Transcript PowerPoint

The Hopkins Pain Workgroup
“Seeing Pain More Clearly”
Optogentic and electrophysiological assay of pain fibers in skin
(mice): Michael Caterina, Xinzhong Dong ,Yun Guan, Paul Fuchs
Genetically-visualized pain fibers (mice): Xinzhong Dong, Yun
Guan, Srinivasa Raja
Functional and molecular characterization of pain fibers in
nonhuman primates: Xinzhong Dong, Joseph Mankowski, Matthias
Ringkamp
Functional and molecular characterization of pain fibers in
patients with painful peripheral neuropathy: Michael Caterina,
Michael Polydefkis
Pain…
Pain in the (r)Ear
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Innervation of the cochlea:
analogous to skin?
Type I afferents, large myelinated axons,
95% of nerve, carry sound.
Type II afferents, small axons, 5% of
nerve unmyelinated, carry ???.
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Type I neuron:
95% of afferents
Contacts single IHC
Type II neuron:
5% of afferents
Contact many OHCs
Cat Weisz
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Berglund and Ryugo ,1987
Progress to date
• Type II afferents poorly driven by OHCs – so
would respond only to (very) LOUD sound
• But, type II afferents also excited by ATP
(involved in pain sensation in skin). ATP is
released during acoustic trauma.
• Do type II afferents carry ‘ear pain’? The jury
is still out.
Hyperacusis, tinnitus:
altered afferent balance?
Acoustic
trauma
Type II
afferents
remain
Adapt fiber recording methods to excised skin
to study transduction of pain
Patapoutian et al. 2003,
The Hopkins Pain Workgroup