Charles J. Woodbury - US grants

[unreadable] DESCRIPTION (provided by applicant): Pain circuitry in the spinal cord develops over a prolonged period of late fetal and early postnatal life and is particularly vulnerable to tissue trauma and inflammation during this time. Over the first few weeks of postnatal life, the central terminals of myelinated primary afferents undergo significant reorganization to generate the stereotypical laminar termination patterns seen in the adult dorsal horn. Recent findings in newborn mice have revealed that tactile afferents generate strikingly adult laminar termination patterns early on and thus undergo little central reorganization postnatally. By contrast, myelinated nociceptors give rise to widespread, inappropriate central projections in early postnatal life and thus the characteristic adult termination patterns of these afferents appear to mature later. Due to the relative immaturity of myelinated nociceptor central projections in newborns, the subsequent postnatal maturation of this group of afferents may be acutely susceptible to early perturbations of the periphery. [unreadable] [unreadable] The proposed experiments will examine the postnatal time course over which myelinated nociceptors achieve maturity to determine the potential window of this vulnerability. These studies will address the hypothesis that this early central exuberance is normally transient but that early tissue trauma, such as that caused by persistent tissue inflammation, arrests the normal postnatal reorganization of their central anatomy, leading to permanent structural alterations in spinal pain circuitry. An isolated somatosensory system preparation developed for comprehensive analyses of individual skin sensory neurons will be used to study the postnatal maturation of myelinated nociceptors in both hairy and glabrous skin of mice. A model of adjuvant-induced inflammation in glabrous skin of newborn mice will be used to examine the effects of early tissue trauma on the anatomical, physiological, and neurochemical maturation of individual neurons. Through intracellular recordings, neurons will be physiologically characterized using a variety of natural skin stimuli and then labeled in their entirety through iontophoresis of Neurobiotin. Their central projections will be reconstructed and analyzed morphometrically for changes taking place throughout postnatal maturation. Somata will be analyzed immunocytochemically to determine neurochemical changes, and peripheral endings will be analyzed for correlated structural changes in both normal and traumatized skin. The results of these studies will provide a detailed understanding of the early maturation of this vital component of the pain system, and the susceptibility of these afferents to early perturbation. This information will be pivotal to the development of future strategies in pediatric pain management and the translation of these strategies into effective practice.

nociceptors; developmental neurobiology; biological signal transduction;

DESCRIPTION (provided by applicant): Pain sensory neurons, or nociceptors, are particularly vulnerable to tissue trauma and inflammation during early life, and there is mounting evidence that peripheral inflammation in newborns can lead to permanent alterations in central nociceptive circuitry and pain-related behaviors. The extent to which these changes reflect permanent local alterations in the peripheral terminals of nociceptors is unknown, although such knowledge is critical to understanding causal mechanisms that either drive or help maintain altered nociceptive functioning in adults. Our recent work in neonatal mice has shown that the peripheral terminals of myelinated nociceptors undergo dramatic anatomical and physiological alterations within days of an inflammatory insult;by contrast, other cutaneous nociceptors were largely unaffected, and thus effects on myelinated nociceptors may be key to understanding altered adult pain states following early tissue trauma. The proposed experiments will directly examine the potential for permanent changes in myelinated nociceptor terminals using an in vivo trigeminal preparation in adult mice. This new preparation confers the ability, for the first time, to label the peripheral terminals of physiologically identified skin sensory neurons in adult animals. The overall goals of these studies are to determine the morphological diversity of myelinated nociceptor terminals in the skin of normal adult animals, and whether peripheral inflammation in early neonatal life results in permanent alterations of these endings. Through intracellular recordings, neurons will be physiologically characterized using a comprehensive suite of natural skin stimuli and then labeled in their entirety through iontophoresis of Neurobiotin. The peripheral terminals of labeled neurons will be reconstructed in skin sections to allow direct confirmation of functional morphology of individual physiologically identified skin sensory neurons. Analyses in normal (i.e., naove) adults will provide a critical backdrop for analyzing potential changes in these endings following neonatal inflammation. Potential long-term alterations in peripheral endings will be examined in two different models of experimentally induced inflammation in facial skin of newborn mice;the long-term effects of neonatal adjuvant-induced and carrageenan-induced inflammation will be compared to analyze potential differences between persistent versus acute inflammatory states in producing permanent alterations in myelinated nociceptor terminals. These results will be compared with the effects of experimentally induced inflammation in adulthood to determine whether the peripheral terminals of myelinated nociceptors retain the ability to respond to adult tissue trauma and therefore remain plastic throughout life. The results of these studies will provide an unprecedented understanding of the early maturation of this vital component of the pain system and the susceptibility of these afferents to early perturbation. This information will be pivotal to the development of future strategies in pediatric pain management and the translation of these strategies into effective practice. PUBLIC HEALTH RELEVANCE There is mounting evidence that peripheral inflammation in newborns can lead to permanent alterations in pain circuitry and behaviors. The extent to which these permanent effects are driven by irreversible effects of early inflammation on the terminals of pain-sensing, or nociceptive sensory neurons in the skin is unknown. The proposed work will determine the morphological diversity of nociceptor terminals in the skin of normal adult mice, and determine whether early inflammation leads to in permanent alterations in these endings.

Muscle pain and fatigue affect nearly all people at some time in their lives. At present, effective treatments for short term muscle pain are clearly inadequate and adequate treatment for chronic muscle pain is even worse. Considerable evidence indicates that peripheral sensory dysregulation of group III/IV muscle afferents, and autonomic dysregulation may cause or contribute to both short-term and chronic muscle pain and fatigue.Our long term goal is to determine the fundamental mechanisms that signal intense muscle pain, ache and fatigue to sensory and motor systems. We have previously used discoveries in mouse models to prove that combinations of protons, lactate, and ATP are necessary and sufficient to activate muscle sensory neurons. In translational studies in human subjects we showed that combination of these three metabolites activated the sensations of muscle ache and fatigue in human subjects. We propose here to use several transgenic mice that will make it possible, for the first time, to determine the molecular, cellular, and structural mechanisms of the sensory signaling pathways for the cognitive sensations of muscle pain and muscle fatigue. These mice will also make it possible for us to determine the many different types of afferents that selectively signal the many different aspects of autonomic function that allow us to function over a wide range of muscle blood flow. Finally, these mice will make it possible for us to directly image not only the cell bodies of the muscle innervating neurons, but to directly observe the activation of the nerve endings in skeletal muscles by both metabolites and mechanical stimulation. These images may allow us to determine the mechanisms for ?trigger points?, the pulsating nature of muscle ache, lymphatic disease associated with muscle fatigue and pain, and sympathetic activation of enhanced muscle pain. The specific aims of this proposal are: Aim 1: Define the different types of mechanosensitive, and metabosensitive sensory neurons innervating skeletal muscle based on their responses to muscle contraction. Aim 2: Determine if chemical mediators produced during muscle contraction are responsible for the potentiation seen among a subset of mechanosensitive muscle sensory neurons during muscle contraction. Aim 3: Determine if metaboreceptors and metabo-nociceptors also respond to mechanical forces generated during muscle contraction. Aim 4: Determine the location and structure of skeletal muscle sensory neurons signaling pain and fatigue via direct imaging of neuron terminals.