Posts tagged neuroscience

Quick eye movements, called saccades, that enable us to scan a visual scene appear to act as a metronome for pushing information about that scene into memory.

Scientists at Yerkes National Primate Research Center, Emory University, have observed that in monkeys exploring images with their eyes, the onset of a saccade resets the rhythms of electrical activity (theta oscillations) in the hippocampus, a region of the brain important for memory formation.

Tracking eye movements is already a promising basis for diagnosing brain disorders such as Alzheimer’s disease and schizophrenia. A deeper understanding of how the rhythm of eye movements orchestrate memories could bolster the accuracy and power of eye-tracking diagnoses.

The findings were published this week in Proceedings of the National Academy of Sciences, Early Edition.

Senior author Elizabeth Buffalo was a researcher at the Yerkes National Primate Research Center and an associate professor of neurology at Emory University School of Medicine and is currently associate professor of physiology and biophysics at Universpity of Washington in Seattle. The first author of the paper is postdoctoral fellow Michael Jutras„ who is now an instructor at the University of Washington.

Theta oscillations are cycles of electrical activity in the brain occurring between 3 to 12 times per second. Scientists have previously seen theta oscillations in the hippocampus in rodents, when the rodents were actively exploring, sniffing or feeling something with their whiskers.

"Both animals and humans seem to take in sensory information at this theta rhythm," Buffalo says. "But one striking difference between rodents and primates is the way they gather information about the external world. Rodents are much more reliant on the senses of smell and touch."

She says the actions that are most comparable to rodents’ sniffing and whiskering in primates are saccades. When our eyes scan text or explore a picture, the eyes’ focus tends to jump from point to point several times per second.

Buffalo and Jutras examined electrical signals in the hippocampi of two rhesus monkeys while the monkeys were looking at a variety of pictures and the researchers tracked their eye movements. The researchers observed that after a saccade, the electrical signals in the hippocampus display a more coherent rhythm.

The rhythm reset a saccade imposes may be a way to ensure the hippocampus is receptive to new sensory information, the researchers propose.  
“The eye movements are acting like the conductor of the hippocampal orchestra,” Jutras says, “The phase reset might be a mechanism to ensure the ongoing theta rhythm is in sync with incoming visual information.”

Scientists have previously hypothesized that theta oscillations in the hippocampus set the stage for memory formation. The researchers tested this idea by presenting the monkeys each image twice during a viewing session. Because all primates have an innate preference for novelty, monkeys tend to spend a longer time looking at new images and less time looking at repeated ones. The researchers inferred that the monkeys had a stronger memory of a given picture if, upon second viewing, they looked through it quickly. The theta rhythm reset was more consistent during the viewing of images that the monkeys remembered well.

"Based on this finding, we concluded that this resetting of the theta rhythm is an important part of the memory process," Jutras says.

"This study has given us a better understanding of the function of the hippocampal theta rhythm, which has been well characterized in rodents but isn’t well understood in primates," he says. "A future goal is to investigate the relationship between hippocampal theta and eye movements during memory formation and navigation in humans. This could be possible with epilepsy patients who undergo monitoring of hippocampal activity as part of their treatment."

(Source: news.emory.edu)

Neuroimaging improves understanding of eating disorder

In a spacious hotel room not far from the beach in La Jolla, Calif., Kelsey Heenan gripped her fiancé’s hand. Heenan, a 20-year-old anorexic woman, couldn’t believe what she was hearing. Walter Kaye, director of the eating disorders program at the University of California, San Diego, was telling a handful of rapt patients and their family members what the latest brain imaging research suggested about their disorder.

It’s not your fault, he told them.

Heenan had always assumed that she was to blame for her illness. Kaye’s data told a different story. He handed out a pile of black-and-white brain scans — some showed the brains of healthy people, others were from people with anorexia nervosa. The scans didn’t look the same. “People were shocked,” Heenan says. But above all, she remembers, the group seemed to sigh in relief, breathing out years of buried guilt about the disorder. “It’s something in the way I was wired — it’s something I didn’t choose to do,” Heenan says. “It was pretty freeing to know that there could be something else going on.”

Years of psychological and behavioral research have helped scientists better understand some signs and triggers of anorexia. But that knowledge hasn’t straightened out the disorder’s tangled roots, or pointed scientists to a therapy that works for everyone. “Anorexia has a high death rate, it’s expensive to treat and people are chronically ill,” says Kaye.

Kaye’s program uses a therapy called family-based treatment, or FBT, to teach adolescents and their families how to manage anorexia. A year after therapy, about half of the patients treated with FBT recover. In the world of eating disorders, that’s success: FBT is considered one of the very best treatments doctors have. To many scientists, that just highlights how much about anorexia remains unknown.

Kaye and others are looking to the brain for answers. Using brain imaging tools and other methods to explore what’s going on in patients’ minds, researchers have scraped together clues that suggest anorexics are wired differently than healthy people. The mental brakes people use to curb impulsive instincts, for example, might get jammed in people with anorexia. Some studies suggest that just a taste of sugar can send parts of the brain barrelling into overdrive. Other brain areas appear numb to tastes — and even sensations such as pain. For people with anorexia, a sharp pang of hunger might register instead as a dull thud.

The mishmash of different brain imaging data is just beginning to highlight the neural roots of anorexia, Kaye says. But because starvation physically changes the brain, researchers can run into trouble teasing out whether glitchy brain wiring causes anorexia, or vice versa. Still, Kaye thinks understanding what’s going on in the brain may spark new treatment ideas. It may also help the eating disorder shake off some of its noxious stereotypes.

“One of the biggest problems is that people do not take this disease seriously,” says James Lock, an eating disorders researcher at Stanford University who cowrote the book on family-based treatment. “No one gets upset at a child who has cancer,” he says. “If the treatment is hard, parents still do it because they know they need to do it to make their child well.”

Pop culture often paints anorexics as willful young women who go on diets to be beautiful, he says. But, “you can’t just choose to be anorexic,” Lock adds. “The brain data may help counteract some of the mythology.”

Beyond dieting

A society that glamorizes thinness can encourage unhealthy eating behaviors in kids, scientists have shown. A 2011 study of Minnesota high school students reported that more than half of girls had dieted within the past year. Just under a sixth had used diet pills, vomiting, laxatives or diuretics.

But a true eating disorder goes well beyond an unhealthy diet. Anorexia involves malnutrition, excessive weight loss and often faulty thinking about one of the body’s most basic drives: hunger. The disorder is also rare. Less than 1 percent of girls develop anorexia. The disease crops up in boys too, but adolescent girls — especially in wealthy countries such as the U.S., Australia and Japan — are most likely to suffer from the illness.

As the disease progresses, people with anorexia become intensely afraid of getting fat and stick to extreme diets or exercise schedules to drop pounds. They also misjudge their own weight. Beyond these diagnostic hallmarks, patients’ symptoms can vary. Some refuse to eat, others binge and purge. Some live for years with the illness, others yo-yo between weight gain and loss. Though most anorexics gain back some weight within five years of becoming ill, anorexia is the deadliest of all mental disorders.

Though anorexia tends to run in families, scientists haven’t yet hammered out the suite of genes at play. Some individuals are particularly vulnerable to developing an eating disorder. In these people, stressful life changes, such as heading off to college, can tip the mental scales toward anorexia.

For decades, scientists have known that anorexic children behave a little differently. In school and sports, anorexic kids strive for perfection. Though Heenan, a former college basketball player, didn’t notice her symptoms creeping in until the end of high school, she remembers initiating strict practice regimens as a child. Starting in second grade, Heenan spent hours perfecting her jump shot, shooting the ball again and again until she had the technique exactly right — until her form was flawless.

“It’s very rare for me to see a person with anorexia in my office who isn’t a straight-A student,” Lock says. Even at an early age, people who later develop the eating disorder tend to exert an almost superhuman ability to practice, focus or study. “They will work and work and work,” says Lock. “The problem is they don’t know when to stop.”

In fact, many scientists think anorexics’ brains might be wired for willpower, for good and ill. Using new imaging tools that let scientists watch as a person’s mental gears grind through different tasks, researchers are starting to pin down how anorexic brains work overtime.

Different wiring: Studies of the brains of people with anorexia have revealed a number of complex brain circuits that show changes in activity compared with healthy people. Medical RF, adapted by M. Atarod

Control signs

To glimpse the circuits that govern self-control, experimental neuropsychologist Samantha Brooks uses functional magnetic resonance imaging, or fMRI, a tool that measures and maps brain activity. Last year, she and colleagues scanned volunteers as they imagined eating high-calorie foods, such as chocolate cake and French fries, or using inedible objects such as clothespins piled on a plate. One result gave Brooks a jolt. A center of self-control in anorexics’ brains sprung to life when the volunteers thought about food — but only in the women who severely restricted their calories, her team reported March 2012 in PLOS ONE.

The control center, two golf ball–sized chunks of tissue called the dorsolateral prefrontal cortex, or DLPFC, helps stamp out primitive urges. “They put a brake on your impulsive behaviors,” says Brooks, now at the University of Cape Town in South Africa.

For Brooks, discovering the DLPFC data was like finding a tiny vein of gold in a heap of granite. The control center could be the nugget that reveals how anorexics clamp down on their appetites. So she and her colleagues devised an experiment to test anorexics’ DLPFC. Using a memory task known to engage the brain region, the researchers quizzed volunteers while showing them subliminal images. The quizzes tested working memory, the mental tool that lets people hold  phone numbers in their heads while hunting for a pen and paper. Compared with healthy people, anorexics tended to get more answers right, Brooks’ team wrote June 2012 in Consciousness and Cognition. “The patients were really good,” Brooks says. “They hardly made any mistakes.”

A turbocharged working memory could help anorexics hold on to rules they set for themselves about food. “It’s like saying ‘I will only eat a salad at noon, I will only eat a salad at noon,’ over and over in your mind,” says Brooks. These mantras may become so ingrained that an anorexic person can’t escape them.

But looking at subliminal images of food distracted anorexics from the memory task. “Then they did just as well as the healthy people,” Brooks says. The results suggest that anorexic people might tap into their DLPFC control circuits when faced with food.

James Lock has also seen signs of self-control circuits gone awry in people with eating disorders. In 2011, he and colleagues scanned the brains of teenagers with different eating disorders while signaling them to push a button. While volunteers lay inside the fMRI machine, researchers flashed pictures of different letters on an interior screen. For every letter but “X,” Lock’s group told the teens to push a button. During the task, anorexic teens who obsessively cut calories tended to have more active visual circuits than healthy teens or those with bulimia, a disorder that compels people to binge and purge. The result isn’t easy to explain, says Lock. “Anorexics may just be more focused in on the task.”

Bulimics’ brains told a simpler story. When teens with bulimia saw the letter “X,” broad swaths of their brains danced with activity — more so than the healthy or calorie-cutting anorexic volunteers, Lock’s team reported in the American Journal of Psychiatry. For bulimics, controlling the impulse to push the button may take more brain power than for others, Lock says.

Though the data don’t reveal differences in self-control between anorexics and healthy people, Lock thinks that anorexics’ well-documented ability to swat away urges probably does have signatures in the brain. He notes that his study was small, and that the “healthy” people he used as a control group might have shared similarities with anorexics. “The people who tend to volunteer are generally pretty high performers,” he says. “The chances are good that my controls are a little bit more like anorexics than bulimics.”

Still, Lock’s results offered another flicker of proof that people with eating disorders might have glitches in their self-control circuits. A tight rein on urges could help steer anorexics toward illness, but the parts of their brain tuned into rewards, such as sugary snacks, may also be a little off track.

Sugar low

When an anorexic woman unexpectedly gets a taste of sugar (yellow) or misses out on it (blue), her brain’s reward circuitry shows more activity than a healthy-weight or obese woman’s. Anorexics’ reward-processing systems may be out of order. Credit: G. Frank et al/ Neuropsychopharmacology 2012

For many anorexics, food just doesn’t taste very good. A classic symptom of the disorder is anhedonia, or trouble experiencing pleasure. Parts of Heenan’s past reflect the symptom. When she was ill, she had trouble remembering favorite dishes from childhood, for example — a blank spot common to anorexics. “I think I enjoyed some things,” she says. Beyond frozen yogurt, she can’t really rattle off a list.

After Heenan started seriously restricting her calories in college, only one aspect of food made her feel satisfied. Skipping, rather than eating, meals felt good, she says. Some of Heenan’s symptoms may have stemmed from frays in her reward wiring, the brain circuitry connecting food to pleasure. In the past few years, researchers have found that the chemicals coursing through healthy people’s reward circuits aren’t quite the same in anorexics. And studies in rodents have linked chemical changes in reward circuitry to under- and overeating.

To find out whether under- and overweight people had altered brain chemistry, eating disorder researcher Guido Frank of the University of Colorado Denver studied anorexic, healthy-weight and obese women. He and his colleagues trained volunteers to link images, such as orange or purple shapes, with the taste of a sweet solution, slightly salty water or no liquid. Then, the researchers scanned the women’s brains while showing them the shapes and dispensing tiny squirts of flavors. But the team threw in a twist: Sometimes the flavors didn’t match up with the right images.

When anorexics got an unexpected hit of sugar, a surge of activity bloomed in their brains. Obese people had the opposite response: Their brains didn’t register the surprise. Healthy-weight women fit somewhere in the middle, Frank’s team reported August 2012, in Neuropsychopharmacology. While obese people might not be sensitive to sweets anymore, a little sugar rush goes a long way for anorexics. “It’s just too much stimulation for them,” Frank says.

One of the lively regions in anorexics’ brains was the ventral striatum, a lump of nerve cells that’s part of a person’s reward circuitry. The lump picks up signals from dopamine, a chemical that rushes in when most people see a sugary treat.

Frank says that it’s possible cutting calories could sculpt a person’s brain chemistry, but he thinks some young people are just more likely to become sugar-sensitive than others. Frank suspects anorexics’ dopamine-sensing equipment might be out of alignment to begin with. And he may be onto something. Recently, researchers in Kaye’s lab at UCSD showed that the same chemical that makes people perk up when a coworker brings in a box of doughnuts might actually trigger anxiety in anorexics.

Mixed signals

Usually a rush of dopamine triggers euphoria or a boost of energy, says Ursula Bailer, a psychiatrist and neuroimaging researcher at UCSD. Anorexics don’t seem to pick up those good feelings. 

When Bailer and colleagues gave volunteers amphetamine, a drug known to trigger dopamine release, and then asked them to rate their feelings, healthy people stuck to a familiar script. The drug made them feel intensely happy, Bailer’s team described March 2012 in the International Journal of Eating Disorders. Researchers linked the volunteers’ happy feelings to a wave of dopamine flooding the brain, using an imaging technique to track the chemical’s levels.

But anorexics said something different. “People with anorexia didn’t feel euphoria — they got anxious,” Bailer says. And the more dopamine coursing through anorexics’ brains, the more anxious they felt. Anorexics’ reaction to the chemical could help explain why they steer clear of food — or at least foods that healthy people find tempting. “Anorexics don’t usually get anxious if you give them a plate of cucumbers,” Bailer says.

Beyond the anxiety finding, one other aspect of the study sticks out: Instead of examining sick patients, Bailer, Kaye and colleagues recruited women who had recovered from anorexia. By studying people whose brains are no longer starving, Kaye’s team hopes to sidestep the chicken-and-egg question of whether specific brain signatures predispose people to anorexia or whether anorexia carves those signatures in the brain.

Though Kaye says that there’s still a lot scientists don’t know about anorexia, he’s convinced it’s a disorder that starts in the brain. Compared with healthy children, anorexic children’s brains are getting different signals, he says. “Parents have to realize that it’s very hard for these kids to change.”

Kaye thinks imaging data can help families reframe their beliefs about anorexia, which might help them handle tough treatments. He thinks the data can also offer new insights into therapies tailored for anorexics’ specific traits.

Sensory underload

One trait Kaye has focused on is anorexics’ sense of awareness of their bodies. Peel back the outer lobes of the brain by the temples, and the bit that handles body awareness pops into view. These regions, little islands of tissue called the insula, are one of the first brain areas to register pain, taste and other sensations. When people hold their breath, for example, and feel the panicky claws of air hunger, “the insula lights up like crazy,” Kaye says.

Kaye and colleagues have shown that the insulas of people with anorexia seem to be somewhat dulled to sensations. In a recent study, his team strapped heat-delivering gadgets to volunteers’ arms and cranked the devices to painfully hot temperatures while measuring insula activity via fMRI.

Compared with healthy volunteers, bits of recovered anorexics’ insulas dimmed when the researchers turned up the heat. But when researchers simply warned that pain was coming, other parts of the brain region flared brightly, Kaye’s team reported in January in the International Journal of Eating Disorders. For people who have had anorexia, actually feeling pain didn’t seem as bad as anticipating it. “They don’t seem to be sensing things correctly,” says Kaye.

If anorexics can’t detect sensations like pain properly, they may also have trouble picking up other signals from the body, such as hunger. Typically when people get hungry, their insulas rev up to let them know. And in healthy hungry people, a taste of sugar really gets the insula excited. For anorexics, this hunger-sensing part of the brain seems numb. Parts of the insula barely perked up when recovered anorexic volunteers tasted sugar, Kaye’s team showed this June in the American Journal of Psychiatry. The findings “may help us understand why people can starve themselves and not get hungry,” Kaye says.

Though the brain region that tells people they’re hungry might have trouble detecting sweet signals, some reward circuits seem to overreact to the same cues. Combined with a tendency to swap happiness for anxiety, and a mental vise grip on behavior, anorexics might have just enough snags in their brain wiring to tip them toward disease.

Now, Kaye’s group hopes to tap neuroimaging data for new treatment ideas. One day, he thinks doctors might be able to help anorexics “train” their insulas using biofeedback. With real-time brain scanning, patients could watch as their insulas struggle to pick up sugar signals, and then practice strengthening the response. More effective treatment options could potentially spare anorexics the relapses many patients suffer.

Heenan says she’s one of the lucky ones. Four years have passed since she first saw the anorexic brain images at UCSD. In the months following her treatment, Heenan and her family worked together to rebuild her relationship with food. At first, her fiancé picked out all her meals, but step by step, Heenan earned autonomy over her diet. Today, Heenan, a coordinator for Minneapolis’ public schools, is married and has a new puppy. “Life can be good,” she says. “Life can be fun. I want other people to know the freedom that I do.”

Searching for treatments

The bowl of pasta sitting in front of Kelsey Heenan didn’t look especially scary.

Spaghetti, chopped asparagus and chunks of chicken glistened in an olive oil sauce. Usually, such savory fare might make a person’s mouth water. But when Heenan’s fiancé served her a portion, she started sobbing. “You can’t do this to me,” she told him. “I thought you loved me!”

Heenan was confronting her “fear foods” at the Eating Disorders Center for Treatment and Research at UCSD. Therapists in her treatment program, Intensive Multi-Family Therapy, spend five days teaching anorexic patients and families about the disorder and how to encourage healthy eating. “There’s no blame,” says Christina Wierenga, a clinical neuropsychologist at UCSD. “The focus is just on having the parent refeed the child.” Therapists lay out healthy meals and portion sizes for teens, bolster parents’ self-confidence and hammer home the dangers of not eating. Heenan compares the experience to boot camp. But by the end of her time at the center, she says, “I was starting to see glimpses of what life could be like as a healthy person.”

Treatment options for anorexia include a broad mix of behavioral and medication-based therapies. Most don’t work very well, and many lack the support of evidence-based trials. Hospitalizing patients can boost short-term weight gain, “but when people go home they lose all the weight again,” says Stanford University’s James Lock, one of the architects of family-based treatment. That treatment is currently considered the most effective therapy for adolescent anorexics.

In a 2010 clinical trial, half of teens who underwent FBT maintained a normal weight a year after therapy. In contrast, only a fifth of teens treated with adolescent-focused individual therapy, which aims to help kids cope with emotions without using starvation, hit the healthy weight goal.

Few good options exist for adult anorexics, a group notorious for dropping out of therapy. New work hints that cognitive remediation therapy, or CRT, which uses cognitive exercises to change anorexics’ behaviors, has potential. After two months of CRT, only 13 percent of patients abandoned treatment, and most regained some weight, Lock and colleagues reported in the April International Journal of Eating Disorders. Researchers still need to find out, however, if CRT helps patients keep weight on long-term.

(Source: sciencenews.org)

Next-generation drugs designed to fight Alzheimer’s disease look very promising. Scientists have unveiled the mechanisms behind two classes of compound currently being tested in clinical trials. They have also identified a likely cause of early-onset hereditary forms of the disease.

The future is looking good for drugs designed to combat Alzheimer’s disease. EPFL scientists have unveiled how two classes of drug compounds currently in clinical trials work to fight the disease. Their research suggests that these compounds target the disease-causing peptides with high precision and with minimal side-effects. At the same time, the scientists offer a molecular explanation for early-onset hereditary forms of Alzheimer’s, which can strike as early as thirty years of age. The conclusions of their research, which has been published in the journal Nature Communications, are very encouraging regarding the future of therapeutic means that could keep Alzheimer’s disease in check.

Alzheimer’s disease is characterized by an aggregation of small biological molecules known as amyloid peptides. We all produce these molecules; they play an essential antioxidant role. But in people with Alzheimer’s disease, these peptides aggregate in the brain into toxic plaques – called “amyloid plaques” – that destroy the surrounding neurons.

The process starts with a long protein, “APP”, which is located across the neuron’s membrane. This protein is cut into several pieces by an enzyme, much like a ribbon is cut by scissors. The initial cut generates a smaller intracellular protein that plays a useful role in the neuron. Another cut releases the rest of APP outside the cell – this part is the amyloid peptide.

For reasons not yet well understood, APP protein can be cut in several different places, producing amyloid peptides that are of varying lengths. Only the longer forms of the amyloid peptide carry the risk of aggregating into plaques, and people with Alzheimer’s disease produce an abnormally high number of these.

A favorite Alzheimer’s target: gamma secretase

The two next-generation classes of compound that are currently in clinical trials target an enzyme that cuts APP, known as gamma secretase. Until now, our understanding of the mechanism involved has been lacking. But with this work, the EPFL researchers were able to shed some more light on it by determining how the drug compounds affect gamma secretase and its cutting activity.

In most forms of Alzheimer’s, abnormally large quantities of the long amyloid peptide 42 – named like that because it contains 42 amino acids – are formed. The drug compounds change the location where gamma secretase cuts the APP protein, thus producing amyloid peptide 38 instead of 42, which is shorter and does not aggregate into neurotoxic plaques.

Compared to previous therapeutic efforts, this is considerable progress. In 2010, Phase III clinical trials had to be abandoned, because the compound being tested inhibited gamma-secretase’s function across the board, meaning that the enzyme was also deactivated in essential cellular differentiation processes, resulting to side-effects like in gastrointestinal bleeding and skin cancer.

“Scientists have been trying to target gamma secretase to treat Alzheimer’s for over a decade,” explains Patrick Fraering, senior author on the study and Merck Serono Chair of Neurosciences at EPFL. “Our work suggests that next-generation molecules, by modulating rather than inhibiting the enzyme, could have few, if any, side-effects. It is tremendously encouraging.”

New insights into hereditary forms of the disease

During their investigation, the scientists also identified possible causes behind some hereditary forms of Alzheimer’s disease. Early-onset Alzheimer’s can appear as early as thirty years of age, with a life expectancy of only a few years. In vitro experiments and numerical simulations show that in early-onset patients, mutations in the APP protein gene modify the way by which APP is cut by the gamma-secretase enzyme. This results in overproduction of amyloid peptide 42, which then aggregates into amyloid plaques.

This research illuminates much that is unknown about Alzheimer’s disease. “We have obtained extraordinary knowledge about how gamma secretase can be modulated,” explains co-author Dirk Beher, scientific chief officer of Asceneuron, a spin-off of Merck Serono, the biopharmaceutical division of Merck KGaA, Darmstadt, Germany. “This knowledge will be invaluable for developing even better targeted drugs to fight the disease.”

(Source: actu.epfl.ch)

Scientists from the Florida campus of The Scripps Research Institute have described findings that could enable the development of more effective drugs for addiction with fewer side effects.

The study, published in the August 2, 2013 issue of the Journal of Biological Chemistry, showed in a combination of cell and animal studies that one active compound maintains a strong bias towards a single biological pathway, providing insight into what future drugs could look like.

The compound examined in the study, known as 6’- guanidinonaltrindole (6’-GNTI), targets the kappa opioid receptor (KOR). Located on nerve cells, KOR plays a role in the release of dopamine, a neurotransmitter that plays a key role in drug addiction. Drugs of abuse often cause the brain to release large amounts of dopamine, flooding the brain’s reward system and reinforcing the addictive cycle.

“There are a number of drug discovery efforts ongoing for KOR,” said Laura Bohn, a TSRI associate professor, who led the study. “The ultimate question is how this receptor should be acted upon to achieve the best therapeutic effects. Our study identifies a marker that shows how things normally happen in live neurons—a critically important secondary test to evaluate potential compounds.”

While KOR has become the focus for drug discovery efforts aimed at treating addiction and mood disorders, KOR can react to signals that originate independently from multiple biological pathways, so current drug candidates targeting KOR often produce unwanted side effects. Compounds that activate KOR can decrease the rewarding effects of abused drugs, but also induce sedation and depression.

The new findings, from studies of nerve cells in the striatum (an area of the brain involved in motor activity and higher brain function), reveal a point on the KOR signaling pathway that may prove to be an important indicator of whether drug candidates can produce effects similar to the natural biological effects.

“Standard screening assays can catch differences but those differences may not play out in live tissue,” Bohn noted. “Essentially, we have shown an important link between cell-based screening assays and what occurs naturally in animal models.”

(Source: scripps.edu)