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?
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Type I afferents, large myelinated axons,95% of nerve, carry sound.
Type II afferents, small axons, 5% of nerve unmyelinated, carry ???.
Type I neuron:95% of afferentsContacts single IHC
Type II neuron:5% of afferentsContact many OHCs
Berglund and Ryugo ,1987
Cat Weisz6
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 skinto study transduction of pain
Patapoutian et al. 2003,
The Hopkins Pain Workgroup
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