By Janet Fang
Posting in Energy
An anesthetic could be an anti-depressant that works within just hours. And a nicotine-based drug could help you stop eating, without triggering the need for tobacco.
Scientists have puzzled out why two noted molecules do the things they do.
It's sometimes taken as a hallucinogen – as a club drug called ‘Special K’ – and at high doses, it’s a widely-used anesthetic. Researchers are now figuring out why ketamine also has fast-acting, antidepressant-like effects as well.
This could be a direct target for quick-acting treatments of major depression.
Traditional antidepressants, like Zoloft or Paxil, often take weeks or months to have an effect – a major drawback for treating high-risk individuals. A single low dose of intravenous ketamine, on the other hand, can alleviate major symptoms within hours, with effects lasting up to 2 weeks.
When put in a tub of water, mice considered depressed quickly give up escape attempts and float motionless. Half an hour after receiving a dose of ketamine, mice swim for a longer period of time.
But what goes on in their brains was unclear. Scientists knew that ketamine binds to, and blocks, a receptor in the brain called NMDAR, which triggers its anesthetic effects.
Now, a team led by Lisa Monteggia from University of Texas Southwestern Medical Center found that by blocking NMDARs in mice, the depression lessened.
- Blocking NMDARs with ketamine causes neurons to make more of a protein called brain-derived neurotrophic factor (BDNF) – a nerve growth factor that supports the health of brain cells, helping them grow and promoting the development of new neurons. And it’s linked to antidepressant effects.
- Ketamine causes the rapid synthesis of BDNF by deactivating a chemical called eEF2 kinase, which normally suppresses BDNF.
"We've identified a novel pathway never before linked to any behavior, let alone an antidepressant response," says Monteggia, "that could be a novel drug target."
Drugs that inhibit eEF2 kinase could become antidepressants that work faster than any current medication.
The study was published in Nature this week.
Smokers are, on average, thinner than non-smokers; they also tend to put on weight after they quit. That’s because nicotine decreases appetite. And researchers now show that that’s because nicotine activates a certain group of neurons in the brain.
A team led by Marina Picciotto of Yale focused on one particular nicotine receptor, dubbed α3β4. Mice who received drugs engineered to stimulate only α3β4 receptors were eating less.
In fact, mice who received the drug binding to α3β4 receptors ate half the amount of food as untreated mice in 2 hours after administering the drug. Their body fat dropped 15% to 20% over 30 days.
- Nicotine activates certain receptors to influence a collection of central nervous system circuits in the hypothalamus, a brain region involved in eating behavior (the one that sends “I’m full” messages after meals).
- Those receptors increase the activity of POMC neurons, which affect obesity in humans.
These nicotine receptors are involved in the fight-or-flight response that occurs when animals encounter a threat: these responded to nicotine in a way that reduced hunger.
Evolutionarily, "the fight-or-flight response is one where you actually want to preserve your energy to do something very important," Picciotto says. "So maybe you don't want to be out there eating while you're supposed to be running away from a tiger."
So smoking remains a leading cause of preventable death, and this study suggests that nicotine-based treatments could help people quit smoking and control their obesity or metabolic disorders.
"Imagine a nicotine-based medicine which could only target those cells which stop eating and not trigger the need for tobacco," Picciotto says.
The study was published in Science last week.
Jun 16, 2011
It would seem that nicotine gums and patches are much safer than smoking. If they were not classed as medical devices, they might even be more affordable than smoking. Unfortunately, since they are so classified, they are priced as a medication. This discourages their use to replace tobacco, causing unnecessary risk to the people.
I agree with the comment before me, it is the nicotine that is addictive... the poison that they put in the tobacco is the cause of cancer not the tobacco itself...., what about the chemical treated water that we drink, the chemical polluted food that we eat, the polluted air that we breathe and so on, those are also things that do poison us and makes us sick on an everyday basis, they wont talk about it though, it's easier to put all the blame on tobacco smoking when it comes to health problems, i'm not trying to excuse my bad habit of smoking here, just saying things as they really are. P.S. When will they close down all the tobacco companies. ???
It's not the nicotine that causes the health related problems with cigarette smoking, it's the vast number of poisons released when smoking and inhaling a cigarette. Yes, the nicotine itself is addictive, but that's not what causes all the other health related problems associated with cigarette smoking. Studies show that nicotine based anti-smoking treatments (such as gum, patches and lozenges) work to minimise the nicotine addiction, but do NOT contribute to all the other health related problems with cigarette smoking.
Has anybody done the math on nicotine and heart attacks: do you gain more from weight loss than you lose from the increased risk of taking the poison? -dlj.
Kid you not. Reported in the New Scientist this week. However the effect has been noticed since 2007 however it is becoming more common along with the drug use. http://en.wikipedia.org/wiki/Ketamine
...it's the other parts OF tobacco which are bad for you. Not nicotine, nor anything "added". A cigarette company which could launch a danger-free cigarette would gain roughly 100% market share - if they could do this simply by not "adding poisons", what would be the motivation not to?