Characterizing activity and muscle atrophy changes in rats with neuropathic pain: a pilot study.
The study of neuropathic pain has focused on changes within the nervous system, but little research has described systemic changes that may accompany neuropathic pain.


OBJECTIVE
As part of a larger project characterizing the metabolic, activity, and musculoskeletal changes associated with neuropathic pain, the objective of the current study was to characterize changes in spontaneous activity and skeletal muscle mass using an established animal model of neuropathic pain, the chronic constriction injury (CCI) model.


METHODS
Male Sprague-Dawley rats were used in this pre- and posttest quasi-experimental study. The experimental group (n = 13) received CCI surgery, while age- and weight-matched rats received sham surgery (SHAM; n = 5). Thermal testing verified the presence of neuropathic pain. Spontaneous cage activity was measured gravimetrically prior to and following CCI (n = 4). Animals were euthanized and skeletal muscle was dissected and weighed to determine muscle atrophy.


RESULTS
Shorter foot withdrawal latency of the ipsilateral hind limb confirmed the presence of thermal hyperalgesia in CCI rats, a sign of neuropathic pain. Weight increased in both CCI and SHAM rats. Spontaneous activity decreased following CCI ligation. Muscles of the ipsilateral hind limb weighed significantly less than contralateral hind limb muscles in CCI rats 2 and 6 weeks after surgery. In addition, CCI rats had smaller ipsilateral hind limb muscles than SHAM rats.


CONCLUSIONS
Neuropathic pain contributes to skeletal muscle atrophy and decreases in activity in rats.
1Department of Nursing, Calvin College, Grand Rapids, MI, USA.
Jesse R
JR
Moes
Janean E
JE
Holden
D000818:Animals; D008297:Male; D009133:Muscular Atrophy; D009437:Neuralgia / Q000503:physiopathology*; D010865:Pilot Projects; D051381:Rats; D017207:Rats, Sprague-Dawley
activity; muscle atrophy; neuropathic pain