[Abstract Title]. - Society for Neuroscience

268. Neuropathic Pain Mechanisms: Ion Channels
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 268.10/GG7
Topic: D.08.k. Inflammatory pain
Support: Supported by Wellcome UK grant to SNL & GR
Title: The distribution of the two-pore domain K + (K2P) channel TREK2 (KCNK10) in dorsal
root ganglion (DRG) neurons after axotomy or skin inflammation
Authors: *G. REID 1 , B. MARSH 2 , R. S. SHAH 2 , K. MORGAN 2 , R. PAREKH 2 , C. BERRY 2 ,
B. CARRUTHERS 2 , L. DJOUHRI 3,2 , S. N. LAWSON 2 ;
1 Dept of Physiol., Univ. Col. Cork, Cork, Ireland; 2 Dept. of Physiol. and Pharmacol., Univ. of
Bristol, Bristol, United Kingdom; 3 Dept. of Pharmacol. & Therapeut., Univ. of Liverpool,
Liverpool, United Kingdom
Abstract: Changes in membrane potential (Em) in DRG neurons may influence firing frequency
in chronic pain states. Spontaneous firing occurs in some A-fibre neurons after axotomy, and in
C and Aδ neurons during cutaneous inflammation (1).
Altered expression of background (K2P) potassium channels could influence resting excitability
and thus spontaneous firing. We have examined DRG expression of the K2P channel TREK2
(KCNK10) in chronic pain models using both real time RT-PCR and ABC
immunocytochemistry. We examined ipsilateral and contralateral L5 DRGs 1 week after L5
spinal nerve axotomy (SNA; neuropathic pain model), and L5/L4 DRGs 1 and 4 days after
intradermal injection of complete Freund‟s adjuvant in one hindpaw (CFA; chronic
inflammatory pain model). For PCR, single DRGs were measured with GAPDH as reference
gene. For immunocytochemistry, cytoplasmic staining of neuronal profiles containing nuclear
sections was measured within small circles placed in the edge, mid, and juxta-nuclear regions of
the cytoplasm.
TREK2 mRNA expression did not differ between ipsi- and contralateral DRGs in any group, so
ipsi- and contra-lateral data sets were combined. There was no detectable change in CFA day 1
(n=4) or CFA day 4 (n=4) DRGs from normal (n=6). Axotomised DRGs showed higher
expression than combined CFA DRGs (p500κm 2 ) was decreased throughout the cytoplasm in all treatments. In small
(≤500κm 2 ) neurons staining was unchanged 1 day after CFA but significantly reduced
throughout the cytoplasm 4 days after CFA. After axotomy, juxta-nuclear staining increased but
edge staining decreased.