In a study published in Science, researchers at Karolinska Institutet describe the neural processes behind how morphine relieves pain. This is valuable knowledge because the drug has such serious side effects. Morphine is a powerful painkiller that belongs to the group of opioids.
It blocks signals in the pain pathways and also increases feelings of pleasure. Morphine acts on several central and peripheral pain pathways in the body, but the neural processes behind the pain relief have not previously been fully understood. Researchers have now investigated how morphine relieves pain using several new experimental approaches.
They have exposed laboratory animals to morphine and then managed to "capture" the neurons that the morphine activated in the animals. This allowed the researchers to identify, classify and synthetically control the neurons in the neural pathways involved in pain relief. Morphine activates a 'morphine ensemble ' The researchers discovered that morphine affects a selected set of neurons in the brain in the part called the rostral ventromedial medulla (RVM).
Together, these neurons form a kind of 'morphine ensemble'. This is a group of neurons whose change in activity leads to pain relief. When the researchers synthetically inactivated the neurons in this group, they completely abolished the effects of morphine on pain.
When they reactivated the neurons, they were able to similarly recreate the pain relief. A particular type of neuron that wires to the spina.