Behavioural and ultrastructural studies of desmethylmisonidazole-induced neurotoxicity in mice.

The hypoxic cell radiosensitiser desmethylmisonidazole (DMM, Ro-05-9963) was administered orally to C3Hf female mice at three different dose levels (1.4, 1.6 and 1.8 mg g-1 day-1). Behavioural and morphological end-points were used to evaluate the neurotoxicity of this compound at these doses. The behavioural changes present at all three dose levels appeared when the total dose approached approximately 19 mg g-1. The behavioural changes initially appeared and developed to a severe state rapidly (24 to 48 h). A pattern of haemorrhagic necrosis was observed in the brain stem and cerebellum, but no pathology was observed in the cerebrum. Peripheral nerve degeneration was also evident and appeared concurrent with the central pathology. DMM appears to affect both the central and peripheral nervous systems at the same time at these dose levels. This is in some degree different from previous experience with misonidazole where peripheral damage distinctly precedes central effects. The development of the disorder appeared to be more rapid and severe when compared with earlier experience with misonidazole.