Effect of the hydroxyl radical scavenger, dimethylthiourea, on peripheral nerve tissue perfusion, conduction velocity and nociception in experimental diabetes.
OBJECTIVE
Increased oxidative stress has been linked to diabetic neurovascular complications, which are reduced by antioxidants. Our aim was to assess the contribution of hydroxyl radicals to early neuropathic changes by examining the effects of treatment with the specific scavenger, dimethylthiourea, on nerve function and neural tissue blood flow in diabetic rats.


METHODS
Diabetes was induced by streptozotocin. Measurements comprised sciatic nerve motor and saphenous nerve sensory conduction velocity. Responses to noxious mechanical and thermal stimuli were estimated by Randall-Sellito and Hargreaves tests respectively. Sciatic nerve and superior cervical ganglion blood flow were measured by hydrogen clearance microelectrode polarography.


RESULTS
Eight weeks of diabetes reduced motor and sensory conduction velocity by 19.9% and 15.7% respectively, and these were completely corrected by 2 weeks of dimethylthiourea treatment. The ED50 for motor conduction was 9 mg kg(-1) x day(-1). Mechanical and thermal nociceptive sensitivities were 18.9% and 25.0% increased by diabetes, respectively, indicating hyperalgesia which was 70% reduced by dimethylthiourea. Sciatic endoneurial and superior cervical ganglion blood flows were 51.2% and 52.4% reduced by diabetes and there was an approximately 80% improvement with treatment.


CONCLUSIONS
Hydroxyl radicals seem to make a major contribution to neuropathy and vasculopathy in diabetic rats. Treatment with the hydroxyl scavenger, dimethylthiourea, was highly effective. The data suggest that the development of potent hydroxyl radical scavengers suitable for use in man could markedly enhance the potential therapeutic value of an antioxidant approach to the treatment of diabetic neuropathy and vascular disease.
Cameron
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Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Scotland, UK. n.e.cameron@abdn.ac.uk
Tuck
Z
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McCabe
L
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Cotter
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MA
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D016166:Free Radical Scavengers; D017665:Hydroxyl Radical / Q000378:metabolism*; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009431:Neural Conduction / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D018384:Oxidative Stress; D010525:Peripheral Nerves / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000098:blood supply / Q000503:physiopathology; D017783:Superior Cervical Ganglion / Q000098:blood supply / Q000503:physiopathology; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology*
D016166:Free Radical Scavengers; D017665:Hydroxyl Radical; C038983:1,3-dimethylthiourea; D013890:Thiourea