Posts tagged animal model
Articles and news from the latest research reports.
(Image caption: Researchers at Cold Spring Harbor Laboratory have identified the neurons in the brain that determine if a mouse will learn to cope with stress or become depressed. These neurons, located in a region of the brain known as the medial prefrontal cortex (green, left image), become hyperactive in depressed mice (right panel is close-up of left, yellow indicates activation). The team showed that this enhanced activity in fact causes depression.)
Dealing with stress – to cope or to quit?
We all deal with stress differently. For many of us, stress is a great motivator, spurring a renewed sense of vigor to solve life’s problems. But for others, stress triggers depression. We become overwhelmed, paralyzed by hopelessness and defeat. Up to 20% of us will struggle with depression at some point in life, and researchers are actively working to understand how and why this debilitating mental disease develops.
Today, a team of researchers at Cold Spring Harbor Laboratory (CSHL) led by Associate Professor Bo Li reveals a major insight into the neuronal basis of depression. They have identified the group of neurons in the brain that determines how a mouse responds to stress — whether with resilience or defeat.
For years, scientists have relied on brain imaging to look for neuronal changes during depression. They found that a region of the brain known as the medial prefrontal cortex (mPFC) becomes hyperactive in depressed people. This area of the brain is well known to play a role in the control of emotions and behavior, linking our feelings with our actions. But brain scans aren’t able to determine if increased activity in the mPFC causes depression, or if it is simply a byproduct of other neuronal changes.
Dr. Li set out to identify the neuronal changes that underlie depression. In work published today in The Journal of Neuroscience,Li and his team, including Minghui Wang, Ph.D. and Zinaida Perova, Ph.D., used a mouse model for depression, known as “learned helplessness.” They combined this with a genetic trick to mark specific neurons that respond to stress. They discovered that neurons in the mPFC become highly excited in mice that are depressed. These same neurons are weakened in mice that aren’t deterred by stress – what scientists call resilient mice.
But the team still couldn’t be sure that enhanced signaling in the mPFC actually caused depression. To test this, they engineered mice to mimic the neuronal conditions they found in depressed mice. “We artificially enhanced the activity of these neurons using a powerful method known as chemical genetics,” says Li. “The results were remarkable: once-strong and resilient mice became helpless, showing all of the classic signs of depression.”
These results help explain how one promising new treatment for depression works and may lead to improvements in the treatment.
Doctors have had some success with deep brain stimulation (DBS), which suppresses the activity of neurons in a very specific portion of the brain. “We hope that our work will make DBS even more targeted and powerful,” says Li, “and we are working to develop additional strategies based upon the activity of the mPFC to treat depression.”
Next, Li is looking forward to exploring how the neurons in the mPFC become hyperactive in helpless mice. “These active neurons are surrounded by inhibitory neurons,” says Li. “Are the inhibitory neurons failing? Or are the active neurons somehow able to bypass their controls? These are some of the many open questions we are pursuing to understand the how depression develops.”
Stem Cell Therapy Shows Promise for MS in Mouse Model
Mice crippled by an autoimmune disease similar to multiple sclerosis (MS) regained the ability to walk and run after a team of researchers led by scientists at The Scripps Research Institute (TSRI), University of Utah and University of California (UC), Irvine implanted human stem cells into their injured spinal cords.
Remarkably, the mice recovered even after their bodies rejected the human stem cells. “When we implanted the human cells into mice that were paralyzed, they got up and started walking a couple of weeks later, and they completely recovered over the next several months,” said study co-leader Jeanne Loring, a professor of developmental neurobiology at TSRI.
Thomas Lane, an immunologist at the University of Utah who co-led the study with Loring, said he had never seen anything like it. “We’ve been studying mouse stem cells for a long time, but we never saw the clinical improvement that occurred with the human cells that Dr. Loring’s lab provided,” said Lane, who began the study at UC Irvine.
The mice’s dramatic recovery, which is reported online ahead of print by the journal Stem Cell Reports, could lead to new ways to treat multiple sclerosis in humans.
"This is a great step forward in the development of new therapies for stopping disease progression and promoting repair for MS patients,” said co-author Craig Walsh, a UC Irvine immunologist.
Stem Cell Therapy for MS
MS is an autoimmune disease of the brain and spinal cord that affects more than a half-million people in North America and Europe, and more than two million worldwide. In MS, immune cells known as T cells invade the upper spinal cord and brain, causing inflammation and ultimately the loss of an insulating coating on nerve fibers called myelin. Affected nerve fibers lose their ability to transmit electrical signals efficiently, and this can eventually lead to symptoms such as limb weakness, numbness and tingling, fatigue, vision problems, slurred speech, memory difficulties and depression.
Current therapies, such as interferon beta, aim to suppress the immune attack that strips the myelin from nerve fibers. But they are only partially effective and often have significant adverse side effects. Loring’s group at TSRI has been searching for another way to treat MS using human pluripotent stem cells, which are cells that have the potential to transform into any of the cell types in the body.
Loring’s group has been focused on turning human stem cells into neural precursor cells, which are an intermediate cell type that can eventually develop into neurons and other kinds of cells in the nervous system. In collaboration with Lane’s group, Loring’s team has been testing the effects of implanting human neural precursor cells into the spinal cords of mice that have been infected with a virus that induces symptoms of MS.
A Domino Effect
The transformation that took place in the largely immobilized mice after the human neural precursor cells were injected into the animals’ damaged spinal cords was dramatic. “Tom called me up and said, ‘You’re not going to believe this,’” Loring said. “He sent me a video, and it showed the mice running around the cages. I said, ‘Are you sure these are the same mice?’”
Even more remarkable, the animals continued walking even after the human cells were rejected, which occurred about a week after implantation. This suggests that the human stem cells were secreting a protein or proteins that had a long-lasting effect on preventing or impeding the progression of MS in the mice, said Ron Coleman, a TSRI graduate student in Loring’s lab who was first author of the paper with Lu Chen of UC Irvine. “Once the human stem cells kick that first domino, the cells can be removed and the process will go on because they’ve initiated a cascade of events,” said Coleman.
The scientists showed in the new study that the implanted human stem cells triggered the creation of white blood cells known as regulatory T cells, which are responsible for shutting down the autoimmune response at the end of an inflammation. In addition, the implanted cells released proteins that signaled cells to re-myelinate the nerve cells that had been stripped of their protective sheaths.
A Happy Accident
The particular line of human neural precursor cells used to heal the mice was the result of a lucky break. Coleman was using a common technique for coaxing human stem cells into neural precursor cells, but decided partway through the process to deviate from the standard protocol. In particular, he transferred the developing cells to another Petri dish.
“I wanted the cells to all have similar properties, and they looked really different when I didn’t transfer them,” said Coleman, who was motivated to study MS after his mother died from the disease. This step, called “passaging,” proved key. “It turns out that passaging alters the types of proteins that the cells express,” he said.
Loring called the creation of the successful neural precursor cell line a “happy accident.” “If we had used common techniques to create the cells, they wouldn’t have worked,” she said. “We’ve shown that now. There are a dozen different ways to make neural precursor cells, and only this one has worked so far. We now know that it is incredibly important to make the cells the same way every time.”
Hot On the Trail
The team is now working to discover the particular proteins that its unique line of human precursor cells release. One promising candidate is a class of proteins known as transforming growth factor beta, or TGF-B, which other studies have shown is involved the creation of regulatory T cells. Experiments by the scientists showed that the human neural precursor cells released TGF-B proteins while they were inside the spinal cords of the impaired mice. However, it’s also likely that other, as yet unidentified, protein factors may also be involved in the mice’s healing.
If the team can pinpoint which proteins released by the neural precursor cells are responsible for the animals’ recovery, it may be possible to devise MS treatments that don’t involve the use of human stem cells. “Once we identify the factors that are responsible for healing, we could make a drug out of them,” said Lane. Another possibility, Loring said, might be to infuse the spinal cords of humans affected by MS with the protein factors that promote healing.
A better understanding of what makes these human neural precursor cells effective in mice will be key to developing either of these therapies for humans. “We’re on the trail now of what these cells do and how they work,” Loring said.
(Source: scripps.edu)
Scientists slow brain tumor growth in mice
Much like using dimmer switches to brighten or darken rooms, biochemists have identified a protein that can be used to slow down or speed up the growth of brain tumors in mice.
Brain and other nervous system cancers are expected to claim 14,320 lives in the United States this year.
The results of the preclinical study led by Eric J. Wagner, Ph.D., and Ann-Bin Shyu, Ph.D., of The University of Texas Health Science Center at Houston (UTHealth) and Wei Li, Ph.D., of Baylor College of Medicine appear in the Advance Online Publication of the journal Nature.
“Our work could lead to the development of a novel therapeutic target that might slow down tumor progression,” said Wagner, assistant professor in the Department of Biochemistry and Molecular Biology at the UTHealth Medical School.
Shyu, professor and holder of the Jesse H. Jones Chair in Molecular Biology at the UTHealth Medical School, added, “This link to brain tumors wasn’t previously known.”
“Its role in brain tumor progression was first found through big data computational analysis, then followed by animal-based testing. This is an unusual model for biomedical research, but is certainly more powerful, and may lead to the discovery of more drug targets,” said Li, an associate professor in the Dan L. Duncan Cancer Center and Department of Molecular and Cellular Biology at Baylor.
Wagner, Shyu, Li and their colleagues discovered a way to slow tumor growth in a mouse model of brain cancer by altering the process by which genes are converted into proteins.
Appropriately called messenger RNA for short, these molecules take the information inside genes and use it to make body tissues. While it was known that the messenger RNA molecules associated with the cancerous cells were shorter than those with healthy cells, the mechanism by which this occurred was not understood.
The research team discovered that a protein called CFIm25 is critical to keeping messenger RNA long in healthy cells and that its reduction promotes tumor growth. The key research finding in this study was that restoring CFIm25 levels in brain tumors dramatically reduced their growth.
“Understanding how messenger RNA length is regulated will allow researchers to begin to develop new strategies aimed at interfering with the process that causes unusual messenger RNA shortening during the formation of tumors,” Wagner said.
Additional preclinical tests are needed before the strategy can be evaluated in humans.
“The work described in the Nature paper by Drs. Wagner and Shyu stems from a high-risk/high-impact Cancer Prevention & Research Institute of Texas (CPRIT) proposal they submitted together and received several years ago,” said Rod Kellems, Ph.D., professor and chairman of the Department of Biochemistry and Molecular Biology at the UTHealth Medical School.
“Their research is of fundamental biological importance in that it seeks to understand the role of messenger RNA length regulation in gene expression,” Kellems said. “Using a sophisticated combination of biochemistry, genetics and bioinformatics, their research uncovered an important role for a specific protein that is linked to glioblastoma tumor suppression.”
(Source: uth.edu)
Elevating Brain Fluid Pressure Could Prevent Vision Loss
Scientists have found that pressure from the fluid surrounding the brain plays a role in maintaining proper eye function, opening a new direction for treating glaucoma — the second leading cause of blindness worldwide. The research is being presented at the 2014 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) this week in Orlando, Fla. (Abstract Title: Effect of translaminar pressure modification on the rat optic nerve head).
Using a rat model, researchers found that elevating the pressure of the fluid surrounding the brain can counterbalance elevated pressure in the eye, preventing the optic nerve from bending backward. Rats with higher fluid pressure from the brain maintained their ability to respond to light better than rats with lower pressure.
The brain and eye are connected by the optic nerve. In diseases like glaucoma — where vision loss is associated with elevated pressure within the eye — the optic nerve bows backward, away from the eye and toward the brain. This investigation might explain why some people with normal eye pressure develop glaucoma, and why people with intraocular pressure never develop the condition.
(Source: newswise.com)
Sleep Researchers at SRI International Identify Promising New Treatment for Narcolepsy
Neuroscientists at SRI International have found that a form of baclofen, a drug used to treat muscle spasticity, works better at treating narcolepsy than the best drug currently available when tested in mice.
According to the National Institute of Neurological Disorders and Stroke (NINDS), narcolepsy, a chronic neurologic disorder characterized by excessive daytime sleepiness, is not a rare condition, but is under-recognized and under-diagnosed. It is estimated to impact 1 in 2,000 people worldwide.
In back-to-back papers published in the May 7 issue of The Journal of Neuroscience, Thomas Kilduff, Ph.D., who directs the Center for Neuroscience within SRI Biosciences, Sarah Wurts Black, Ph.D., a research scientist in the Center for Neuroscience, and colleagues present a mouse model of narcolepsy that mimics the human disorder better than other models currently in use. Kilduff, Black and the SRI team then used the new narcolepsy model alongside a standard model to investigate a novel therapeutic pathway and to identify a promising way of treating narcolepsy.
"Our work is an example of how basic research can lead to a potential new therapy for a disease," said Kilduff. His team found that a form of baclofen, R-baclofen, works in both mouse models much better than the leading FDA-approved therapeutic for narcolepsy. (Baclofen, which has been available for more than 50 years, is a chemical compound that exists as a mixture of two isomers, designated R and S.) "The next step would be to perform a study in narcoleptic patients to determine its potential for treatment of human narcolepsy."
In humans, narcolepsy onset is typically during adolescence or later, but diagnosis may take more than a decade, making it difficult to study the progression of the disease. The lack of definitive mechanisms to explain what goes awry in the brain’s ability to regulate sleep-wake cycles has consequently yielded drugs that only address the symptoms, rather than the underlying causes, of narcolepsy.
In the first of the two papers, “Conditional Ablation of Orexin/Hypocretin Neurons: A New Mouse Model for the Study of Narcolepsy and Orexin System Function,” Kilduff and Black teamed with colleagues at five institutions in Japan to generate a model of narcolepsy that better mimics the human disorder. The existing model, called “Ataxin mice,” has been available for over 10 years. Although Ataxin mice have enabled researchers to study narcolepsy, an important limitation is that these mice are born with the deficiency of the neurotransmitter hypocretin that has been implicated in causing narcolepsy, whereas the onset of human narcolepsy typically occurs after puberty.
"The mouse model developed by Dr. Kilduff and his colleagues offers a new approach to study narcolepsy and to explore potential therapies for this devastating sleep disorder. This new model allows more precise control of the timing and extent of hypocretin/orexin neuron loss, and thus may better mimic human narcolepsy," said Janet He, Ph.D., program director at the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health.
In collaboration with Professor Akihiro Yamanaka of Nagoya University in Japan, formerly an SRI International Fellow in Dr. Kilduff’s laboratory, the research team genetically engineered a mouse in which the hypocretin neurons could be selectively eliminated at any age simply by removal of an antibiotic in the mouse food. In the new “DTA” model, degeneration of hypocretin neurons can be initiated after puberty, causing the mice to exhibit the two major symptoms of narcolepsy: excessive daytime sleepiness and cataplexy, the brief loss of muscle tone experienced by most narcoleptics.
In the second paper, “GABAB Agonism Promotes Sleep and Reduces Cataplexy in Murine Narcolepsy,” Black, Kilduff and colleagues used the new DTA model and the Ataxin model to compare R-baclofen against gamma-hydroxybutyrate (GHB). Sodium oxybate, the sodium salt of GHB, was approved by the FDA in 2002 as the only therapeutic for narcolepsy that simultaneously alleviates cataplexy, excessive daytime sleepiness and nocturnal sleep disruption. However, it remains unclear how this drug exerts its beneficial effects.
It was suspected that GHB works by affecting brain cells that respond to a neurotransmitter known as gamma-aminobutyric acid (GABA), which primarily functions to inhibit excitability and regulate muscle tone. To study the mechanism of action of GHB, SRI Biosciences’ researchers tested R-baclofen, which blocks the GABA receptors suspected to be the target of GHB.
The research team found that R-baclofen promoted sleep time and longer bouts of wakefulness during the appropriate times for mice and also suppressed cataplexy. GHB modestly reduced cataplexy and increased sleep intensity, but did not improve other symptoms of narcolepsy to the extent that R-baclofen did. “The improvement in wakefulness that we observed after R-baclofen was a particularly unexpected and important finding,” said Black.
"R-Baclofen works better than GHB in these two mouse models, but it remains to be determined whether it will work better in humans," cautioned Kilduff. "Although baclofen is already known to be safe for use in humans, the dose that is effective for spasticity may be different than the dose of R-baclofen that has the potential to treat narcolepsy."
Model Sheds New Light on Sports-related Brain Injuries
A new study has provided insight into the behavioral damage caused by repeated blows to the head. The research provides a foundation for scientists to better understand and potentially develop new ways to detect and prevent the repetitive sports injuries that can lead to the condition known as chronic traumatic encephalopathy (CTE).
The research – which appears online this week in the Journal of Neurotrauma – shows that mice with mild, repetitive traumatic brain injury (TBI) develop many of the same behavioral problems, such as difficultly sleeping, memory problems, depression, judgment and risk-taking issues, that have been associated with the condition in humans.
One of the barriers to potential treatments for TBI and CTE is that no model of the disease exists. Animal equivalents of human diseases are a critical early-stage tool in the scientific process of understanding a condition, developing new ways to diagnose it, and evaluating experimental therapies.
“This new model captures both the clinical aspects of repetitive mild TBI and CTE,” said Anthony L. Petraglia, M.D., a neurosurgeon with the University of Rochester School of Medicine and Dentistry and lead author of the study. “While public awareness of the long-term health risk of blows to the head is growing rapidly, our ability to scientifically study the fundamental neurological impact of mild brain injuries has lagged.”
There has been a great deal of discussion in recent years regarding concussions as a result of blows to the head in sports. An estimated 3.8 million sports-related concussions occur every year. Mild traumatic brain injury is also becoming more common in military personnel deployed in combat zones. Over time, the frequency and degree of these injuries can lead short and long-term neurological impairment and, in extreme examples, to CTE, a form of degenerative brain disease.
The experiments described in the study were designed in a manner that simulates the type of mild TBI that may occur in sports or other blows to the head. The researchers evaluated the mice’s performance in a series of tasks designed to measure behavior. These included tests to measure spatial and learning memory, anxiety and risk-taking behavior, the presence of depression-like behavior, sleep disturbances, and the electrical activity of their brain. The mice with repetitive mild TBI did poorly in every test and this poor performance persisted over time.
“These results resemble the spectrum of neuro-behavioral problems that have been reported and observed in individuals who have sustained multiple mild TBI and those who were subsequently diagnosed with CTE, including behaviors such as poor judgment, risk taking, and depression,” said Petraglia.
Petraglia and his colleagues also used the model to examine the damage that was occurring in the brains of the mice over time. The results, which will be published in a forthcoming paper, provide insight on the interaction between the brains repair mechanisms – in the forms of astrocytes and microglia – and the protein tau, which can have a toxic effect when triggered by mild traumatic brain injury.
“Undoubtedly further work is needed,” said Petraglia. “However, this study serves as a good starting point and it is hoped that with continued investigation this novel model will allow for a controlled, mechanistic analysis of repetitive mild TBI and CTE in the future, because it is the first to encapsulate the spectrum of this human phenomenon.”
(Source: urmc.rochester.edu)
Fruitfly Study Identifies Brain Circuit that Drives Daily Cycles of Rest, Activity
Amita Sehgal, PhD, a professor of Neuroscience at the Perelman School of Medicine, University of Pennsylvania, describes in Cell a circuit in the brain of fruit flies that controls their daily, rhythmic behavior of rest and activity. The new study also found that the fly version of the human brain protein known as corticotrophin releasing factor (CRF) is a major coordinating molecule in this circuit. Fly CRF, called DH44, is required for rest/activity cycles and is produced in cells that receive input from the clock cells in the fly brain. In mammals, CRF is secreted rhythmically and it drives the expression of glucocorticoids such as cortisol and is associated with stress and anxiety.
Animal models like flies are helping to fill gaps in current knowledge about how the brain works, notes Sehgal. Indeed, she says, the Brain Research through Advancing Innovative Neurotechnologies (BRAIN), initiative, a project of the National Institutes of Health, includes the study of simple animal models, which are expected to provide more detailed insight into brain function.
Though much is known about the cellular and molecular components of the clock, the connections that link clock cells to overt behaviors, such as rest/activity behavior, have not been identified. “This study is essentially a map-of-the-circuitry experiment,” says Sehgal, who is also an investigator with the Howard Hughes Medical Institute (HHMI). Like humans, flies are active during the day — walking, flying, feeding and mating — and spend most of the night asleep.
“We conducted a screen for circadian-relevant neurons in the flybrain and found that cells of the pars intercerebralis — the fly version of the mammalian hypothalamus — comprise an important component of the circadian output pathway for rest/activity rhythms in flies,” Sehgal says. The mammalian hypothalamus is a neuroendocrine structure that regulates sleep, circadian rhythms, feeding and, metabolism.
The Penn team did a random targeting of cells, activating neuronal firing with a transgene designed for this purpose, to see which cells are important in the rest/active behavior. They found that cells in the pars intercerebralis (PI) are essential for rhythmic behavior, and PI cells are connected to the clock cells through a circuit of at least two synapses.
Molecular profiling of PI cells identified the fly version of DH44 as a circadian molecule that is specifically expressed by PI neurons and required for normal rest/activity rhythms in flies. And, when the scientists selectively activated or removed just six PI cells positive for DH44, the fly’s activity cycles became irregular. In other words, the flies no longer restricted their sleep to the dark and their activity to the light, but instead showed more random distribution of these behaviors
New mouse model could revolutionize research in Alzheimer’s disease
In a study published today in Nature Neuroscience, a group of researchers led by Takaomi Saido of the RIKEN Brain Science Institute in Japan have reported the creation of two new mouse models of Alzheimer’s disease that may potentially revolutionize research into this disease.
Alzheimer’s disease, the primary cause of dementia in the elderly, imposes a tremendous social and economic burden on modern society. In Japan, the burden of the disease in 2050 is estimated to be a half a trillion US dollars, a figure equivalent to the government’s annual revenues.
Unfortunately, it has proven very difficult to develop drugs capable of ameliorating the disease. After a tremendous burst of progress in the 1990s, the pace of discoveries has slowed. Dr. Saido believes that part of the difficulty is the inadequacy of current mouse models to replicate the real conditions of Alzheimer’s disease and allow an understanding of the underlying mechanisms that lead to neurodegeneration. In fact, much of the research in Alzheimer’s disease over the past decade may be flawed, as it was based on unrealistic models.
The problem with older mouse models is that they overexpress a protein called amyloid precursor protein, or APP, which gives rise to the amyloid-beta (Abeta) peptides that accumulate in the brain, eventually leading to the neurodegeneration that characterizes Alzheimer’s disease. However, in mice the overexpression of APP gives rise to effects which are not seen in human Alzheimer’s disease.
For example, the APP mutant mice often die of unknown causes at a young age, and the group believes this may be related to the generation of toxic fragments of APP, such as CTF-beta. In addition, some of the fragments of APP could be neuroprotective, making it difficult to judge whether drugs are being effective due to their effect on Abeta peptides, which are known to be involved in human AD, or whether it is due to other effects that would not be seen in human disease. In addition, the gene for expressing APP is inserted in different places in the genome, and may knock out other genes, creating artifacts that are not seen in humans.
With this awareness, more than a decade ago Dr. Saido launched a project to develop a new mouse model that would allow more accurate evaluation of therapies for the disease. One of the major hurdles involved a part of the gene, intron 16, which they discovered was necessary for creating more specific models.
The first mice model they developed (NL-F/NL-F) was knocked in with two mutations found in human familial Alzheimer’s disease. The mice showed early accumulation of Abeta peptides, and importantly, were found to undergo cognitive dysfunction similar to the progression of AD seen in human patients. A second model, with the addition of a further mutation that had been discovered in a family in Sweden, showed even faster initiation of memory loss.
These new models could help in two major areas. The first model, which expresses high levels of the Abeta peptides, seems to realistically model the human form of AD, and could be used for elucidating the mechanism of Abeta deposition. The second model, which demonstrates AD pathology very early on, could be used to examine factors downstream of Abeta-40 and Abeta-42 deposition, such as tauopathy, which are believed to be involved in the neurodegeneration. These results may eventually contribute to drug development and to the discovery of new biomarkers for Alzheimer’s disease. The group is currently looking at several proteins, using the new models, which have potential to be biomarkers.
According to Dr. Saido, “We have a social responsibility to make Alzheimer’s disease preventable and curable. The generation of appropriate mouse models will be a major breakthrough for understanding the mechanism of the disease, which will lead to the establishment of presymptomatic diagnosis, prevention and treatment of the disease.”
Protein researchers closing in on the mystery of schizophrenia
Seven per cent of the adult population suffer from schizophrenia, and although scientists have tried for centuries to understand the disease, they still do not know what causes the disease or which physiological changes it causes in the body. Doctors cannot make the diagnosis by looking for specific physiological changes in the patient’s blood or tissue, but have to diagnose from behavioral symptoms.
In an attempt to find the physiological signature of schizophrenia, researchers from the University of Southern Denmark have conducted tests on rats, and they now believe that the signature lies in some specific, measurable proteins. Knowing these proteins and comparing their behaviour to proteins in the brains of not-schizophrenic people may make it possible to develop more effective drugs.
It is extremely difficult to study brain activity in schizophrenic people, which is why researchers often use animal models in their strive to understand the mysteries of the schizophrenic brain. Rat brains resemble human brains in so many ways that studying them makes sense if one wants to learn more about the human brain.
Schizophrenic symptoms in rats
The strong hallucinogenic drug phenocyclidine (PCP), also known as “angel’s dust”, provides a range of symptoms in people which are very similar to schizophrenia.
“When we give PCP to rats, the rats become valuable study objects for schizophrenia researchers,” explains Ole Nørregaard Jensen, professor and head of the Department of Biochemistry and Molecular Biology.
Along with Pawel Palmowski, Adelina Rogowska-Wrzesinska and others, he is the author of a scientific paper about the discovery, published in the international Journal of Proteome Research.
Among the symptoms and reactions that can be observed in both humans and rats are changes in movement and reduced cognitive functions such as impaired memory, attention and learning ability.
"Scientists have studied PCP rats for decades, but until now no one really knew what was going on in the rat brains at the molecular level. We now present what we believe to be the largest proteomics data set to date," says Ole Nørregaard Jensen.
PCP is absorbed very quickly by the brain, and it only stays in the brain for a few hours. Therefore, it was important for researchers to examine the rats’ brain cells soon after the rats were injected with the hallucinogenic drug.
"We could see changes in the proteins in the brain already after 15 minutes. And after 240 minutes, it was almost over," says Ole Nørregaard Jensen.
The University of Southern Denmark holds some of the world’s most advanced equipment for studying proteins, and Ole Nørregaard Jensen and his colleagues used the university’s so-called mass spectrometres for their protein studies.
352 proteins cause brain changes
"We found 2604 proteins, and in 352 of them, we saw changes that can be associated with the PCP injections. These 352 proteins will be extremely interesting to study in closer detail to see if they also alter in people with schizophrenia - and if that’s the case, it will of course be interesting to try to develop a drug that can prevent the protein changes that lead to schizophrenia," says Ole Nørregaard Jensen about the discovery and the work that now lies ahead.
The 352 proteins in rat brains responded immediately when the animals were exposed to PCP. Roughly speaking, the drug made proteins turn on or off when they should not turn on and off. This started a chain reaction of other disturbances in the molecular network around the proteins, such as changes in metabolism and calcium balance.
"These 352 proteins are what causes the rats to change their behaviour - and the events are probably comparable to the devastating changes in a schizophrenic brain," explains Ole Nørregaard Jensen.
The protocol for studying rat brain proteins with mass spectrometry, developed by Ole Nørregaard Jensen and his colleagues, is not limited to schizophrenia studies - it can also be used to explore other diseases.
The research was a collaboration between the University of Southern Denmark, the Danish Technological Institute and NeuroSearch A/S.
Details about the experiment
Twelve rats were used for the experiment. Six received an injection with the hallucinogenic drug PCP (10 mg/kg body weight), and six were injected with a saline solution to serve as controls. After 15 minutes, the first two animals in each group were killed and within less than two minutes, samples of their brains (temporal lobes) were taken and quickly frozen in liquid nitrogen.
After 30 and 240 minutes, respectively, the same was done to other rats. All experiments were conducted in accordance with Danish and EU guides for the handling of laboratory animals. The collected tissue samples were then subjected to various mass spectrometric protein analyses. The analyses revealed differences in the phosphorylation of proteins indicating which proteins had been affected by the drug PCP.
Interpretation of the complex protein data set suggest that PCP affects a number of processes in brain cells and leads to changes in calcium balance in the brain cells, changes in the transport of substances into and out of cells, changes in cell metabolism and changes in the structure of the cell’s internal skeleton, the cytoskeleton.
Dog watch - How attention changes in the course of a dog’s life
Dogs are known to be Man’s best friend. No other pet has adjusted to Man’s lifestyle as this four-legged animal. Scientists at the Messerli Research Institute at the Vetmeduni Vienna, have been the first to investigate the evolution of dogs’ attentiveness in the course of their lives and to what extent they resemble Man in this regard. The outcome: dogs’ attentional and sensorimotor control developmental trajectories are very similar to those found in humans. The results were published in the journal Frontiers in Psychology.
Dogs are individual personalities, possess awareness, and are particularly known for their learning capabilities, or trainability. To learn successfully, they must display a sufficient quantity of attention and concentration. However, the attentiveness of dogs’ changes in the course of their lives, as it does in humans. The lead author Lisa Wallis and her colleagues investigated 145 Border Collies aged 6 months to 14 years in the Clever Dog Lab at the Vetmeduni Vienna and determined, for the first time, how attentiveness changes in the entire course of a dog’s life using a cross-sectional study design.
Humans are more interesting for dogs than objects
To determine how rapidly dogs of various age groups pay attention to objects or humans, the scientists performed two tests. In the first situation the dogs were confronted with a child’s toy suspended suddenly from the ceiling. The scientists measured how rapidly each dog reacted to this occurrence and how quickly the dogs became accustomed to it. Initially all dogs reacted with similar speed to the stimulus, but older dogs lost interest in the toy more rapidly than younger ones did.
In the second test situation, a person known to the dog entered the room and pretended to paint the wall. All dogs reacted by watching the person and the paint roller in the person’s hands for a longer duration than the toy hanging from the ceiling.
Wallis’ conclusion: “So-called social attentiveness was more pronounced in all dogs than “non-social” attentiveness. The dogs generally tended to react by watching the person with the object for longer than an object on its own. We found that older dogs - like older human beings - demonstrated a certain calmness. They were less affected by new items in the environment and thus showed less interest than younger dogs.”
Selective attention is highest in mid-adulthood
In a further test the scientists investigated so-called selective attention. The dogs participated in an alternating attention task, where they had to perform two tasks consecutively. First, they needed to find a food reward thrown onto the floor by the experimenter, then after eating the food, the experimenter waited for the dog to establish eye contact with her. These tasks were repeated for a further twenty trials. The establishment of eye contact was marked by a clicking sound produced by a “clicker” and small pieces of hot dog were used as a reward. The time spans to find the food and look up into the face were measured. With respect to both time spans, middle-aged dogs (3 to 6 years) reacted most rapidly.
Under these test conditions, sensorimotor abilities were highest among dogs of middle age. Younger dogs fared more poorly probably because of their general lack of experience. Motor abilities in dogs as in humans deteriorate with age. Humans between the age of 20 and 39 years experience a similar peak in sensorimotor abilities,” says Wallis.
Adolescent dogs have the steepest learning curve
Dogs also go through a difficult phase during adolescence (1-2 years) which affects their ability to pay attention. This phase of hormonal change may be compared to puberty in Man. Therefore, young dogs occasionally reacted with some delay to the clicker test. However, Wallis found that adolescent dogs improved their performance more rapidly than other age groups after several repetitions of the clicker test. In other words, the learning curve was found to be steepest in puberty. “Thus, dogs in puberty have great potential for learning and therefore trainability” says Wallis.
Dogs as a model for ADHD and Alzheimer’s disease
As the development of attentiveness in the course of a dog’s life is similar to human development in many respects, dogs make appropriate animal models for various human psychological diseases. For instance, the course of diseases like ADHD (attention deficit/hyperactivity disorder) or Alzheimer’s can be studied by observing the behavior of dogs. In her current project Wallis is investigating the effects of diet on cognition in older dogs together with her colleague Durga Chapagain. The scientists are still looking for dog owners who would like to participate in a long-term study.