The
anticonvulsant drug gabapentin has been demonstrated to alleviate symptoms of
painful diabetic neuropathy as well as other types of
neuropathic pain. The aim of the present study was to investigate the effect of
gabapentin in a recently developed mouse model of
peripheral neuropathy. This model is based on a photochemical ischemic lesion of the sciatic nerve generated by
laser-induced activation of the photosensitizing
dye erythrosin B. Following
laser irradiation of the sciatic nerve for 2, 5, or 10 min,
tactile allodynia was observed during at least 3 weeks. The degree of
allodynia was most marked following 10 min of irradiation. Subcutaneous administration of
gabapentin [175-300 micromol/kg ( approximately 30-51 mg/kg), cumulative doses, at 1-h intervals] significantly reversed
tactile allodynia induced by 10-min
laser irradiation. The maximal dose of
gabapentin increased the withdrawal threshold from approximately 0.55 to approximately 1.85 g (i.e., about 77% of the threshold in normal animals, approximately 2.4 g).
Gabapentin did not affect the tactile withdrawal threshold in intact animals. A dose of
gabapentin (100 micromol/kg, sc) that had no effect on
allodynia was found to significantly reduce the
pain behavior during phase 2 of the
formalin test. The present study demonstrates that systemic administration of
gabapentin suppresses both
allodynia induced by an ischemic lesion of the sciatic nerve and
pain behavior in the
formalin test.