动物模型 z-bo 2020-11-30 370

　　In terms of cognitive ability research, researchers have made great progress using animal experiments. The next step is to establish a rodent model that can be used for drug development.

　　In 1997, Patricio O’ began to have his own laboratory at Donnell Albany Medical College. At that time, the research on schizophrenia seemed to have experienced a long lag and began to make some progress.

　　For decades, in the field of schizophrenia research, people have always believed that the cause of the disease is the increase in the concentration of dopamine in the brain, especially the concentration of dopamine in the striatum in the brain. The striatum is located in the cerebral cortex. A small area under. By the 1990s, it was discovered that the pathogenesis of dopamine was incomplete and could not fully explain the pathogenesis of schizophrenia. Through in-vivo imaging techniques, such as computer tomography (CT) and magnetic resonance imaging (MRI), as well as the analysis of research data after the death of schizophrenia patients, it has been shown that there are other cerebral cortex-related effects and such as valleys. Neurotransmitter system factors such as amino acid and serotonin are involved in pathogenicity. Biologists have also begun to construct models of the disease in transgenic mice to study the genetics and etiology of the disease.

　　These advances provide researchers with new perspectives and new methods for research through animal models. In the classic rodent model used in the study of schizophrenia, researchers will inject animals with amphetamines-a substance that can increase the concentration of dopamine at nerve synapses, causing people to produce hallucinations, delusions and other symptoms-and then correct Their behavior is monitored to observe whether there is excessive activity or passive avoidance behavior. As the research progressed, researchers began to use other drugs, such as phenxigram (PCP) and ketamine (K powder), both of which can interfere with the glutamate receptor NMDA. Researchers can also knock out specific genes, such as those responsible for encoding neurotransmitter receptors, to conduct related research.

　　O’Donnell is very interested in one of these methods, in which the hippocampus of the newborn animal’s brain needs to be chemically destroyed. After receiving this intervention, the newborn rodents behaved normally at first, but over time, they began to show social withdrawal and overreaction to stressors. Analysis of their brain tissue after death can reveal these problems. There have been some physiological changes in the cerebral cortex of animals. These results are consistent with the gradually accepted hypothesis: schizophrenia is a developmental disorder. "In my opinion, it is very amazing that although brain damage appears very early, abnormal behavior does not occur until adolescence," said O'Donnell, who is currently a neuroscience company at Pfizer. Head and Vice President of the Department of Psychiatry and Abnormal Behavior Group.

　　Since then, there have been more and more ways to simulate the symptoms or potential physiological effects of schizophrenia. With the advent of whole-genome sequencing, researchers can easily and accurately find disease-related genes so that they can be knocked out or interfered in mouse models. Some researchers have also set their sights on environmental stressors, such as fetal infections, social isolation in the early stages of growth, stress or trauma. Others give animals drugs such as amphetamines, ketamine, and PCP. Researchers have also begun to combine these measures-putting environmental pressure on mice that do not carry genes related to schizophrenia.

　　Although there have been so many new methods and methods, when it comes to drug research and development, we ask a question: What is the best model? "There are so many risk factors, so many variables-dopamine system, serotonin, GABA, you can just say one at will," Thomas Steckler said. He is a behavioral neuroscientist at Janssen Research and Development Company in Bells, Belgium, engaged in drug development. "It's just that we don't know what is the best model."

　　Break the barriers of similar drugs

　　Animal models have two functional components: First, manipulability: used to simulate the characteristics of diseases; second, detectability—detection of behavior patterns or other aspects—used to measure the effects of manipulation of the model change. Researchers in the field of schizophrenia have made great progress in mastering the latter, but for the former, they are still at an unclear stage.

　　For a long time, the research and development of drugs for schizophrenia has mainly focused on mental disorders and delusions, because these two types of drugs are currently the only two types of antipsychotic drugs on the market, and the new drugs developed can be easily compared with them. Of course, as expected, this strategy is not ideal. "If you just keep making things that already exist and compare them, how can there be any progress?" said Bita Moghaddam, a neuroscientist at the University of Pittsburgh. "In the past forty to fifty years, when everything we did was not enough, we kept producing'Me too' drugs."

　　In the last 15 years, more and more studies have shown that in addition to mental confusion, schizophrenia has other major symptoms that are equally important: difficulty with working memory, difficulty concentrating, and other cognitive disorders. Drug research and development strategies have also changed, and the construction of many animal models has become more straightforward. "It is very difficult to simulate mental confusion or negative symptoms-such as apathy, lack of motivation, etc.-but we still know a lot about cognitive abilities and the brain system, and how it compares to the human brain," Cambridge University Said Trevor Robbins, a cognitive neuroscientist at.

　　Some researchers, including his laboratory, have constructed a set of methods to conduct behavioral testing on the cognitive process of animals, which can match the cognitive testing of patients with schizophrenia. For example, one of the experiments is to set up five sites in the cage where the mice are located. Short stimuli can be performed at these five sites. The researcher detects the accuracy of the mice’s response to the stimuli, and also Observe how the mice restrain their impulse response before the stimulus occurs. The two main collaborative projects aim at drug development for cognitive impairment, and are currently committed to verifying these tasks so that researchers can determine whether their methods and research directions are correct. In the United States, researchers are participating in a project called "Cognitive Neuroscience Therapy Research for Improving the Cognitive Ability of Patients with Schizophrenia (CNTRICS)", funded by the National Institute of Mental Health. Recently, researchers have just reached an agreement on a research project that best reflects the six different cognitive and behavioral disorders, including working memory, executive ability, and behavioral motivation.

　　At the same time, as part of a cooperation project that has been in place for five years and invested 20 million euros (28 million US dollars) in Europe in 2009, eight companies including Janssen, Eli Lilly, Novartis, etc. Industry giants work together to establish a set of standard methods that can be used in preclinical trials of new drugs. The collaborative project is called NEWMEDS (Novel Methods leading to New Medications in Depression and Schizophrenia), and it has attracted more and more participants to conduct the same experiments to ensure the reliability of its methods. "We started with target recognition," said Mark Tricklebank, a behavioral neuroscientist at Eli Lilly and Company, currently responsible for the coordination of the animal model branch of the NEWMEDS project. "We found that everyone has some small differences in specific methods when conducting related experiments," he said. For example, the researchers used different sizes of experimental space, or the size of the experimental subjects were different, or they were monitored at different times of the day.

　　NEWMEDS spends several months in the standardization process of each test method to get the final version. The methods used by CNTRICS and NEWMEDS have a lot in common. However, since the goal of NEWMEDS is to be the standard method for testing in the pharmaceutical industry, it is more inclined to simple and convenient methods.

　　"We are currently at the stage where we can scientifically detect animal behaviors that can match human cognitive modules, at least we think so," Steckler said. However, it is much more difficult to construct the defects targeted by drug treatments in animal models, he said.

　　Causes and defects

　　O’Donnell said that with so many manipulative methods to choose from, researchers can construct many methods to verify various biological-based hypotheses. For example, a characteristic of schizophrenia is that the number of interneurons in the frontal cortex is greatly reduced, which is also present in many animal models. In order to prove whether this mechanism can be used as a targeted therapy to cure the symptoms of the disease, researchers need to test various research drugs on animal models. But so far, the method adopted by the pharmaceutical industry is still the traditional and old way, using drugs to induce the model to produce corresponding symptoms. Although pharmaceutical companies will also use results from animal model experiments, the use of bio-specific based models has not yet formed a climate, O’Donnell said.

　　It is really difficult, Steven Siegel pointed out that he is the head of the Translational Neuroscience Project at the University of Pennsylvania. He revealed that researchers from pharmaceutical companies have begun to contact his research team to discuss animal models with promising and reproducible applications. Some companies are already preparing to invest a lot of money in related cooperation.

　　On the other hand, the research and development personnel of pharmaceutical companies believe that the research results from academia cannot always be repeated. Steckler gave an example: A scientist discovered that mice that have knocked out the risk of schizophrenia also have cognitive deficits. "In academia, this result is not bothersome; because all you need is to publish these findings," Stecker said. However, in the pharmaceutical industry, it is completely different. What we need is repeatable and sufficiently strong data support, he said. And there is another problem: If there are no drugs that can improve the cognitive abilities of patients with schizophrenia, the testing of animal models cannot be carried out effectively.

　　In addition to projects in the field of cognitive ability, NEWMEDS also hopes to make breakthroughs in animal models. The organization is currently working to establish a standardized method for trauma operations, injecting MAM (methylazoxymethanol acetate) into pregnant mice or rats, which can block cell division during embryonic development. Due to hippocampal trauma, when animals grow up to adolescence, many typical features of schizophrenia will appear, such as thin cerebral cortex, ventricular enlargement, decreased number of interneurons in the frontal cortex, and changes in cognitive ability.

　　Although in the operation process, as far as possible to maintain the consistency of various variables, such as animal feeding, drug injection equipment and dosage, etc., the results obtained by different research groups are still different, and some animals even do not show the Some changes. When it was tested a year later, the problem came. "The difficulty lies in how to accurately determine which animals to use for drug treatment; only those animals that are indeed defective can be used in drug trials in order to obtain convincing results," Tricklebank said. The research team combined various methods, such as brain activation, and other physiological methods that can reflect whether the drug is effective.

　　Tricklebank said that even if the above problems are solved, there is still a big question: can the drug activity in animals be equal to the drug activity in humans? Of course, to succeed, you can only move forward step by step, solving problems one by one. Robbins, head of the animal model group of the NEWMEDS project, said, "In my opinion, we are just at the starting point of solving these problems."