For the last two years, Dr. Zhou-Feng Chen has been researching matters of tolerance and addiction to opiates. Now he may have found something to assist patients’ problems with this class of drugs that includes morphine and its pain killing effects.

Chen, associate professor in the departments of Anesthesiology, Psychiatry, Molecular Biology and Pharmacology, focuses his research on serotonergic neurons, a very small group of neurons located in the hindbrain.

The group only contains a few thousand cells, but their axons extend to several places. As Chen believes, certain situations such as stress heighten the importance of these neurons.

The 5-HT neurons are very important in the pain killing effect, but play no role in addiction. He says that if the 5-HT neurons are removed, the drugs lose their analgesic effect.

“If you remove those neurons, the analgesic effect is not as effective as it is supposed to be,” said Chen. “However, we found that this population of neurons is not involved in tolerance and they are also not involved in morphine reward which means there must be other things mediating those side effects. Those neurons only mediate the good aspect of the analgesic effect.”

Many students were glad to see that the research provided insight into what makes pain medication addictive.

“It represents a powerful advantage for technology in pharmaceuticals,” said junior Clint Morgan.

Freshman Angie Gao agreed that the research will have positive effects.

“It could be a really good thing for people with chronic pain problems,” said Gao. “Once [patients] get better they won’t have to keep taking them.”

Despite the benefits from the research, several students also noted that it may lead to increased use of pain medication.

“If I’m not worried about getting addicted, I might take them more,” said freshman Andrew Frangos.

Chen cautions that opiates have several side effects that were not targeted in the research and that people need to make good decisions concerning pain killers.

“Pain killers will always have side effects,” he said. “We may be able to increase pain killing effect while minimizing the side effect. It’s a little bit misleading. It is not likely that we will find a drug or find a pain killer with no side effects. There are many different things involved in analgesic effect or tolerance. We just tried to look at how [these neurons] are involved in these processes. [There are] many side effects, but here we only addressed two. They have side effects we didn’t talk about.”

In the future, it may be possible to target the 5-HT neurons in order to maximize the analgesic effect while minimizing the negative effects such as addiction.

According to Chen, the study was originally interested in how neurons develop. A gene known as Lmx1b was identified as being important to the development of neurons.

In order to study the effects of the drugs, mice had the Lmx1b gene removed from the 5-HT neurons.

“[The gene] is so important that if you delete this gene, the neurons die,” he said. “We removed the gene only in those neurons. If you completely knock out the gene, the mice will die because genes have multiple functions.”

Chen says the mice can survive when the gene is only removed from the specific group of neurons. The mice’s preference of morphine was tested using an apparatus with two chambers. In one chamber the mice received morphine and in the other chamber the mice received a saline solution.

The mice lacking 5-HT neurons preferred the chamber where they received morphine even though they did not get the same effect from the morphine.

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