Nitrous Oxide Neurotoxicity Studies in Man and Rat

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Abstract
To assess the effects of chronic exposure to low levels of N2O on the neural function of man, the neurologic condition, motor and sensory nerve conduction and computerized tests of sensation in .apprx. 1/2 of the dentists in Rochester, Minnesota, were evaluated. Results of scored tests of neural function were not significantly different for dentists who used N2O extensively in their practices and dentists who did not. To assess the effects of chronic exposure to high levels of N2O on neural function and structure of experimental animals, groups of rats were exposed to 70% N2O in 30% O2 for 4 h, 5 days/wk, for 6 mo. Rats exposed to N2O and control rats showed no difference in well-being, in caudal nerve conduction, in axonal content and transport of acetylcholinesterase and dopamine-.beta.-hydroxylase or in number and size distribution and pathologic abnormality of teased myelinated fibers. A lack of peripheral nerve neurotoxicity of N2O in the rat is indicated, but the findings cannot be extended to men with heavy exposures.