptic pruning has been proposed to play roles in Alzheimer’s disease and schizophrenia, when used appropriately, fasudil and similar compounds are promising candidates for drug addiction therapy.

Reviewed August 2019

An estimated 15.1 million adults in the United States have Alcohol Use Disorder (AUD), a chronic brain disease characterized by compulsive alcohol use. This includes approximately 6.2 percent of all American adults, a staggering percentage of drinkers nationwide.

“The amount of alcohol consumed in the US is not only substantial, but unequally divided in terms of who drinks how much,” said Dr. Kathleen Grant, Chief and Senior Scientist of Behavioral Neuroscience at the Oregon National Primate Research Center (ONPRC). “A small proportion drink the vast majority of alcohol sold.”

But why can some people safely enjoy a single nightcap, while others are at risk for developing alcoholism or a serious alcohol problem?

Dr. Grant hopes to answer that very question by studying a population of rhesus monkeys. Through her research, she is unraveling why some people are at a greater risk for heavy drinking habits.

Dr. Grant studies monkeys who have been exposed to alcohol over the course of three months. Like humans, some choose to drink water, some choose to drink alcohol, and some choose to drink a combination of the two. Understanding why certain monkeys choose to drink alcohol heavily provides clues as to why some humans are at a higher risk for developing a drinking problem.

Dr. Grant has found that males – both monkeys and humans – are more likely to become problem alcohol drinkers than females. In addition, monkeys that are exposed to stressful situations or stimuli choose to drink alcohol more than those that are not.

However, there are several risk factors that affect humans, but are not seen in monkeys. For example, in humans, family history of alcoholism can affect one’s inherited genes and environment and ultimately lead to an increased risk of heavy drinking. In addition, drinking alcohol between the ages of 13-15 increases the lifetime chances of being diagnosed with alcohol dependence.

Ultimately, Dr. Grant hopes her research will help identify those at risk for developing alcoholism before they’ve developed an alcohol addiction. By determining certain biomarkers in the brain and blood, she is hopeful that, eventually, we can caution people that they’re heading toward addiction before it begins.

“Prevention would be so much better for everyone because alcoholism affects more than just the individual,” Dr. Grant said.

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Photo credit: Kathy West for the California National Primate Research Center

Kids can inherit their parents’ eye color, hair type, and even bone structure. But can genetics also explain a child’s anxiety levels? Researchers from the University of Wisconsin-Madison (UW) investigated whether there is a generational link for anxiety.

The study from UW’s Department of Psychiatry and the HealthEmotions Research Institute examined a large, multi-generational family of nearly 600 rhesus monkeys. Like humans, monkeys can become anxious when exposed to unfamiliar people, environment, or circumstances. In this study, monkeys were exposed to strangers who did not make eye contact – a situation that a human child may encounter.

During this situation, scientists used medical imaging methods commonly used on humans, including positron emission tomography (PET scans) exams, to identify the regions of the brain affected by anxiety. Once these medical images were taken, researchers compared brain activity within the rhesus family tree. The researchers found increased  activity across three parts of the brain 1) the amygdala, 2) the limbic brain fear center, and 3) the pre-frontal cortex.

“Over-activity of these three regions of the brain is directly linked to the later life risk to develop anxiety and depression,” said Dr. Ned Kalin, Wisconsin National Primate Research Center scientist and chair of psychiatry at the UW School of Medicine and Public Health. “This is a big step in understanding the neural underpinnings of inherited anxiety.”

This research marks a breakthrough in adolescent anxiety-related research, as it helps explain how genetics might affect brain function. Indeed, it was found that about 35% of anxiety tendencies can be explained by family history. Moreover, half of children who show extreme anxiety symptoms develop stress-related psychiatric disorders later in life.

“Now that we know where to look, we can develop a better understanding of the alterations that give rise to anxiety-related brain function,” Dr. Kalin said. “Our genes shape our brains to help make us who we are.”

Reviewed August 2019

According to the Centers for Disease Control and Prevention (CDC), more than 1 in 10 U.S. school-aged kids have received an Attention Deficit Hyperactivity Disorder, or ADHD, diagnosis. That’s 6.4 million children who struggle with inattentiveness, hyperactivity, and – as Dr. Luis Populin from the University of Wisconsin (UW) studies – impulsive behavior.

“If you say to an impulsive child, ‘Do your homework so you will get a good grade at the end of the quarter,’ that has less appeal than ‘Let’s play baseball this afternoon instead of studying chemistry,’” said Dr. Populin, an associate professor of neuroscience at UW-Madison.

To measure impulsive behavior, Dr. Populin studied rhesus monkeys at the Wisconsin National Primate Research Center who showed signs of ADHD, measuring the effects of methylphenidate (or Ritalin, a common ADHD drug) on their working memory and other aspects of executive functioning.

In the study, monkeys who exhibited calmer behavior learned to wait for a larger, delayed reward, while monkeys who tended to fidget and act nervously always chose the immediate, but smaller incentive. This willingness to take a small reward right away, rather than wait for the larger, delayed reward is called “temporal discounting.”

However, when given doses of methylphenidate, both monkeys chose the delayed reward more frequently, improving the condition of temporal discounting – but perhaps impacting other areas of the brain.

Armed with this information, Dr. Populin hopes to devise a mathematical tool that will help a doctor choose the correct dosage to reduce a child’s impulsive behavior – but not hinder executive function skills.

To continue his research, Dr. Populin was awarded the prestigious Hartwell Individual Biomedical Research Award, which provides research funding for three years. With this funding, Dr. Populin and his team are continuing their study of ADHD, examining kid’s temporal discounting (also known as delay discount and time discounting) while playing computer games.

“We will test temporal discounting with a game that kids don’t see as boring, but is still able to evaluate impulsivity so the doctor can make a faster, more accurate dosage calculations,” said Dr. Populin. “Then everybody benefits.”