Dimethylsulfoxide action on fast axoplasmic transport and ultrastructure of vagal axons.

The axonal microtubules (MT) are believed to be involved in fast axonal transport (FAXT). Dimethylsulfoxide (DMSO) has a strong stabilizing action on MT in vitro which may account for some of its reported biological effects. DMSO at concentrations of 5% disrupts the FAXT in a high percentage of axons emanating from the nodosum ganglion in the cat vagus nerve. Whereas 5% DMSO does not affect the FAXT in all axons, 10% DMSO blocks all the FAXT. The blockage is substantially, but not completely, reversed by washing the vagus for 2 h. DMSO at 2% caused no discernible change in either the FAXT or the axonal morphology, but some swelling of glial cells occurred. Ultrastructurally, 10% DMSO caused some axons to swell and others to shrink. The MT appeared normal and their total number per axon did not change. The spatial relationship of the axonal constituents is clearly altered by the DMSO and this may have contributed to the failure of the transport. It is suggested that the DMSO, through strengthening the forces involved in polymerization, renders them non-functional for FAXT.