Researchers explain the brain mechanisms that enable morphine to alleviate pain. Understanding these mechanisms is crucial given the serious side effects associated with the medication.
In a research article published in Science, scientists from Karolinska Institutet elucidate the brain mechanisms that allow morphine to reduce pain. This information is essential because the drug can lead to significant side effects.
Morphine is a potent analgesic categorized as an opioid. It interrupts pain signaling and enhances feelings of pleasure. While morphine targets numerous pain pathways in both the central and peripheral nervous systems, the specific neural mechanisms responsible for its pain-relieving effects have not been thoroughly clarified until now.
The research team explored how morphine alleviates pain through various innovative experimental methods. They administered morphine to lab animals and subsequently “captured” the neurons activated by the drug. This enabled them to identify, classify, and control the neurons involved in pain relief within the neural pathways.
Morphine operates through a ‘morphine ensemble’
The investigators found that morphine influences a specific cluster of neurons in the brain region known as the rostral ventromedial medulla (RVM). Collectively, these neurons form what is referred to as a ‘morphine ensemble.’ This collection of neurons, when activated, contributes to alleviating pain.
When the researchers artificially inactivated the neurons in this cluster, the pain-relieving effects of morphine were entirely eliminated. Conversely, reactivating the neurons successfully reintroduced the pain relief.
A particular type of neuron that connects to the spinal cord plays a crucial role within this ‘morphine ensemble.’ These spinal cord neurons link to inhibitory neurons that diminish pain signaling, ultimately preventing pain sensation.
Potentially dangerous medication
In medical settings, morphine carries significant risks, including addiction, misuse, overdose, and even death.
“Finding ways to manage pain without causing these severe side effects has proven challenging,” remarks Patrik Ernfors, a professor at the Department of Medical Biochemistry and Biophysics at Karolinska Institutet and the study’s lead researcher.
He and his team aspire that their increased understanding of morphine’s bodily functions can inform strategies for minimizing these side effects in the future.
“This research is important because it sheds light on the neural pathways and cells involved, offering insights into morphine’s strong pain-relieving capabilities. It may also clarify how these mechanisms differ from those associated with feelings of euphoria, well-being, and potential addiction,” explains Patrik Ernfors.
The next phase of their research will delve into why the efficacy of pain relief tends to diminish with prolonged morphine usage.
This study was supported by funding from the Swedish Research Council, the European Research Council, and the Knut and Alice Wallenberg Foundation.
