Archive for the ‘dopamine’ Category

Everyone knows it’s easier to learn about a topic you’re curious about. Now, a new study reveals what’s going on in the brain during that process, revealing that such curiosity may give a person a memory boost.

When participants in the study were feeling curious, they were better at remembering information even about unrelated topics, and brain scans showed activity in areas linked to reward and memory.

The results, detailed October 2 in the journal Neuron, hint at ways to improve learning and memory in both healthy people and those with neurological disorders, the researchers said.

“Curiosity may put the brain in a state that allows it to learn and retain any kind of information, like a vortex that sucks in what you are motivated to learn, and also everything around it,” Matthias Gruber, a memory researcher at the University of California, Davis, said in a statement. “These findings suggest ways to enhance learning in the classroom and other settings.”

Gruber and his colleagues put people in a magnetic resonance imaging (MRI) scanner and showed them a series of trivia questions, asking them to rate their curiosity about the answers to those questions. Later, the participants were shown selected trivia questions, then a picture of a neutral face during a 14-second delay, followed by the answer. Afterward, the participants were given a surprise memory test of the faces, and then a memory test of the trivia answers.

Not surprisingly, the study researchers found that people remembered more information about the trivia when they were curious about the trivia answers. But unexpectedly, when the participants were curious, they were also better at remembering the faces, an entirely unrelated task. Participants who were curious were also more likley than others to remember both the trivia information and unrelated faces a day later, the researchers found.

The brain scans showed that, compared with when their curiosity wasn’t piqued, when people were curious, they showed more activation of brain circuits in the nucleus accumbens, an area involved in reward. These same circuits, mediated by the neurochemical messenger dopamine, are involved in forms of external motivation, such as food, sex or drug addiction.

Finally, being curious while learning seemed to produce a spike of activity in the hippocampus, an area involved in forming new memories, and strengthened the link between memory and reward brain circuits.

The study’s findings not only highlight the importance of curiosity for learning in healthy people, but could also give insight into neurological conditions. For example, as people age, their dopamine circuits tend to deteriorate, so understanding how curiosity affects these circuits could help scientists develop treatments for patients with memory disorders, the researchers said.

http://www.livescience.com/48121-curiosity-boosts-memory-learning.html

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A new study has found that activating natural resilience in the brain could reduce susceptibility for stress in mice, and potentially humans.

Depressive behaviors in mice are often linked to “out-of-balance” neuron activity in the brain’s reward circuit. Suppressing or stopping this hyperactive neuron activity was typically thought to treat this susceptibility to depression or anxiety — but the new study has found quite the opposite.

“To our surprise, neurons in this circuit harbor their own self-tuning, homeostatic mechanism of natural resilience,” Ming-Hu Han of the Icahn School of Medicine at Mount Sinai in New York City, explained in a press release. What this means is that instead of suppressing this excessive neuron activity, boosting it provided a self-stabilizing response, re-establishing balance and producing an antidepressant-like effect.

The mice that were once vulnerable to being anxious, listless, depressed or withdrawn after socially stressful experiences stopped exhibiting these behaviors after their neuron activity received a boost. “As we get to the bottom of a mystery that has perplexed the field for more than a decade, the story takes an unexpected twist that may hold clues to future antidepressants that would at through this counterintuitive resilience mechanism,” Dr. Thomas Insel, NIMH Director, said in the press release.

In susceptible mice, neurons that secrete dopamine — a feel-good hormone — from a reward circuit area called the ventral tegmental area (VTA) become unusually hyperactive. This hyperaction was much higher in mice that were resilient to stress, “even though they were spared the runaway dopamine activity and depression-related behaviors,” the press release reads. Using this logic, the susceptible mice just needed a boost in activation in these neurons to produce resilience.

What is interesting about this study is that it points to the power of the body and brain’s self-correcting prowess. “Homeostatic mechanisms finely regulate other critical components of physiology required for survival — blood glucose and oxygen, body temperature, blood pressure,” Lois Winsky, chief of the NIMH Molecular, Cellular, and Genomic Neuroscience Research Branch, said in the press release. “Similar mechanisms appear to also maintain excitatory balance in brain cells. This study shows how they may regulate circuits underlying behavior.”

http://www.medicaldaily.com/boosting-excess-neuron-activity-builds-resilience-mice-vulnerable-depression-277452

cocaine

Researchers at Weill Cornell Medical College have successfully tested their novel anti-cocaine vaccine in primates, bringing them closer to launching human clinical trials. Their study, published online by the journal Neuropsychopharmacology, used a radiological technique to demonstrate that the anti-cocaine vaccine prevented the drug from reaching the brain and producing a dopamine-induced high.

“The vaccine eats up the cocaine in the blood like a little Pac-man before it can reach the brain,” says the study’s lead investigator, Dr. Ronald G. Crystal, chairman of the Department of Genetic Medicine at Weill Cornell Medical College. “We believe this strategy is a win-win for those individuals, among the estimated 1.4 million cocaine users in the United States, who are committed to breaking their addiction to the drug,” he says. “Even if a person who receives the anti-cocaine vaccine falls off the wagon, cocaine will have no effect.”

Dr. Crystal says he expects to begin human testing of the anti-cocaine vaccine within a year.

Cocaine, a tiny molecule drug, works to produce feelings of pleasure because it blocks the recycling of dopamine — the so-called “pleasure” neurotransmitter — in two areas of the brain, the putamen in the forebrain and the caudate nucleus in the brain’s center. When dopamine accumulates at the nerve endings, “you get this massive flooding of dopamine and that is the feel good part of the cocaine high,” says Dr. Crystal.

The novel vaccine Dr. Crystal and his colleagues developed combines bits of the common cold virus with a particle that mimics the structure of cocaine. When the vaccine is injected into an animal, its body “sees” the cold virus and mounts an immune response against both the virus and the cocaine impersonator that is hooked to it. “The immune system learns to see cocaine as an intruder,” says Dr. Crystal. “Once immune cells are educated to regard cocaine as the enemy, it produces antibodies, from that moment on, against cocaine the moment the drug enters the body.”

In their first study in animals, the researchers injected billions of their viral concoction into laboratory mice, and found a strong immune response was generated against the vaccine. Also, when the scientists extracted the antibodies produced by the mice and put them in test tubes, it gobbled up cocaine. They also saw that mice that received both the vaccine and cocaine were much less hyperactive than untreated mice given cocaine.

In this study, the researchers sought to precisely define how effective the anti-cocaine vaccine is in non-human primates, who are closer in biology to humans than mice. They developed a tool to measure how much cocaine attached to the dopamine transporter, which picks up dopamine in the synapse between neurons and brings it out to be recycled. If cocaine is in the brain, it binds on to the transporter, effectively blocking the transporter from ferrying dopamine out of the synapse, keeping the neurotransmitter active to produce a drug high.

In the study, the researchers attached a short-lived isotope tracer to the dopamine transporter. The activity of the tracer could be seen using positron emission tomography (PET). The tool measured how much of the tracer attached to the dopamine receptor in the presence or absence of cocaine.

The PET studies showed no difference in the binding of the tracer to the dopamine transporter in vaccinated compared to unvaccinated animals if these two groups were not given cocaine. But when cocaine was given to the primates, there was a significant drop in activity of the tracer in non-vaccinated animals. That meant that without the vaccine, cocaine displaced the tracer in binding to the dopamine receptor.

Previous research had shown in humans that at least 47 percent of the dopamine transporter had to be occupied by cocaine in order to produce a drug high. The researchers found, in vaccinated primates, that cocaine occupancy of the dopamine receptor was reduced to levels of less than 20 percent.

“This is a direct demonstration in a large animal, using nuclear medicine technology, that we can reduce the amount of cocaine that reaches the brain sufficiently so that it is below the threshold by which you get the high,” says Dr. Crystal.

When the vaccine is studied in humans, the non-toxic dopamine transporter tracer can be used to help study its effectiveness as well, he adds.

The researchers do not know how often the vaccine needs to be administered in humans to maintain its anti-cocaine effect. One vaccine lasted 13 weeks in mice and seven weeks in non-human primates.

“An anti-cocaine vaccination will require booster shots in humans, but we don’t know yet how often these booster shots will be needed,” says Dr. Crystal. “I believe that for those people who desperately want to break their addiction, a series of vaccinations will help.”

Co-authors of the study include Dr. Anat Maoz, Dr. Martin J. Hicks, Dr. Shankar Vallabhajosula, Michael Synan, Dr. Paresh J. Kothari, Dr. Jonathan P. Dyke, Dr. Douglas J. Ballon, Dr. Stephen M. Kaminsky, Dr. Bishnu P. De and Dr. Jonathan B. Rosenberg from Weill Cornell Medical College; Dr. Diana Martinez from Columbia University; and Dr. George F. Koob and Dr. Kim D. Janda from The Scripps Research Institute.

The study was funded by grants from the National Institute on Drug Abuse (NIDA).

Thanks to Kebmodee and Dr. Rajadhyaksha for bringing this to the attention of the It’s Interesting community.

hunry

Over the last half decade, it has become increasingly clear that the normal gastrointestinal (GI) bacteria play a variety of very important roles in the biology of human and animals. Now Vic Norris of the University of Rouen, France, and coauthors propose yet another role for GI bacteria: that they exert some control over their hosts’ appetites. Their review was published online ahead of print in the Journal of Bacteriology.

This hypothesis is based in large part on observations of the number of roles bacteria are already known to play in host biology, as well as their relationship to the host system. “Bacteria both recognize and synthesize neuroendocrine hormones,” Norris et al. write. “This has led to the hypothesis that microbes within the gut comprise a community that forms a microbial organ interfacing with the mammalian nervous system that innervates the gastrointestinal tract.” (That nervous system innervating the GI tract is called the “enteric nervous system.” It contains roughly half a billion neurons, compared with 85 billion neurons in the central nervous system.)

“The gut microbiota respond both to both the nutrients consumed by their hosts and to the state of their hosts as signaled by various hormones,” write Norris et al. That communication presumably goes both ways: they also generate compounds that are used for signaling within the human system, “including neurotransmitters such as GABA, amino acids such as tyrosine and tryptophan — which can be converted into the mood-determining molecules, dopamine and serotonin” — and much else, says Norris.

Furthermore, it is becoming increasingly clear that gut bacteria may play a role in diseases such as cancer, metabolic syndrome, and thyroid disease, through their influence on host signaling pathways. They may even influence mood disorders, according to recent, pioneering studies, via actions on dopamine and peptides involved in appetite. The gut bacterium, Campilobacter jejuni, has been implicated in the induction of anxiety in mice, says Norris.

But do the gut flora in fact use their abilities to influence choice of food? The investigators propose a variety of experiments that could help answer this question, including epidemiological studies, and “experiments correlating the presence of particular bacterial metabolites with images of the activity of regions of the brain associated with appetite and pleasure.”

1.V. Norris, F. Molina, A. T. Gewirtz. Hypothesis: bacteria control host appetites. Journal of Bacteriology, 2012; DOI: 10.1128/JB.01384-12

http://www.sciencedaily.com/releases/2012/12/121219142301.htm