title: Effects of different dosage of dexamethasone on behavioral, electrophysiological, and histomorphological recovery in a chronic sciatic nerve compression model.
abstract: OBJECTIVE
  To investigate the effects of different doses of topical dexamethasone (Dex) on sciatic nerves with simulated compressive neuropathy.
  
  
  METHODS
  Thirty-two Wistar rats were divided into four groups of 8: Sham group: no compression of the sciatic nerve + no treatment; Saline: chronic compression of the left sciatic nerve for 4 weeks + saline; 0.8% Dex: chronic compression + 0.8 mg of Dex; 3.2% Dex: chronic compression + 3.2 mg of Dex. Two sponge strips soaked with saline or Dex were placed under and over the nerve for 30 min in both Dex groups. Mixed-nerve-elicited somatosensory evoked potentials (M-SSEPs) and compound muscle action potentials (CMAPs) were measured to verify the compressive neuropathy in post-treatment follow-up. Behavioral observations of thermal hyperalgesia tests were quantified before electrophysiological examinations. Treated and contralateral nerves were harvested for histomorphological analysis.
  
  
  RESULTS
  M-SSEP and CMAP amplitudes significantly decreased and latencies were significantly prolonged on postcompression thermal hyperalgesia tests. Rats in both Dex groups showed significant improvement in both sensory and motor conductive values and in neurological function, as well as increased mean myelin diameter on the final histomorphological examination. For rats in the saline group, these parameters showed incomplete recovery compared with the Sham group and the precompression baseline. Moreover, the changes after Dex treatment were not dose-dependent.
  
  
  CONCLUSIONS
  Topical Dex reversed electrophysiological, behavioral, and structural changes in chronically compressed sciatic nerves. Differences between the beneficial effects of high-dose and low-dose Dex were nonsignificant.
authors.affiliation: Department of Orthopedics, Chi-Mei Medical Center, Tainan, Taiwan.
authors.forename: Ping-Hui
authors.initials: PH
authors.lastname: Wang
authors.forename: Ching-Lin
authors.initials: CL
authors.lastname: Tsai
authors.forename: Kuo-Chen
authors.initials: KC
authors.lastname: Wu
authors.forename: Chung-Jung
authors.initials: CJ
authors.lastname: Shao
authors.forename: Li-Chieh
authors.initials: LC
authors.lastname: Kuo
authors.forename: I-Ming
authors.initials: IM
authors.lastname: Jou
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000287:Administration, Topical; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage*; D003907:Dexamethasone / Q000008:administration & dosage*; D004195:Disease Models, Animal; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D008297:Male; D009408:Nerve Compression Syndromes / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve; D020426:Sciatic Neuropathy / Q000188:drug therapy*
chemical_list: D000893:Anti-Inflammatory Agents; D003907:Dexamethasone
keywords: Dexamethasone; Evoked Potentials; Local Application; Rat; Sciatic Nerve