On the formation and functions of the neurons in the spinal cord that project axons to the thalamus, in rodent and primate
Assistant Professor, Department of Anesthesiology, University of Cinicinnati
Undergraduate Institution and Major/Degree:
University of New Orleans, BS, 2003
To protect the integrity of an organism a somatosensory system has evolved to respond to noxious stimuli. A critical component of this system in vertebrates is the neurons in the spinal cord which receive information from the periphery, integrate, and then distribute that information to supraspinal sites. Our research describes the function and hodology of these cells.
We have made several interesting and novel observations regarding the possible contributions of these cells to itch and pain:
1. Pruriceptive primate spinothalamic tract neurons respond either to histamine or to cowhage, a non-histaminergic pruritogen, suggesting multiple independent paths in the CNS for itch processing.
2. Scratching the receptive field of a spinothalamic tract neuron during a response to histamine produces inhibition, suggesting that part of the mechanism for relief from itch that is produced by scratching exists at the level of the spinal cord.
3. Spinal neurons that respond to itch producing agents send axons to several nuclei within the ventral posterior and posterior regions of the thalamus, indicating a target region of the brain that could be important for itch processing.
4. Spinothalamic tract neurons that respond to itch producing agents also respond to various other noxious stimuli such as heat, pinch, and the painful chemical capsaicin, indicating that these cells could play multiple roles in sensation.
Given the importance of the spinothalamic tract in transmitting information about pain, thermal sensation, and itch to the brain we have become interested in the development of this pathway during the fetal and the neonatal periods. To address questions about the genesis of the spinothalamic tract we have developed a simple technique permitting the injection of neural tracers into specific brain regions of fetal and neonatal mice in vivo. We have recently established that the gross structure of the spinothalamic tract is complete by the time of birth, however whether synaptic or functional connections are made is still unknown. We are also currently working to determine whether specific genes expressed in the spinal cord during development contribute to the differentiation of spinothalamic tract neurons.
- Davidson S, Moser H, Giesler G. Ascending pathways for Itch. In: Carstens E, Akiyama T, editors. Itch: Mechanisms and Treatment. Boca Raton (FL): CRC Press/Taylor & Francis; 2014. Chapter 22.
- Davidson S, Zhang X, Khasabov SG, Moser HR, Honda CN, Simone DA, Giesler GJ. Pruriceptive spinothalamic tract neurons: Physiological properties and projection targets in the primate. J Neurophysiol. 2012;108(6):1711-23.
- Davidson S and Giesler GJ Jr. Multiple pathways for itch and their interactions with pain. Trends Neurosci. 2010;33(12):550-8.
- Davidson S, Truong H, Giesler GJ Jr. A quantitative analysis of spinothalamic tract neurons in adult and developing mouse. J Comp Neurol. 2010;518:3193-204.
- Davidson S, Truong H, Nakagawa Y, Giesler GJ Jr. A microinjection technique for targeting regions of embryonic and neonatal mouse brain in vivo. Brain Res. 2010; 1307:43-52.
- Anderson GR, Cao Y, Davidson S, Truong HV, Pravetoni M, Thomas MJ, Wickman K, Giesler GJ Jr, Martemyanov KA. R7BP Complexes with RGS9-2 and RGS7 in the striatum differentially control motor learning and locomotor responses to cocaine. Neuropsychopharmacology 2010;35:1040-50.
- Davidson S, Zhang X, Khasabov SG, Simone DA, Giesler GJ Jr. Relief of itch by scratching: state-dependent inhibition of primate spinothalamic tract neurons. Nat Neurosci 2009;12:544-546.
- Davidson S, Zhang X, Khasabov SG, Simone DA, Giesler GJ Jr. Termination zones of functionally characterized primate spinothalamic tract neurons in posterior thalamus. J Neurophysiol 2008;100:2026-37.
- Davidson S, Zhang X, Yoon CH, Khasabov SG, Simone DA, Giesler GJ Jr. The itch-producing agents histamine and cowhage activate separate populations of primate spinothalamic tract neurons. J Neurosci. 2007 Sep 12;27(37):10007-14.
- Zhang X, Davidson S, Giesler GJ Jr. Thermally identified subgroups of marginal zone neurons project to distinct regions of the ventral posterior lateral nucleus in rats. J Neurosci. 2006;26:5215-5223.
Honors and Awards:
- Stark Award, 2007
- Hermann O Handwerker Award for Itch Research, 2007
- Richard Poppele Award, 2007
- National Research Service Award (F31), NINDS/NIH 2007-09
- National Graduate Student Research Festival, NIH, Bethesda, MD, 2008
- University of Minnesota Graduate School Bridge Award, 2008-09
- Milne and Brandenburg Award for Outstanding Graduate Research at the University of Minnesota, 2008
- Society for Neuroscience (2004-)
- American Association for the Advancement of Science (2007-)
- American Physiological Society (2008-)
- Brookline, Massachusetts