BRAINS IN BRIEFS
Scroll down to see new briefs about recent scientific publications by neuroscience graduate students at the University of Pennsylvania. Or search for your interests by key terms below (i.e. sleep, Alzheimer’s, autism).
My back hurts, my hand hurts: is pain different in different parts of the body?
or technically,
Sparse genetic tracing reveals regionally specific functional organization of mammalian nociceptors.
[See Original Abstract on Pubmed]
or technically,
Sparse genetic tracing reveals regionally specific functional organization of mammalian nociceptors.
[See Original Abstract on Pubmed]
Authors of the study: William Olson, Ishmail Abdus-Saboor, Lian Cui, Justin Burdge, Tobias Raabe, Minghong Ma, Wenqin Luo
Have you ever wondered why you can feel the details of an object with your fingertips, but not with your elbow? Your body detects sensations including touch and pain using specialized nerves that detect information in your environment and transmit it to your brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Together, these nerves are called the “sensory system.” As you may have noticed, however, this system does not treat all body regions the same. This is why your fingertips are much more sensitive to touch stimuli than other parts of your body (imagine trying to feel Braille with the back of your hand). Our fingertips are very sensitive to touch mainly because they contain more ‘touch-sensitive’ nerve endings than other body regions.
Pain perception relies on ‘pain-sensitive’ nerve endings that are distinct from our ‘touch-sensitive’ nerve endings. But just like for touch, certain regions of our body, like our fingertips, are more sensitive to pain than others. Interestingly, unlike for touch, this is not because we have more ‘pain-sensitive’ nerve endings in pain-sensitive areas. In fact, we have relatively few ‘pain-sensitive’ nerve endings in our fingertips -- even though they are extremely sensitive to pain! This observation surprised Will Olson, a neuroscience graduate student in Wenqin Luo’s lab. He wondered how certain parts of the body are more sensitive to pain than others.
To figure this out, he carefully studied the shape and size of pain nerve endings in mice. These nerves are like wires that run all the way from your skin into your spinal cord. This means there are two endings of these nerves: one in the skin and one in the spinal cord. Will took a good look at both ends. He saw that, in general, ‘pain-sensitive’ nerves come in different shapes and sizes depending on where in the body they are found. Interestingly, he found that pain nerve endings have a low density in the mouse paw, just like in the human hand! The pain nerve endings in the paw also looked very similar to pain nerve endings in other parts of the mouse. This surprised Will because he knew that mice have very high pain sensitivity in their paws. He wondered, if the density and the shape of the pain nerves in the paw skin is the same as in other parts of the body, then why are paws so sensitive to pain?! The answer became clear when Will looked at these nerves in the spinal cord -- in the spinal cord, paw pain nerves look completely different from pain nerves that come from other parts of the mouse. Will hypothesized that the special shape of these paw pain nerves could enhance pain sensation in the paw. And in fact, Will found that these paw pain nerves are better at sending information to the spinal cord than pain nerves that come from other parts of the mouse.
While these findings are interesting and could even help some of us decide on the least painful place to get a tattoo, this study might also help people with chronic pain. Chronic pain occurs when people feel pain for weeks, months or even years. Based on this study, we may be able to identify specific causes of chronic pain in different parts of the body. For example, chronic back pain might be very different from chronic joint pain. Our current pain medications are not effective as treatments for many forms of chronic pain. The lack of good treatments has contributed to the increase in opioid prescriptions that led to opioid addiction crisis. Identifying more specific causes of chronic pain could give researchers ideas for better ways to treat it.
Pain perception relies on ‘pain-sensitive’ nerve endings that are distinct from our ‘touch-sensitive’ nerve endings. But just like for touch, certain regions of our body, like our fingertips, are more sensitive to pain than others. Interestingly, unlike for touch, this is not because we have more ‘pain-sensitive’ nerve endings in pain-sensitive areas. In fact, we have relatively few ‘pain-sensitive’ nerve endings in our fingertips -- even though they are extremely sensitive to pain! This observation surprised Will Olson, a neuroscience graduate student in Wenqin Luo’s lab. He wondered how certain parts of the body are more sensitive to pain than others.
To figure this out, he carefully studied the shape and size of pain nerve endings in mice. These nerves are like wires that run all the way from your skin into your spinal cord. This means there are two endings of these nerves: one in the skin and one in the spinal cord. Will took a good look at both ends. He saw that, in general, ‘pain-sensitive’ nerves come in different shapes and sizes depending on where in the body they are found. Interestingly, he found that pain nerve endings have a low density in the mouse paw, just like in the human hand! The pain nerve endings in the paw also looked very similar to pain nerve endings in other parts of the mouse. This surprised Will because he knew that mice have very high pain sensitivity in their paws. He wondered, if the density and the shape of the pain nerves in the paw skin is the same as in other parts of the body, then why are paws so sensitive to pain?! The answer became clear when Will looked at these nerves in the spinal cord -- in the spinal cord, paw pain nerves look completely different from pain nerves that come from other parts of the mouse. Will hypothesized that the special shape of these paw pain nerves could enhance pain sensation in the paw. And in fact, Will found that these paw pain nerves are better at sending information to the spinal cord than pain nerves that come from other parts of the mouse.
While these findings are interesting and could even help some of us decide on the least painful place to get a tattoo, this study might also help people with chronic pain. Chronic pain occurs when people feel pain for weeks, months or even years. Based on this study, we may be able to identify specific causes of chronic pain in different parts of the body. For example, chronic back pain might be very different from chronic joint pain. Our current pain medications are not effective as treatments for many forms of chronic pain. The lack of good treatments has contributed to the increase in opioid prescriptions that led to opioid addiction crisis. Identifying more specific causes of chronic pain could give researchers ideas for better ways to treat it.
About the brief writer: Patti Murphy
Patti is a PhD Candidate in Michael Granato's lab. Patti is interested in understanding and developing therapeutics for functional nerve regeneration, particularly to restore voluntary motor control after spinal cord injury.
Do you want to learn more about how we feel pain? You can read Will’s entire paper here.
Highway to the brain: cells responsible for touch need a support system to grow really long distances during development
or technically,
Roof Plate-Derived Radial Glial-like Cells Support Developmental Growth of Rapidly Adapting Mechanoreceptor Ascending Axons
[See Original Abstract on Pubmed]
or technically,
Roof Plate-Derived Radial Glial-like Cells Support Developmental Growth of Rapidly Adapting Mechanoreceptor Ascending Axons
[See Original Abstract on Pubmed]
Authors of the study: Kim Kridsada, Jingwen Niu, Zhiping Wang,Parthiv Haldipur, Long Ding, Jian J. Li, Anne G. Lindgren, Eloisa Herrera, Gareth M. Thomas, Victor V. Chizhikov, Kathleen J. Millen, and Wenqin Luo
Have you ever thought about going on a cross-country road trip, perhaps from Washington D.C to San Francisco? To make traveling such a long distance easier, you may need road signs telling you where to go and highways to make your journey more direct. In the same way that we need directions and fuel for a long trip, the neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles that mediate our sense of touch (also known as mechanoreceptorA type of neuron (nerve cell) that senses mechanical stimuli like touch cells) need a way to get their axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. from the periphery of your body (e.g., hands, toes, and legs) to their final destination, the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.! During nervous system development, it’s really important for these cells to reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. in order to provide us with a proper sense of touch; these cells help you feel the carpet under your feet as you get out of bed, the fork in your hand as you eat your lunch, and even that light tap on your shoulder when somebody is trying to get your attention. So how exactly do these touch neuronA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. travel so far to ultimately reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.? Kim Kridsada, a neuroscience graduate student in Wenqin Luo’s lab, sought to figure this out.
Kim noticed that during development, the mechanoreceptorA type of neuron (nerve cell) that senses mechanical stimuli like touch (“touch”) cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that had to travel the farthest (e.g. from hands and feet to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.) also seemed to grow closer to a group of specialized cells in the spinal cord compared to cells that didn’t have as far to go. She thought that maybe these specialized cells could be guiding cells (aka acting as a highway) and also sending signals (aka “road signs”) out to the touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that helped them grow through the spinal cord to eventually reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Kim found that these support cells indeed sent out signals, in the form of specific growth-promoting proteinsAn essential molecule found in all cells. DNA contains the recipes the cell uses to make proteins. Examples of proteins include receptors, enzymes, and antibodies., that could be used by the touch neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles to grow in the correct directions. The support cells that Kim found surrounding these touch cells were part of a particular class of cells known as radial glial-like cells (RGLCs), which are cells that can help with growth and development of neuronal cells. Kim wondered how important these RGLCs were for the touch cells - did the touch cells need them to grow along this highway to reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.? She hypothesized that without this RGLC highway, the touch cells wouldn't grow as far. To test whether RGLCs are truly needed in the body for touch cells to grow long distances, Kim studied mice that did not have any RGLCs but still had touch cells that were capable of growing. Interestingly, she found that in mice that had no RGLCs, their touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. were much shorter and 40% of their touch cells did not grow long enough to reach their correct destination in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.! Taken together, these findings suggest that RGLCs are really important in the body for helping touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. eventually make their way to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals..
Overall, Kim discovered a previously unknown group of support cells (RGLCs) in the spinal cord that help touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. make connections over long distances, from the periphery of the body to eventually the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. These findings are really important not only for our understanding of how we develop a very important sense (touch), but could also be used to improve regeneration in people who have suffered injuries and have, as a result, lost their sense of touch. Thanks to Kim’s work, we now know that these spinal cord cells help certain touch cells grow long distances, so we could try to develop drugs or therapies that target them so that growth of touch cells during regeneration happens more easily.
Kim noticed that during development, the mechanoreceptorA type of neuron (nerve cell) that senses mechanical stimuli like touch (“touch”) cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that had to travel the farthest (e.g. from hands and feet to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.) also seemed to grow closer to a group of specialized cells in the spinal cord compared to cells that didn’t have as far to go. She thought that maybe these specialized cells could be guiding cells (aka acting as a highway) and also sending signals (aka “road signs”) out to the touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. that helped them grow through the spinal cord to eventually reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. Kim found that these support cells indeed sent out signals, in the form of specific growth-promoting proteinsAn essential molecule found in all cells. DNA contains the recipes the cell uses to make proteins. Examples of proteins include receptors, enzymes, and antibodies., that could be used by the touch neuronsA nerve cell that uses electrical and chemical signals to send information to other cells including other neurons and muscles to grow in the correct directions. The support cells that Kim found surrounding these touch cells were part of a particular class of cells known as radial glial-like cells (RGLCs), which are cells that can help with growth and development of neuronal cells. Kim wondered how important these RGLCs were for the touch cells - did the touch cells need them to grow along this highway to reach the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.? She hypothesized that without this RGLC highway, the touch cells wouldn't grow as far. To test whether RGLCs are truly needed in the body for touch cells to grow long distances, Kim studied mice that did not have any RGLCs but still had touch cells that were capable of growing. Interestingly, she found that in mice that had no RGLCs, their touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. were much shorter and 40% of their touch cells did not grow long enough to reach their correct destination in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.! Taken together, these findings suggest that RGLCs are really important in the body for helping touch cells axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. eventually make their way to the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals..
Overall, Kim discovered a previously unknown group of support cells (RGLCs) in the spinal cord that help touch cell axonsA specialized part of a neuron that sends electrical and chemical signals to other cells. Axons are typically long and thin like a wire. make connections over long distances, from the periphery of the body to eventually the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.. These findings are really important not only for our understanding of how we develop a very important sense (touch), but could also be used to improve regeneration in people who have suffered injuries and have, as a result, lost their sense of touch. Thanks to Kim’s work, we now know that these spinal cord cells help certain touch cells grow long distances, so we could try to develop drugs or therapies that target them so that growth of touch cells during regeneration happens more easily.
About the brief writer: Elelbin Ortiz
Elelbin is a PhD Candidate in Michael Granato’s lab. She is interested in understanding how animals set behavioral thresholds, or ways to decide whether information from the environment requires a response or not. She is interested in understanding how an animal's genes (DNA) influence how these behavioral thresholds are set.