Effects of different dosage of dexamethasone on behavioral, electrophysiological, and histomorphological recovery in a chronic sciatic nerve compression model.
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.
['Wang|Ping-Hui|PH|', 'Tsai|Ching-Lin|CL|', 'Wu|Kuo-Chen|KC|', 'Shao|Chung-Jung|CJ|', 'Kuo|Li-Chieh|LC|', 'Jou|I-Ming|IM|']
D000200:Action Potentials D000287:Administration, Topical D000818:Animals D000893:Anti-Inflammatory Agents D003907:Dexamethasone D004195:Disease Models, Animal D005073:Evoked Potentials, Somatosensory D008297:Male D009408:Nerve Compression Syndromes D051381:Rats D017208:Rats, Wistar D012584:Sciatic Nerve D020426:Sciatic Neuropathy
Dexamethasone Sciatic Nerve Rat Evoked Potentials Local Application