Tag Archives: Reward system

Drugs lead to brain brake failure

 A single dose of morphine was found to lower the inhibitions of rats, even after the drug had left their systems, a finding that may help scientists better understand addiction in humans, US researchers said.

In rats, the painkiller blocked the brain’s ability to strengthen connections, or synapses, that ratchet down reward or pleasure, researchers from Brown University reported in the journal Nature.

“What we have found is that the inhibitory synapses can no longer be strengthened 24 hours after treatment with morphine, which suggests that a natural brake has been removed,” said Julie Kauer, a professor of molecular pharmacology, physiology and biotechnology at Brown.

“This happens 24 hours after the animal had one dose of morphine. There is no morphine left in the brain. It shows that it is a persistent effect of the drug,” she said in a telephone interview.

Kauer said the finding adds to a growing body of evidence suggesting a link between learning and addiction and may help in the development of drugs to treat addiction. “Strengthening synapses, we think, is the beginning of the formation of memory,” she said.

By shutting off the natural ability to strengthen connections that inhibit pleasure, the brain may be learning to crave drugs, she said.

Kauer said the brain has two kinds of neurons  those that excite the nerve connections and those that inhibit or depress them.

“If inhibition is reduced, you get runaway excitability,” she said. This imbalance may boost the firing of neurons that make dopamine, the brain’s “pleasure chemical” activated after rewarding experiences such as eating, sex, and the use of addictive drugs.

Kauer found the changes in a small section of the midbrain that is involved in the reward system. While her study looked at the early response to addictive drugs, she intends to study the effect over time.

Source:The Times Of India

Food may be like a drug for some

 The same brain circuits are involved when obese people fill their stomachs as when drug addicts think about drugs, a finding that suggests overeating and addiction may be linked, US researchers reported on Monday.

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The finding may help in creating better treatments for obesity a growing problem in the US and elsewhere.

“We wanted to know why, when people are already full, why people are still eating a lot,” said Dr Gene-Jack Wang of Brookhaven National Laboratory in Upton, New York.

“We were able to simulate the process that takes place when the stomach is full, and for the first time we could see the pathway from the stomach to the brain that turns “off” the brain’s desire to continue eating.”

Wang and colleagues tested seven obese volunteers who had been fitted with a gastric stimulator a device that tricks the body into thinking the stomach is full.

They used a PET scan to see which parts of the brain activated when the stimulator was activated. “We thought the activated area (of the brain) must be in the satiety centre,” Wang said. “We saw a lot of activity in all areas of the brain, especially in the hippocampus.”

The gas stimulators also sent messages of satiety to brain circuits in the orbitofrontal cortex and striatum, which have been linked to craving and desire in cocaine addicts.

“This provides further evidence of the connection between the hippocampus, the emotions, and the desire to eat, and gives us new insight into the mechanisms by which obese people use food to soothe their emotions,” said Wang.

(From the news published in The Times Of India)