Pain after Injury

A research has been conducted by investigators at Harvard Medical School, as a result of which it is found that there is a set of neurons that lead to sustained pain and resulting pain-coping behaviours A separate neural pathway exists that regulate threat avoidance versus injury mitigation. The study shows the different pathways that drive reflexive withdrawal to avoid injury and the subsequent pain-coping responses.

Along with the past research results and the clinical observations of patients with neurological damage clearly show the distinct brain regions that differentiate between the reflexive withdrawal from a skin prick and the long-lasting pain arising from tissue injury caused by the pinprick. For example, let’s say a toddler puts her hand on a hot stove and swiftly withdraws; the finger will have a minor burn and then the toddler puts she puts the burned finger in her mouth to feel better as it is painful. Now here, if you observe, withdrawing one's hand to avoid injury and soothing the pain of that injury are two distinct evolutionary responses, but the scientists are not aware if their molecular origins and signalling pathways. The study has been successful to tell on how these responses arise outside the brain. The researchers have stated that most current methods are based on measuring the initial, reflexive response that serves to avert tissue injury and not on measuring the lasting pain that arises from actual tissue damage. They also say that few drug compounds might have been successful in relieving the sustained pain leaving the lasting sensation of pain that immediately follows injury. A study senior author Qiufu Ma, professor of neurobiology in the Blavatnik Institute at Harvard Medical School and a researcher at Dana-Farber Cancer Institute, stated that "The ongoing opioid crisis has created an acute and pressing need to develop new pain treatments, and our findings suggest that a more tailored approach to assessing pain response would be to focus on sustained pain response rather than reflexive protective withdrawal. All these years, researchers may have been measuring the wrong response". Earlier also, Ma and colleagues, found and highlighted the existence of two sets of peripheral neurons, that is, nerve cells located outside the brain and spinal cord. One set of peripheral nerve cells send and receive signals exclusively to and from the superficial layers of the skin whereby another set of neurons are dispersed throughout the body to drive the lasting pain that sets in after initial injury and induces pain-coping behaviours. Later a set of neurons called Tac1, that is, a cluster of nerves located at the lower end of the spinal cord that transmit signals between the brain and the rest of the body, were examined in which the team assessed pain response in two groups of mice, one with intact Tac1 neurons and another with chemically disabled Tac1 neurons. The results confirmed that Tac1 neurons are critical for pain-coping behaviours. Post this Ma and team said "We believe that Tac1 neurons act as a relay station that dispatches pain signals from the tissue, through Trpv1 nerve fibres all the way to the brain".

By: Anuja Arora

Content: https://www.sciencedaily.com/releases/2018/12/181213142209.htm