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Somatosensory System and Pain Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem lecture 5: Spinal signal processing 08-9 פיסיולוגיה מורחב 08-9 פיסיולוגיה מורחב
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stimulus response pain touch pain threshold stimulus pain threshold סף הכאב detection threshold
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touch pain innocuous noxious * * DRG classical labeled-line model AA Aδ+C
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WDR multireceptive some SG neurons are "nociceptive specific" X Rexed’s laminae
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touch pain innocuous noxious * * DRG classical labeled-line model AA Aδ+C
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Mismatch between stimulus and response stimulus הגירוי התגובה response כאב אלחוש hypoalgesia, analgesia
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Mismatch between stimulus and response stimulus הגירוי התגובה response כאב sensitisation ריגוש allodynia hyperalgesia
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inflammation דלקת burn infection abrasion allodynia + hyperalesia Inflammatory “triple response” rubor (red) calor (hot) tumor (swollen) dolor (pain)
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touch pain innocuous noxious * * DRG classical labeled-line model AA Aδ+C peripheral sensitization tactile allodynia is a challenge to the…
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דלקת sensitization of nociceptors "peripheral sensitization" "peripheral sensitization" ריגוש של קולטנים נוסיספטיביים
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“inflammatory soup” Inflammatory mediators מקדמי דלקת bradykinin histamine prostaglandins 5HT pH (protons) leukotrienes SP, CGRP “ quadruple response ”
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tactile allodynia in neuropathy
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classical labeled-line model touch pain innocuous noxious DRG AA C Tactile allodynia is not due to receptor sensitization rapid response latency heat, but no tactile sensitization tactile allodynia gone with A nerve block A nerve stimulation pain no flare
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Tactile allodynia is A pain response latency A nerve stimulation pain “secondary hyperalgesia” ischemic block mechanosensitization of C-noceptors ? peripheral neurography (human) intraneural microstimulation (human) Torebjork et al. 1992 high low electrical threshold optional
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“central sensitization” “specificity” labeled line WDR “gate control” regulated convergence descending control control by afferent input "A pain" touch pain touch or painrelativelyineffectivesynapse
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Some proposed mechanisms of central sensitization activation of NMDA-type glutamate receptors activation of spinal glia (microglia and astrocytes) which, in turn, release excitatory molecules (cytokines) loss of GABAergic interneurons background spontaneous drive minor depolarization sprouting of A afferents into Rexed lamina I increased intrinsic excitability of spinal WDR neurons
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“central sensitization” WDR “gate control” regulated convergence LTP, NMDA-R
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“Gate-control theory” Melzack & Wall 1965 presynaptic inhibition
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Somatosensory System and Pain Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem lecture 5: Spinal signal processing פיסיולוגיה מורחב
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P+P+ BT +
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gracely
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"relatively ineffective synapses" dynamic control of RF
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primary sensory neurons
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convergence divergence
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