How Ketamine Changes the Depressed Patient’s Brain

By Simon Makin

The Food and Drug Administration’s approval last month of a depression treatment based on ketamine generated headlines, in part, because the drug represents a completely new approach for dealing with a condition the World Health Organisation has labelled the leading cause of disability worldwide. The FDA’s approval marks the first genuinely new type of psychiatric drug—for any condition—to be brought to market in more than 30 years.

Although better known as a party drug, the anesthetic ketamine has spurred excitement in psychiatry for almost 20 years, since researchers first showed that it alleviated depression in a matter of hours. The rapid reversal of symptoms contrasted sharply with the existing set of antidepressants, which take weeks to begin working. Subsequent studies have shown ketamine works for patients who have failed to respond to multiple other treatments, and so are deemed “treatment-resistant.”

Despite this excitement, researchers still don’t know exactly how ketamine exerts its effects. A leading theory proposes that it stimulates regrowth of synapses (connections between neurons), effectively rewiring the brain. Researchers have seen these effects in animals’ brains, but the exact details and timing are elusive.

A new study, from a team led by neuroscientist and psychiatrist Conor Liston at Weill Cornell Medicine, has confirmed that synapse growth is involved, but not in the way many researchers were expecting. Using cutting-edge technology to visualize and manipulate the brains of stressed mice, the study reveals how ketamine first induces changes in brain circuit function, improving “depressed” mice’s behavior within three hours, and only later stimulating regrowth of synapses.

As well as shedding new light on the biology underlying depression, the work suggests new avenues for exploring how to sustain antidepressant effects over the long term. “It’s a remarkable engineering feat, where they were able to visualize changes in neural circuits over time, corresponding with behavioral effects of ketamine,” says Carlos Zarate, chief of the Experimental Therapeutics and Pathophysiology Branch at the National Institute of Mental Health, who was not involved in the study. “This work will likely set a path for what treatments should be doing before we move them into the clinic.”

Another reason ketamine has researchers excited is that it works differently than existing antidepressants. Rather than affecting one of the “monoamine” neurotransmitters (serotonin, norepinephrine, and dopamine), as standard antidepressants do, it acts on glutamate, the most common chemical messenger in the brain. Glutamate plays an important role in the changes synapses undergo in response to experiences that underlie learning and memory. That is why researchers suspected such “neuroplasticity” would lie at the heart of ketamine’s antidepressant effects.

Ketamine’s main drawback is its side effects, which include out-of-body experiences, addiction and bladder problems. It is also not a “cure.” The majority of recipients who have severe, difficult-to-treat depression will ultimately relapse. A course of multiple doses typically wears off within a few weeks to months. Little is known about the biology underlying depressive states, remission and relapse. “A big question in the field concerns the mechanisms that mediate transitions between depression states over time,” Liston says. “We were trying to get a better handle on that in the hopes we might be able to figure out better ways of preventing depression and sustaining recovery.”

Chronic stress depletes synapses in certain brain regions, notably the medial prefrontal cortex (mPFC), an area implicated in multiple aspects of depression. Mice subjected to stress display depressionlike behaviors, and with antidepressant treatment, they often improve. In the new study, the researchers used light microscopes to observe tiny structures called spines located on dendrites (a neuron’s “input” wires) in the mPFC of stressed mice. Spines play a key role because they form synapses if they survive for more than a few days.

For the experiment, some mice became stressed when repeatedly restrained, others became so after they were administered the stress hormone corticosterone. “That’s a strength of this study,” says neuroscientist Anna Beyeler, of the University of Bordeaux, France, who was not involved in the work, but wrote an accompanying commentary article in Science. “If you’re able to observe the same effects in two different models, this really strengthens the findings.” The team first observed the effects of subjecting mice to stress for 21 days, confirming that this resulted in lost spines. The losses were not random, but clustered on certain dendrite branches, suggesting the damage targets specific brain circuits.

The researchers then looked a day after administering ketamine and found that the number of spines increased. Just over half appeared in the same location as spines that were previously lost, suggesting a partial reversal of stress-induced damage. Depressionlike behaviors caused by the stress also improved. The team measured brain circuit function in the mPFC, also impaired by stress, by calculating the degree to which activity in cells was coordinated, a measure researchers term “functional connectivity.” This too improved with ketamine.

When the team looked closely at the timing of all this, they found that improvements in behavior and circuit function both occurred within three hours, but new spines were not seen until 12 to 24 hours after treatment. This suggests that the formation of new synapses is a consequence, rather than cause, of improved circuit function. Yet they also saw that mice who regrew more spines after treatment performed better two to seven days later. “These findings suggest that increased ensemble activity contributes to the rapid effects of ketamine, while increased spine formation contributes to the sustained antidepressant actions of ketamine,” says neuroscientist Ronald Duman, of the Yale School of Medicine, who was not involved in the study. Although the molecular details of what happens in the first hours are not yet fully understood, it seems a restoration of coordinated circuit activity occurs first; this is then entrenched by neuroplasticity effects in synapses, which then maintain behavioral benefits over time.

To prove that new synapses were a cause of antidepressant effects, rather than just coinciding with the improved behaviors, the team used a newly developed optogenetic technique, which allowed them to eliminate newly formed spines using light. Optogenetics works by introducing viruses that genetically target cells, causing them to produce light-sensitive proteins. In this case, the protein is expressed in newly formed synapses, and exposure to blue light causes the synapse to collapse. The researchers found that eliminating newly formed synapses in ketamine-treated mice abolished some of the drug’s positive effects, two days after treatment, confirming that new synapses are needed to maintain benefits. “Many mechanisms are surely involved in determining why some people relapse and some don’t,” Liston says, ” but we think our work shows that one of those involves the durability of these new synapses that form.”

And Liston adds: “Our findings open up new avenues for research, suggesting that interventions aimed at enhancing the survival of these new synapses might be useful for extending ketamine’s antidepressant effects.” The implication is that targeting newly formed spines might be useful for maintaining remission after ketamine treatment. “This is a great question and one the field has been considering,” Duman says. “This could include other drugs that target stabilization of spines, or behavioral therapies designed to engage the new synapses and circuits, thereby strengthening them.”

The study used three behavioral tests: one involving exploration, a second a struggle to escape, and a third an assessment of how keen the mice are on a sugar solution. This last test is designed to measure anhedonia—a symptom of depression in which the ability to experience pleasure is lost. This test was unaffected by deleting newly formed spines, suggesting that the formation of new synapses in the mPFC is important for some symptoms, such as apathy, but not others (anhedonia)—and that different aspects of depression involve a variety of brain circuits.

These results could relate to a study published last year that found activity in another brain region, the lateral habenula, is crucially involved in anhedonia, and injecting ketamine directly into this region improves anhedonia-related behavior in mice. “We’re slowly identifying specific regions associated with specific behaviors,” Beyeler says. “The factors leading to depression might be different depending on the individual, so these different models might provide information regarding the causes of depression.”

One caveat is that the study looked at only a single dose, rather than the multiple doses involved in a course of human treatment, Zarate says. After weeks of repeated treatments, might the spines remain, despite a relapse, or might they dwindle, despite the mice still doing well? “Ongoing effects with repeated administration, we don’t know,” Zarate says. “Some of that work will start taking off now, and we’ll learn a lot more.” Of course, the main caution is that stressed mice are quite far from humans with depression. “There’s no real way to measure synaptic plasticity in people, so it’s going to be hard to confirm these findings in humans,” Beyeler says.

https://www.scientificamerican.com/article/behind-the-buzz-how-ketamine-changes-the-depressed-patients-brain/

FDA Clears Unique Medical Device for Treatment of Anxiety, Depression, and Insomnia

The Food and Drug Administration (FDA) has approved a new cranial electrotherapy stimulator (CES) device for the treatment of anxiety, depression, and insomnia.

The Cervella Cranial Electrotherapy Stimulator by Innovative Neurological Devices is operated using noise-cancelling, Bluetooth-enabled headphones and an app. The device delivers a low-level, constant current to the patient’s cranium via a pair of conductive electrodes incorporated into ear pads of the headphones.

Patients will need a prescription from a licensed healthcare provider in order to purchase the device, which will cost $695, and is due to launch at the end of March (2019).

“We hope that by incorporating treatment electrodes into a noise-cancelling headset, patient compliance will significantly increase and, consequently, treatment outcomes will improve,” said Bart Waclawik, President and CEO of Innovative Neurological Devices. “Also, by making the Cervella device appear indistinguishable from ordinary over-ear headphones, patients will have the freedom to use the device in anxiety-inducing situations without curious looks from onlookers.”

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Waclawik added that patients will be able to share treatment data with providers through the app, which provides automated data recordings and treatment reminders.

For more information visit Cervella.us.

FDA approves first drug for postpartum depression

By Elizabeth Chuck and Lauren Dunn

The intrusive thoughts started weeks after Stephanie Hathaway gave birth: an overwhelming feeling that her daughter deserved a better mother; that her husband deserved a better wife; that her future was hopeless.

“They just played on repeat in my head,” Hathaway, 33, of South Glastonbury, Connecticut, said. “I was holding my baby one night, and my husband was at a meeting, and I just thought, ‘Oh, my goodness. If I put the baby down, I might hurt myself.’”

Hathaway was diagnosed with postpartum depression — the intense sadness, anxiety or despair that occurs within the first year after giving birth, according to the Centers for Disease Control and Prevention. It affects about one in nine women, although the rate may be as high as one in every five women, the CDC finds.

Hathaway’s doctor put her on antidepressants, which helped some, but it took two weeks for the medication to kick in, and even longer until her doctor found the appropriate dosage for her. As she waited for relief, Hathaway found herself struggling to bond with her newborn, Hadley, who is now 4.

“It’s heartbreaking,” Hathaway, who had never suffered from depression before and is now a mother to two girls, said. “That’s not what I expected to feel.”

Up until this point, new mothers experiencing postpartum depression have been prescribed the same antidepressants used for treating depression in the general population, such as selective serotonin reuptake inhibitors. The drugs can take weeks to take effect, and do not address the hormonal changes that women go through during and after pregnancy.

But on Tuesday, the Food and Drug Administration approved the first drug specifically developed for postpartum depression, called brexanolone, or Zulresso.

Brexanolone is novel because it has a synthetic form of the hormone allopregnanolone, a progesterone derivative, in it. The hormone increases throughout a woman’s pregnancy and then plummets after she gives birth, a possible contributor to postpartum depression.

“This can potentially transform women’s lives and that of their families,” said Dr. Steve Kanes, chief medical officer of Sage Therapeutics, the Cambridge, Mass., biopharmaceutical company that developed brexanolone. “It’s not just the mother who suffers when there’s postpartum depression. It’s the newborn. It’s the other people in their family.”

Brexanolone is not a pill. The drug is delivered intravenously over the course of a 60-hour infusion, meaning it must be administered in a medically supervised setting, such as a skilled facility or a hospital, rather than at patients’ homes.

IMPROVEMENT IN JUST 24 HOURS

Clinical trials for the drug were promising — not just in the number of women it helped, but in the near-instantaneous relief that is provided.

In double-blind, placebo-controlled trials, many women with moderate to severe postpartum depression saw a marked improvement of their symptoms within just 24 hours of receiving the drug. That improvement was still present 30 days after the infusion, the length of the trial.

“This is for postpartum depression, but it is a step in understanding how we treat depression more broadly,” said Dr. Samantha Meltzer-Brody, director of the perinatal psychiatry program at the University of North Carolina at Chapel Hill and the academic principal investigator in the brexanolone trials. “We have had the same treatments for depression for 30 years. There’s an enormous need for new, novel ways to treat depression, and to treat it quickly.”

The drug’s approval comes just weeks after the FDA signed off on esketamine, a fast-acting nasal spray that uses the active ingredients in the club drug ketamine, as a treatment for severe depression.

For patients who are depressed, rapid relief is a priority. Hathaway, the Connecticut mother, was again diagnosed with postpartum depression after she gave birth to her second, a girl named Brenley who is now 2. This time, the antidepressants did not help at all, and Hathaway felt herself slipping deeper and deeper into a state of hopelessness.

She participated in a brexanolone trial, and her response was striking. Between hours 12 and 18 of the 60-hour infusion, she noticed her despair had waned.

“I woke up from a nap, and the thoughts were gone. And they never came back,” Hathaway said. “And then hour after hour, I got my energy back. I got my appetite back. I was eating because I was actually hungry, not because people were making me eat.”

A COMMON CONDITION

Postpartum depression afflicts as many as 400,000 women in the United States each year. It can include disturbances in sleep or eating patterns in addition to feelings of sadness or apathy. Affected women are often confused and guilt-ridden about why they are feeling down during what is supposed to be a happy time, said Dr. Christine C. Greves, an obstetrician-gynecologist at Orlando Health Winnie Palmer Hospital for Women and Babies.

“As women, we feel like we were born to have a child, and there’s a white picket fence, and life will be great,” said Greves, who does not have ties to Sage Therapeutics. “Then regular life comes into play. You have a child and then you top that with extensive fatigue, hormones, expectations that just can’t be met. It’s all fantasy until we actually have the baby. And then you do feel guilty, because we all want to be Super Mom.”

In the past decade, experts say, there has been more awareness about postpartum depression and more efforts among obstetricians and pediatricians to screen mothers for it.

But having a drug specifically aimed at treating postpartum depression will be one of the most significant steps toward removing any stigma still associated with the condition, said Dr. Kimberly Yonkers, professor of psychiatry, epidemiology and obstetrics, gynecology and reproductive sciences at the Yale School of Medicine.

“It does women a service because it really brings attention to a major medical problem and provides legitimacy, and hopefully will encourage people, whether they use this medication or not, to seek and obtain treatment,” said Yonkers, who does not have ties to the drug company. “We’re all thrilled about that.”

SOME SIDE EFFECTS, AND A HEFTY PRICE TAG

The most common side effects during the brexanolone trial were drowsiness and dizziness. The drug is not believed to have any long-term safety concerns. Kanes, Sage Therapeutics’ chief medical officer, said he expects it will be deemed safe for all mothers, including breastfeeding mothers, but the company is waiting for an FDA ruling on breastfeeding.

The drug comes with a hefty price tag: Sage says it is expected to cost somewhere between $20,000 to $35,000 for the infusion. That does not include the price of a stay in whatever facility it is administered in. It is not clear yet how much insurance would cover.

Kanes pointed out that while high, the cost is a one-time price.

“That’s such an important piece as to why this is so novel. We’re talking about a single treatment that has durable effects,” he said. “This really is a one-time intervention that gets people on their way. It’s transformative.”

For Hathaway, the brexanolone infusion enabled her to return home and be the mother to her daughters that she had wanted to be before postpartum depression took over.

“It’s given them their mom back,” she said. “This is what it was supposed to be like.”

https://www.nbcnews.com/health/womens-health/fda-approves-first-drug-postpartum-depression-n984521

Scientists Find A Brain Circuit That Could Explain Seasonal Depression


Before light reaches these rods and cones in the retina, it passes through some specialized cells that send signals to brain areas that affect whether you feel happy or sad.

by Jon Hamilton

Just in time for the winter solstice, scientists may have figured out how short days can lead to dark moods.

Two recent studies suggest the culprit is a brain circuit that connects special light-sensing cells in the retina with brain areas that affect whether you are happy or sad.

When these cells detect shorter days, they appear to use this pathway to send signals to the brain that can make a person feel glum or even depressed.

“It’s very likely that things like seasonal affective disorder involve this pathway,” says Jerome Sanes, a professor of neuroscience at Brown University.

Sanes was part of a team that found evidence of the brain circuit in people. The scientists presented their research in November at the Society for Neuroscience meeting. The work hasn’t been published in a peer-reviewed journal yet, but the researchers plan to submit it.

A few weeks earlier, a different team published a study suggesting a very similar circuit in mice.

Together, the studies offer a strong argument that seasonal mood changes, which affect about 1 in 5 people, have a biological cause. The research also adds to the evidence that support light therapy as an appropriate treatment.

“Now you have a circuit that you know your eye is influencing your brain to affect mood,” says Samer Hattar, an author of the mouse study and chief of the section on light and circadian rhythms at the National Institute of Mental Health. The finding is the result of a decades-long effort to understand the elusive link between light and mood. “It is the last piece of the puzzle,” Hattar says.

The research effort began in the early 2000s, when Hattar and David Berson, a professor of neuroscience at Brown University, were studying cells in the retina.

At the time, most scientists thought that when light struck the retina, only two kinds of cells responded: rods and cones. But Hattar and Berson thought there were other light-sensitive cells that hadn’t been identified.

“People used to laugh at us if we say there are other photoreceptors distinct from rods and cones in the retina,” Hattar says.

The skeptics stopped laughing when the team discovered a third kind of photoreceptor that contained a light-sensitive substance called melanopsin not found in rods and cones. (The full name of these cells, if you’re interested, is intrinsically photosensitive retinal ganglion cells, or ipRGCs.) These receptors responded to light but weren’t part of the visual system.

Instead, their most obvious function was keeping the brain’s internal clock in sync with changes in daylight. And many scientists assumed that this circadian function also explained seasonal depression.

“People thought that the only reason you get mood problems is because your clock is misaligned,” Hattar says.

Other potential explanations included speculation that reduced sunlight was triggering depression by changing levels of serotonin, which can affect mood, or melatonin, which plays a role in sleep patterns and mood. But the evidence for either of these possibilities has been weak.

Hattar and Berson were pretty sure there was a better reason. And, after years of searching, they found one.

In September, Hattar’s team published a study about mice suggesting a direct pathway between the third kind of photoreceptor in the retina and brain areas that affect mood.

When these cells were present, an artificially shortened cycle of light and dark caused a version of depression in a mouse. But when the team removed the cells with gene-editing tools, the mouse didn’t become depressed.

Sanes knew about the research, in part because he and Berson are neuroscientists at Brown. And he was so intrigued by the discovery of the new pathway between retina and brain in mice that he decided to see whether something similar was going on in human brains.

Sanes’ team put young adults in an MRI machine and measured their brain activity as they were exposed to different levels of light. This allowed the team to identify brain areas that seemed to be receiving signals from the photoreceptors Hattar and Berson had discovered.

Two of these areas were in the front of the brain. “It’s interesting because these areas seem to be the areas that have been shown in many studies to be involved in depression and other affective disorders,” Sanes says.

The areas also appeared to be part of the same circuit found in mice.

The finding needs to be confirmed. But Hattar is pretty confident that this circuit explains the link between light exposure and mood.

So now he’s trying to answer a new question: Why would evolution produce a brain that works this way?

“You will understand why you would need light to see,” he says, “but why do you need light to make you happy?”

Hattar hopes to find out. In the meantime, he has some advice for people who are feeling low: “Try to take your lunch outside. That will help you adjust your mood.”

https://www.npr.org/sections/health-shots/2018/12/21/678342879/scientists-find-a-brain-circuit-that-could-explain-seasonal-depression

Chronic Bullying Could Actually Reshape The Brains of Teens

by Carly Cassella

Sticks and stones may break your bones, but name-calling could actually change the structure of your brain.

A new study has found that persistent bullying in high school is not just psychologically traumatising, it could also cause real and lasting damage to the developing brain.

The findings are drawn from a long-term study on teenage brain development and mental health, which collected brain scans and mental health questionnaires from European teenagers between the ages of 14 and 19.

Following 682 young people in England, Ireland, France and Germany, the researchers tallied 36 in total who reported experiencing chronic bullying during these years.

When the researchers compared the bullied participants to those who had experienced less intense bullying, they noticed that their brains looked different.

Across the length of the study, in certain regions, the brains of the bullied participants appeared to have actually shrunk in size.

In particular, the pattern of shrinking was observed in two parts of the brain called the putamen and the caudate, a change oddly reminiscent of adults who have experienced early life stress, such as childhood maltreatment.

Sure enough, the researchers found that they could partly explain these changes using the relationship between extreme bullying and higher levels of general anxiety at age 19. And this was true even when controlling for other types of stress and co-morbid depressive symptoms.

The connection is further supported by previous functional MRI studies that found differences in the connectivity and activation of the caudate and putamen activation in those with anxiety.

“Although not classically considered relevant to anxiety, the importance of structural changes in the putamen and caudate to the development of anxiety most likely lies in their contribution to related behaviours such as reward sensitivity, motivation, conditioning, attention, and emotional processing,” explains lead author Erin Burke Quinlan from King’s College London.

In other words, the authors think all of this shrinking could be a mark of mental illness, or at least help explain why these 19-year-olds are experiencing such unusually high anxiety.

But while numerous past studies have already linked childhood and adolescent bullying to mental illness, this is the very first study to show that unrelenting victimisation could impact a teenager’s mental health by actually reshaping their brain.

The results are cause for worry. During adolescence, a young person’s brain is absolutely exploding with growth, expanding at an incredible place.

And even though it’s normal for the brain to prune back some of this overabundance, in the brains of those who experienced chronic bullying, the whole pruning process appears to have spiralled out of control.

The teenage years are an extremely important and formative period in a person’s life, and these sorts of significant changes do not bode well. The authors suspect that as these children age, they might even begin to experience greater shrinkage in the brain.

But an even longer long-term study will need to be done if we want to verify that hunch. In the meantime, the authors are recommending that every effort be made to limit bullying before it can cause damage to a teenager’s brain and their mental health.

This study has been published in Molecular Psychiatry.

https://www.sciencealert.com/chronic-bullying-could-actually-reshape-the-brains-of-teens

40,000 Volunteers Needed for Largest Ever Study of the Genetics of Anxiety and Depression

largest-ever-study-of-genetic-links-to-depression-and-anxiety-launched-309700

The NIHR and King’s College London are calling for 40,000 people diagnosed with depression or anxiety to enrol online for the Genetic Links to Anxiety and Depression (GLAD) Study and join the NIHR Mental Health Bioresource.

Researchers hope to establish the largest ever database of volunteers who can be called up to take part in research exploring the genetic factors behind the two most common mental health conditions – anxiety and depression.

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The GLAD study will make important strides towards better understanding of these disorders and provide a pool of potential participants for future studies, reducing the time-consuming process of recruiting patients for research.

Research has shown 30-40% of the risk for both depression and anxiety is genetic and 60-70% due to environmental factors. Only by having a large, diverse group of people available for studies will researchers be able to determine how genetic and environmental triggers interact to cause anxiety and depression.

Leader of the GLAD study and the NIHR Mental Health BioResource, Dr Gerome Breen of King’s College London, said: “It’s a really exciting time to become involved in mental health research, particularly genetic research which has made incredible strides in recent years – we have so far identified 46 genetic links for depression and anxiety.

“By recruiting 40,000 volunteers willing to be re-contacted for research, the GLAD Study will take us further than ever before. It will allow researchers to solve the big unanswered questions, address how genes and environment act together and help develop new treatment options.”

The GLAD Study, a collaboration between the NIHR BioResource and King’s College London, has been designed to be particularly accessible, with a view to motivating more people to take part in mental health research.

Research psychologist and study lead Professor Thalia Eley, King’s College London, said: “We want to hear from all different backgrounds, cultures, ethnic groups and genders, and we are especially keen to hear from young adults. By including people from all parts of the population, what we learn will be relevant to everyone. This is a unique opportunity to participate in pioneering medical science.”

https://www.nihr.ac.uk/news/nihr-launches-largest-ever-study-of-genetic-links-to-depression-and-anxiety/9201

New tiny sensors track dopamine in the brain for more than a year, and could be useful for monitoring patients with Parkinson’s and other diseases.

Mit-Dopamine-Tracking_0

By Anne Trafton

Dopamine, a signaling molecule used throughout the brain, plays a major role in regulating our mood, as well as controlling movement. Many disorders, including Parkinson’s disease, depression, and schizophrenia, are linked to dopamine deficiencies.

MIT neuroscientists have now devised a way to measure dopamine in the brain for more than a year, which they believe will help them to learn much more about its role in both healthy and diseased brains.

“Despite all that is known about dopamine as a crucial signaling molecule in the brain, implicated in neurologic and neuropsychiatric conditions as well as our abilty to learn, it has been impossible to monitor changes in the online release of dopamine over time periods long enough to relate these to clinical conditions,” says Ann Graybiel, an MIT Institute Professor, a member of MIT’s McGovern Institute for Brain Research, and one of the senior authors of the study.

Michael Cima, the David H. Koch Professor of Engineering in the Department of Materials Science and Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research, and Rober Langer, the David H. Koch Institute Professor and a member of the Koch Institute, are also senior authors of the study. MIT postdoc Helen Schwerdt is the lead author of the paper, which appears in the Sept. 12 issue of Communications Biology.

Long-term sensing

Dopamine is one of many neurotransmitters that neurons in the brain use to communicate with each other. Traditional systems for measuring dopamine — carbon electrodes with a shaft diameter of about 100 microns — can only be used reliably for about a day because they produce scar tissue that interferes with the electrodes’ ability to interact with dopamine.

In 2015, the MIT team demonstrated that tiny microfabricated sensors could be used to measure dopamine levels in a part of the brain called the striatum, which contains dopamine-producing cells that are critical for habit formation and reward-reinforced learning.

Because these probes are so small (about 10 microns in diameter), the researchers could implant up to 16 of them to measure dopamine levels in different parts of the striatum. In the new study, the researchers wanted to test whether they could use these sensors for long-term dopamine tracking.

“Our fundamental goal from the very beginning was to make the sensors work over a long period of time and produce accurate readings from day to day,” Schwerdt says. “This is necessary if you want to understand how these signals mediate specific diseases or conditions.”

To develop a sensor that can be accurate over long periods of time, the researchers had to make sure that it would not provoke an immune reaction, to avoid the scar tissue that interferes with the accuracy of the readings.

The MIT team found that their tiny sensors were nearly invisible to the immune system, even over extended periods of time. After the sensors were implanted, populations of microglia (immune cells that respond to short-term damage), and astrocytes, which respond over longer periods, were the same as those in brain tissue that did not have the probes inserted.

In this study, the researchers implanted three to five sensors per animal, about 5 millimeters deep, in the striatum. They took readings every few weeks, after stimulating dopamine release from the brainstem, which travels to the striatum. They found that the measurements remained consistent for up to 393 days.

“This is the first time that anyone’s shown that these sensors work for more than a few months. That gives us a lot of confidence that these kinds of sensors might be feasible for human use someday,” Schwerdt says.

Paul Glimcher, a professor of physiology and neuroscience at New York University, says the new sensors should enable more researchers to perform long-term studies of dopamine, which is essential for studying phenomena such as learning, which occurs over long time periods.

“This is a really solid engineering accomplishment that moves the field forward,” says Glimcher, who was not involved in the research. “This dramatically improves the technology in a way that makes it accessible to a lot of labs.”

Monitoring Parkinson’s

If developed for use in humans, these sensors could be useful for monitoring Parkinson’s patients who receive deep brain stimulation, the researchers say. This treatment involves implanting an electrode that delivers electrical impulses to a structure deep within the brain. Using a sensor to monitor dopamine levels could help doctors deliver the stimulation more selectively, only when it is needed.

The researchers are now looking into adapting the sensors to measure other neurotransmitters in the brain, and to measure electrical signals, which can also be disrupted in Parkinson’s and other diseases.

“Understanding those relationships between chemical and electrical activity will be really important to understanding all of the issues that you see in Parkinson’s,” Schwerdt says.

The research was funded by the National Institute of Biomedical Imaging and Bioengineering, the National Institute of Neurological Disorders and Stroke, the Army Research Office, the Saks Kavanaugh Foundation, the Nancy Lurie Marks Family Foundation, and Dr. Tenley Albright.

https://news.mit.edu/2018/brain-dopamine-tracking-sensors-0912

A new map of the brain’s serotonin system

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A 3-D rendering of the serotonin system in the left hemisphere of the mouse brain reveals two groups of serotonin neurons in the dorsal raphe that project to either cortical regions (blue) or subcortical regions (green) while rarely crossing into the other’s domain.

As Liqun Luo was writing his introductory textbook on neuroscience in 2012, he found himself in a quandary. He needed to include a section about a vital system in the brain controlled by the chemical messenger serotonin, which has been implicated in everything from mood to movement regulation. But the research was still far from clear on what effect serotonin has on the mammalian brain.

“Scientists were reporting divergent findings,” said Luo, who is the Ann and Bill Swindells Professor in the School of Humanities and Sciences at Stanford University. “Some found that serotonin promotes pleasure. Another group said that it increases anxiety while suppressing locomotion, while others argued the opposite.”

Fast forward six years, and Luo’s team thinks it has reconciled those earlier confounding results. Using neuroanatomical methods that they invented, his group showed that the serotonin system is actually composed of at least two, and likely more, parallel subsystems that work in concert to affect the brain in different, and sometimes opposing, ways. For instance, one subsystem promotes anxiety, whereas the other promotes active coping in the face of challenges.

“The field’s understanding of the serotonin system was like the story of the blind men touching the elephant,” Luo said. “Scientists were discovering distinct functions of serotonin in the brain and attributing them to a monolithic serotonin system, which at least partly accounts for the controversy about what serotonin actually does. This study allows us to see different parts of the elephant at the same time.”

The findings, published online on August 23 in the journal Cell, could have implications for the treatment of depression and anxiety, which involves prescribing drugs such as Prozac that target the serotonin system – so-called SSRIs (selective serotonin reuptake inhibitors). However, these drugs often trigger a host of side effects, some of which are so intolerable that patients stop taking them.

“If we can target the relevant pathways of the serotonin system individually, then we may be able to eliminate the unwanted side effects and treat only the disorder,” said study first author Jing Ren, a postdoctoral fellow in Luo’s lab.

Organized projections of neurons

The Stanford scientists focused on a region of the brainstem known as the dorsal raphe, which contains the largest single concentration in the mammalian brain of neurons that all transmit signals by releasing serotonin (about 9,000).

The nerve fibers, or axons, of these dorsal raphe neurons send out a sprawling network of connections to many critical forebrain areas that carry out a host of functions, including thinking, memory, and the regulation of moods and bodily functions. By injecting viruses that infect serotonin axons in these regions, Ren and her colleagues were able to trace the connections back to their origin neurons in the dorsal raphe.

This allowed them to create a visual map of projections between the dense concentration of serotonin-releasing neurons in the brainstem to the various regions of the forebrain that they influence. The map revealed two distinct groups of serotonin-releasing neurons in the dorsal raphe, which connected to cortical and subcortical regions in the brain.

“Serotonin neurons in the dorsal raphe project to a bunch of places throughout the brain, but those bunches of places are organized,” Luo said. “That wasn’t known before.”

Two parts of the elephant

In a series of behavioral tests, the scientists also showed that serotonin neurons from the two groups can respond differently to stimuli. For example, neurons in both groups fired in response to mice receiving rewards like sips of sugar water but they showed opposite responses to punishments like mild foot shocks.

“We now understand why some scientists thought serotonin neurons are activated by punishment, while others thought it was inhibited by punishment. Both are correct – it just depends on which subtype you’re looking at,” Luo said.

What’s more, the group found that the serotonin neurons themselves were more complex than originally thought. Rather than just transmitting messages with serotonin, the cortical-projecting neurons also released a chemical messenger called glutamate – making them one of the few known examples of neurons in the brain that release two different chemicals.

“It raises the question of whether we should even be calling these serotonin neurons because neurons are named after the neurotransmitters they release,” Ren said.

Taken together, these findings indicate that the brain’s serotonin system is not made up of a homogenous population of neurons but rather many subpopulations acting in concert. Luo’s team has identified two groups, but there could be many others.

In fact, Robert Malenka, a professor and associate chair of psychiatry and behavioral sciences at Stanford’s School of Medicine, and his team recently discovered a group of serotonin neurons in the dorsal raphe that project to the nucleus accumbens, the part of the brain that promotes social behaviors.

“The two groups that we found don’t send axons to the nucleus accumbens, so this is clearly a third group,” Luo said. “We identified two parts of the elephant, but there are more parts to discover.”

https://medicalxpress.com/news/2018-08-brain-serotonin.html

Ketamine shows promise as an effective treatment for adolescents with depression

BY ARISTOS GEORGIOU

Young people suffering from treatment-resistant depression (TRD) showed a significant reduction of their symptoms after being administered ketamine injections, according to a study published in the Journal of Child and Adolescent Psychopharmacology.

Researchers from the University of Minnesota (UM) and the nonprofit Mayo Clinic found that ketamine caused an average decrease of 42 percent on the Children’s Depression Rating Scale (CDRS)—the most widely used rating scale in research trials for assessing the severity of depression and change in depressive symptoms among adolescents.

Ketamine is perhaps best known for being a popular recreational drug and a useful medical anesthetic, but a growing body of research is indicating that the compound could be an effective treatment for depression. Several recent studies have shown that even a single dose in adults can lead to rapid reductions in depressive symptoms. However, relatively little research has been conducted into ketamine’s antidepressant effects in adolescents.

“Adolescence is a very important time for studying depression, first because depression often starts during these years, and second because it is an important time for brain development,” Kathryn Cullen, from the Department of Psychiatry at UM, told Newsweek.

“When adolescent depression persists without successful treatment, it can interfere with achieving important developmental milestones. Finding the right treatment is critical to allow the restoration of healthy brain development and prevent negative outcomes like chronic depression, disability and suicide.”

Unfortunately, about 40 percent of adolescents do not respond to their first intervention and only half of nonresponders respond to the second treatment, according to the researchers.

“Standard antidepressant treatments do not work for everyone and take weeks to months to take effect, a time period when patients are at risk for continued suffering and suicide attempts,” Cullen said. “The field is in need of new treatment options. Ketamine has a very different mechanism of action than standard treatments.”

The latest study involved 13 young people ages 12 to 18 who had failed two previous trials of antidepressants. During a two-week period, the researchers gave them six ketamine infusions.

They found that the treatment was well tolerated, with the participants showing an average decrease in CDRS scores of 42.5 percent. Five of the participants met the criteria for clinical response and remission. Of these, three were still in remission after six weeks, while the remaining two relapsed within two weeks.

According to the scientists, the results demonstrate the potential role for ketamine in treating adolescents with TRD. However, they note that the study was limited by its small sample size, so future research will be needed to confirm these results.

“The purpose of our study was to investigate the effects of ketamine for TRD in younger patients for whom this indication for ketamine administration is not well studied,” Mark Roback, a professor of pediatrics at the University of Minnesota, told Newsweek.

“I think our results show promise for this population, however this study is just a beginning. The study serves to point out the need for further, rigorous, study designed to answer the many questions that remain about ketamine for TRD, such as optimal dosing and route of administration, dosing interval and treatment length, and long-term effects—just to name a few.”

James Stone, a clinical senior lecturer from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, who was not involved in the study, told Newsweek that there is “a lot of potential for the use of ketamine as a second or third line antidepressant where other treatments have failed.”

“Although ketamine is potentially a huge breakthrough in the treatment of depression, we still don’t know about the long-term safety, or about how to keep people well from depression without requiring regular ketamine dosing,” Stone added. “Further studies are needed to address these questions.”

https://www.newsweek.com/ketamine-shows-promise-treatment-adolescents-depression-1054021

A Lack of This One Molecule Might Be The Reason Millions of People Have Depression

By Michelle Star

People who live with depression have low blood levels of a specific molecule, new medical research has revealed. It’s called acetyl-L-carnitine, and those with particularly severe, treatment-resistant or childhood onset depression were found to have the lowest levels.

Naturally produced by the body, acetyl-L-carnitine plays a crucial role in metabolising fat and the production of energy. It’s also widely available as a dietary supplement – not some strange and esoteric thing.

Now researchers from multiple institutions have found a link to depression, noticing a clear correlation between the condition and noticeably low levels of acetyl-L-carnitine.

In recent years, more and more evidence has been building to suggest this link. Since at least 1991, medical researchers have been aware of acetyl-L-carnitine’s potential to treat depression, particularly in geriatric and comorbid patients, with the substance showing greater efficacy than a placebo.

More recently, Carla Nasca of the Rockefeller University led a study on rodents, which found that acetyl-L-carnitine had a fast-acting antidepressant effect on rats, kicking into effect in just a few days, rather than the weeks it takes for drugs like SSRIs.

Now Nasca and colleagues have conducted a study on human patients to see if there’s a basis for a similar trial in people.

“As a clinical psychiatrist, I have treated many people with this disorder in my practice,” said Stanford University School of Medicine psychiatrist Natalie Rasgon.

“It’s the number one reason for absenteeism at work, and one of the leading causes of suicide. Worse, current pharmacological treatments are effective for only about 50 percent of the people for whom they’re prescribed. And they have numerous side effects, often decreasing long term compliance.”

The research team recruited 71 patients with a diagnosis of depression. These were men and women, aged between 20 and 70. They also recruited 45 demographically matched healthy controls.

The patients had to fill out a detailed questionnaire, undergo a clinical assessment and medical history, and give a blood sample. Of the patients with depression, 28 had moderate depression and 43 had severe depression at the time of the study.

When compared to the age- and sex-matched healthy controls, the patients with depression had substantially lower levels of acetyl-L-carnitine.

Those with the most severe depression had the lowest levels. This included patients whose depression had resisted antidepressant drugs, those with early onset, and those who had experienced childhood abuse, neglect, poverty or violence.

These patients constitute around 25-30 percent of all people suffering depression, and are the most in need of help, the researchers said.

But there are a few steps to be done before acetyl-L-carnitine supplements can be approved as a treatment. In particular, clinical trials on human patients with depression, since, as we know, results from rodent models can’t always be replicated in humans.

The researchers also don’t know the reason for the correlation, or the effect it has. The rat research suggests that acetyl-L-carnitine plays a role in the brain, preventing the excessive firing of excitatory neurons, but this will need to be explored further as well.

“We’ve identified an important new biomarker of major depression disorder,” Rasgon said.

“We didn’t test whether supplementing with that substance could actually improve patients’ symptoms. What’s the appropriate dose, frequency, duration? We need to answer many questions before proceeding with recommendations, yet. This is the first step toward developing that knowledge, which will require large-scale, carefully controlled clinical trials.”

https://www.sciencealert.com/depression-linked-to-low-blood-levels-of-acetyl-l-carnitine-human-study