Toxicity and cryoprotection by dimethyl sulfoxide and by glycerol in isolated frog sciatic nerves

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Isolated frog sciatic nerves with or without intact perineural sheaths were exposed to 5, 10, or 15% dimethyl sulfoxide (DMSO) or glycerol in Ringer's solution for 15 min. Then either the nerves were allowed to recover in normal Ringer's solution, or they were frozen at −10°C in the presence or absence of these protective agents and then allowed to recover in normal Ringer's solution. By this procedure the toxicity of the protective agents was distinguished from freeze-thaw damage. The following electrical parameters were measured before treatment and after 30 and 60 min of recovery in Ringer's solution: 1) conduction velocity, 2) action potential, and 3) absolute refractory period. The results may be summarized as follows. 1) Neither DMSO nor glycerol severely damaged the nerves, but the effect of each was different in some of the parameters measured. In general, a) the effects of DMSO were less dramatic and more reversible than the effects of glycerol; b) except for the conduction velocity, the effects of DMSO appeared to be independent of the presence of absence of the nerve sheath, whereas the changes wrought by glycerol were greater in desheathed nerves. 2) All nerves frozen without protective agents no longer responded to external stimuli. 3) Glycerol did not protect nerves with or without intact perineural sheaths from freeze-thaw damage. 4) DMSO did not protect nerves with intact sheaths but did protect desheathed nerves from freeze-thaw damage. 5) The cryoprotection by DMSO was not complete; i.e., freeze-thawed nerves did not recover to the same extent as nerves only exposed to DMSO.