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A preclinical model of hyperalgesia following spinal stenosis/compression
Author(s) -
Vierck C.J.,
Baastrup C.,
MaerskMoller C.,
Roth M.,
Can R.L.,
Finnerup N.B.,
Yezierski R.P.
Publication year - 2015
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1002/ejp.640
Subject(s) - hyperalgesia , hypoalgesia , anesthesia , spinal cord , medicine , spinal canal stenosis , spinal canal , nociception , receptor , psychiatry
Background Identification of mechanisms for pain/hyperalgesia following spinal cord injury requires long‐term evaluation of individual subjects because of the variability in effect over time for humans. Methods Rats were trained on an operant escape task that determined their preference for occupancy of a brightly lit compartment versus a dark compartment with a floor preheated to 10, 32 or 44.5 ° C . Following determination of baseline preferences, the animals received extradural implantation of a small piece of polymer in the thoracic spinal canal. The polymer narrowed the spinal canal and compressed the spinal cord. Post‐operative tests of escape preference were conducted over 23 weeks (experiments 1 and 2) and 62 weeks (experiment 3), permitting statistical evaluation of individual effects. Results Spinal stenosis/compression produced hyperalgesia for cold and/or heat stimulation (17 animals; 77%), no post‐operative change in sensitivity (4 animals) or hypoalgesia for cold or heat (2 animals). When hyperalgesia occurred, it developed gradually over 4 months. Following removal of the polymer in experiment 3, heat sensitivity returned to baseline levels for four of four animals that had been hyperalgesic when the polymer was in place, but cold hyperalgesia was retained for four of five animals. Overall, post‐operative changes in cold and heat sensitivity were not strongly related, indicating that different mechanisms were responsible for enhanced sensitivity to 10 and 44.5 ° C . Conclusions Histology revealed that hyperalgesia occurred when there was: (1) damage to spinal white matter; or (2) cystic cavitation; or (3) compression and distortion of the spinal cord without an obvious loss of grey or white matter.