Researchers identify rodent brain circuits that can contribute to the negative emotional aspects of pain-ScienceDaily

New research announced today Nature Neuroscience Revealed neural circuits in the rodent brain. It can play an important role in mediating pain-induced anhedonia. This is a diminished motivation to carry out reward-driven actions. In a study funded by the National Institute on Drug Abuse (NIDA), which is part of the National Institute of Health, researchers modified the activity of this circuit and motivated it with a preclinical model of pain tested in rodents. I was able to recover the level of.

At a basic level, pain has two components: sensations (feeling pain) and emotions (negative emotional elements of pain). The presence of anhedonia, a hallmark of emotional pain, is a common feature of depression and may also increase vulnerability to opioid use disorder (OUD). Given this relationship, a better understanding of the brain circuits involved in the emotional component of pain is an important part of NIDA’s research portfolio.

“Chronic pain has been experienced at many levels, not just physically, and this study provides the biological basis for emotional pain. Psychological phenomena such as emotional pain are the result of biological processes. It reminds me of something, “said NoraD’s NIDA director. .Volkow, MD “It’s exciting to see the beginning of a path of progress that may pave the way for therapeutic interventions that address pain motivation and emotional effects.”

Researchers at Washington University in St. Louis observe that painful rats are more likely to consume higher doses of heroin than painless rats to investigate what underlies the emotional component of pain. Based on previous studies. In addition, their motivation for natural rewards such as sugar tablets has diminished. A new series of studies sought to uncover the brain circuits involved in this pathway and better understand the relationship between pain and its associated changes in motivational state.

In this new study, researchers measured the activity of dopamine neurons in the ventral tegmental area, which is part of the brain’s “reward system” that processes rewards and regulates motivated behavior. Dopamine neuron activity was measured while the rat was pressing the lever with its forefoot and receiving a sugar tablet (reward). To assess the effects of pain on the behavior and activity of these dopamine neurons in animals, either saline (control condition) or a solution that causes local inflammation (pain condition) was injected into the hind paw.

Forty-eight hours later, researchers found that painful rats pressed the lever less often, resulting in sugar tablets. This indicates a decrease in motivation and a decrease in the activity of dopamine neurons. The reason for the subsequent decrease in dopaminergic neuron activity is that pain activates cells from a region of the brain known as the rostral tegmental nucleus (RMTg) that makes inhibitory neurochemical GABA, and GABA activates dopaminergic neurons. I found it to block. ..

However, when researchers artificially regained the activity of dopamine neurons (through a process called chemogenetics), they reversed the negative effects of pain on the reward system, motivating them to push the lever of sugar tablets among rats. Pain, even if painful stimuli were still present.

In additional experiments, researchers were also able to restore dopamine neuron activity by reversing pain-induced hyperactivity in GABA neurons. Doing so regained motivation for the painful rats to prefer a sweeter solution of sucrose to water, indicating an improved ability to feel joy despite the pain. increase.

As far as the authors know, this is the first time it has been reported that pain promotes increased activity of GABA neurons and “inhibitory pathways” of the brain’s reward system from RMTg, causing decreased activity of dopamine cells.

“Pain is mainly studied in peripheral areas rather than in the brain and aims to reduce or eliminate the sensory components of pain, while the emotional components of pain and depression, anxiety, and sensory abilities. Related comorbidities such as lack The joy associated with pain has been largely ignored. “

“It’s great to be able to show painful patients that changes in mental health and behavior are as realistic as physical sensations, and one day we may be able to treat these changes.” Research author Dr. Megan Creed added. Washington University in St. Louis.

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