Signal path think about your mind
Signal path think about your mind skin#
A mosquito bite causes the body to release histamine in the area of the bite, turning the skin red and itchy. The VGLUT2 pathway, says Ma, likely quells excessive itching by activating certain inhibitory neurons in the spinal cord or brain.Ĭommon itches brought on by a chemical or mechanical stimulus-think mosquito bites and poison ivy-can be treated readily with agents that counteract histamine, a chemical the body produces to fight allergic reactions. “The mice began to scratch until they developed skin lesions.” “Removing VGLUT2 from pain-related sensory neurons in these mice weakened their responses to acute and chronic pain and caused the sensitization of multiple itch pathways,” says Ma. Essentially, Ma’s research team had created a mouse model that mimics some types of chronic itch in human patients. He discovered VGLUT2-deficient mice developed itch disorders as severe as those found in humans with chronic itch disorders.
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Ma came across this pain–itch dualism unexpectedly, while monitoring the behavior of mice that had been genetically altered to lose the action of VGLUT2 in a group of peripheral sensory neurons. This component is VGLUT2-dependent synaptic glutamate, a molecule that is released from certain sensory neurons and that serves as a transport for glutamate, the most abundant neurotransmitter in the brain. In a recent study published in the journal Neuron, Ma identified a neural component necessary for the pain sensation and itch suppression that also may help answer the “why do we itch?” question. This sudden drop suggests that the act of scratching calmed the STT neurons. But when the scientists used a device that mimics monkey fingers to scratch the itchy limbs, they saw a dramatic drop in STT neuronal activity. With each exposure, the monkeys’ STT neurons went wild. In their study, the researchers monitored spinal nerve activity in monkeys whose lower limbs had been exposed to itch-inducing histamine. This relays the information to the brain’s center for perceptual awareness, the sensory cortex. The STT transmits information about sensations, such as pain, temperature, touch-and, it turns out, itch-to the thalamus, deep within the brain. They showed that relief takes place deep within the spinal cord along the spinothalamic tract. In 2009, neuroscientists at the University of Minnesota identified part of the mechanism by which scratch relieves an itch. Previously, few studies focused on the neural mechanisms associated with itch, but several recently have succeeded in identifying a neural component to the itch sensation and its scratch response. ” She adds that the itch–scratch cycle most likely evolved to protect us from small, clinging threats-insects or plants-that can be avoided by withdrawal movements. “Pain is obvious and, without it, we wouldn’t live long-there would be nothing to prevent us from putting our hand into a fire or onto that hot burner. “These distinct behaviors likely developed to protect us against different types of threats,” saysĪnne Louise Oaklander, MD, PhD, an associate professor of neurology at HMS who studies chronic pain and itch. By contrast, when a piece of clothing brushes against your bare forearm, you scratch to quiet the irritation, giving little thought to the sensation and your reaction to it. Place your hand on a hot burner and you instantly pull it away the pain is intense. Itch and pain represent different sensations that evoke distinct behaviors. Itch runs along a neuronal interstate highway system that links the skin, the spinal cord, and the brain. Modern molecular, genetic, and anatomical studies now indicate that itch usually follows its own distinct course, says Qiufu Ma, PhD, an HMS professor of neurobiology who has studied the phenomenon. Itch, in fact, was considered a weakened form of pain.
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Recently, however, science has begun to enlighten us to the mechanisms at work in the itch–scratch cycle.įor years, the itch sensation was thought to travel along the same nerve pathway used by pain signals. Yet the question of why we itch and scratch in the first place has baffled researchers for years. Resources for those affected by War in UkraineĪs most of us know, a good scratch can satisfy an itch.Celebrating 50 Years of Diversity and Inclusion.Research Departments, Centers, Initiatives and more.