Abstract
In an attempt to understand mechanisms underlying peripheral sensitization of primary afferent fibers, we investigated the presence of the tetrodotoxin-resistant Na+ channel subunits Nav1.8 (SNS) and Nav1.9 (SNS2) on axons in digital nerves of normal and inflamed rat hindpaws. In normal animals, 14.3% of the unmyelinated and 10.7% of the myelinated axons labeled for the Nav1.8 subunit. These percentages significantly increased in 48 h inflamed animals to 22.0% (1.5-fold increase) and 57.5% (6-fold increase) for unmyelinated and myelinated axons, respectively. In normal animals, Nav1.9 labeled 9.9% of the unmyelinated and 2.1% of the myelinated axons and following inflammation, the proportion of Nav1.9-labeled unmyelinated axons significantly decreased to 3.0% with no change in the proportion of labeled myelinated axons. These data indicate that Nav1.8 and Nav1.9 subunits are transported to the periphery in normal animals and are differentially regulated during inflammation. The massive increase in Nav1.8 expression in myelinated axons suggests that these may contribute to peripheral sensitization and inflammatory hyperalgesia.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Freund's Adjuvant
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Ganglia, Spinal / metabolism
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Ganglia, Spinal / physiopathology
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Ganglia, Spinal / ultrastructure
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Hyperalgesia / chemically induced
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Hyperalgesia / metabolism*
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Hyperalgesia / physiopathology
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Immunohistochemistry
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Inflammation / chemically induced
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Inflammation / metabolism*
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Inflammation / physiopathology
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Microscopy, Electron
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NAV1.8 Voltage-Gated Sodium Channel
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NAV1.9 Voltage-Gated Sodium Channel
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Nerve Fibers, Myelinated / metabolism
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Nerve Fibers, Myelinated / ultrastructure
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Nerve Fibers, Unmyelinated / metabolism
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Nerve Fibers, Unmyelinated / ultrastructure
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Nerve Tissue Proteins / antagonists & inhibitors
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Nerve Tissue Proteins / metabolism*
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Neurons, Afferent / metabolism*
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Neurons, Afferent / ultrastructure
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Neuropeptides / antagonists & inhibitors
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Neuropeptides / metabolism*
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Nociceptors / metabolism*
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Nociceptors / physiopathology
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Rats
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Sodium Channel Blockers / pharmacology
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Sodium Channels / metabolism*
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Tetrodotoxin / pharmacology
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Up-Regulation / physiology
Substances
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NAV1.8 Voltage-Gated Sodium Channel
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NAV1.9 Voltage-Gated Sodium Channel
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Nerve Tissue Proteins
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Neuropeptides
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Scn10a protein, rat
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Scn11a protein, rat
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Sodium Channel Blockers
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Sodium Channels
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Tetrodotoxin
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Freund's Adjuvant