08-9 Somatosensory System and Pain lecture 2: Stimulus transduction and encoding Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and
Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem "psychophysics" stimulus (physical units) neural representation (1,2,3,4) 4 perception
3 early processing 2 nerve transmission transduction & encoding 1 evolution planerian
bacteria, protozoa (tropism) separation of sensation and effect sensation response (effector organ) perception (information, emotional/affective vector)
regional functions of sensory neuron sensory 2 neuron dorsal root ganglion nerve
1 afferent sensory receptor ending Receptive field modality location/space
dynamics Sensory processing disaggregation reassembly binding perception action/ memory
location mosaic dermatome Transduction and encoding occur in the region of the sensory ending , exceptions: vision, olfaction audition
vestibular sense taste pain vibration touch itch proprioception
specialized sensory transduction cell transduction molecules anterograde axoplasmic transport How does transduction occur ?
mechanoreceptor channels mechanoreceptor channels mV 0 mV 60- generator potential
(generator depolarization) generator current mechano-gated channels thermal-gated channels ligand-gated receptors (some are channels)
receptor types/ sensory transduction: mechanical, thermal (<, >), chemical mechanical: receptor cells vs. C.elegans DEG/ENaC,
receptor drosophila TRPn, painless molecules vertebrates ? thermal: heat - TRPV1, TRPV2, TRPV3 (vanilloid, capsaicin)
cold - menthol-R TRPM8 chemical: capsaicin TRPV1 garlic, mustard TRPA1 histamine H1,H2 ASICs (acid sensing ion channels) BK-Rs (bradykinin)
PG-Rs (prostaglandins) etc. capsaicin receptor cloned (by D.Julius & M.Caterina et al. Nature 97) (cDNA from rodent DRG injected into HEK cells, screen for >Ca 2+ fluorescence on capsaicin application) vanilloid-R1 V1
by sequence homology very similar to drosophila transient receptor potential channel TRP TRPV1 TRP receptor familyTRPVs, TRPAs, TRPMs, TRPCs TRPV1: sensitive to capsaicin, proton heat, some endocannabinoid lipids ), pH
from stimulus to impulse train transduction spike encoding Pacinian corpuscle stimulus
encoding adaptation vs. habituation vibration, texture Dynamic response of sensory receptors frequency tuning curve
SA RA Pacinian corpuscle sensitivity Hz
300 100 0 dynamic range LTM vs. nociceptor "threshold"
encoding region saturation firing frequency Intensity scaling WDR
stimulus intensity firing frequency Intensity scaling LTM nociceptor
stimulus intensity firing frequency Intensity scaling LTM
nociceptor stimulus intensity from stimulus to impulse train 1. force transmission to sensory ending 2. transduction
3. spike encoding Stimulus transmission viscoelastic properties of skin Stimulus transmission viscoelastic properties of skin hair shaft
Stimulus transmission viscoelastic properties of skin hair shaft corpuscular endings muscle spindles blood flow (thermal) Stimulus transmission
viscoelastic properties of skin hair shaft corpuscular endings blood flow (thermal) muscle spindles muscle spindle
Variety of sensory endings (to code stimulus intensity, quality, dynamics) 1. force transmission to sensory ending 2. transduction 3. spike encoding RA
SA RA Variety of sensory endings A: LTMs: SA, RA, PC, hair A: warming, cooling, down hair, mechano-nociceptors C:
mechanical nociceptors mechano-heat nociceptors CMH polymodal nociceptors silent (sleeping) nociceptors Somatosensory System and Pain
lecture 2: Sensory transduction and encoding Prof. Marshall Devor, Ph.D. Dept. of Cell & Animal Biology and Center for Research on Pain Institute of Life Sciences Hebrew University of Jerusalem Somato-visceral sensation
Receptive Field tissue skin deep (musculoskeletal, visceral, brain) modality/ quality touch (static-dynamic (vibration, movement)) thermal chemical
sensory processing disaggregation signal processing reassembly quality binding intensity perception location
action/ memory dynamics
