Experimental spongy degeneration of the white matter induced by 6-aminonicotinamide intoxication.

Spongy state and degeneration of the white matter in the 6-aminonicotinamide intoxicated rats were studied neuropathologically and electromicroscopically. Young albino rats, four weeks of age, received 0.1% of 6-aminonicotinamide solution intraperitoneally as a single dose of 10 mg/Kg of body weight. Four hours after the administration, paralysis of the hind limbs occurred in the rats. Neuropathological investigations revealed a characteristic spongy and degenerative change of white matter as well as gray matter of the central nervous system. Corpus callosum, cerebellar cortex, and optic nerves showed edematous and spongy degeneration in the early stage of the experiment. Ultrastructural changes of myelin sheath were initially seen in the vicinity of severely damaged oligodendrocytes. The vacuoles in the myelin, i.e. intramyelinic vacuoles, were formed by splitting between the innermost myelin lamellae and axon. Axons remained usually unchanged in the early stage. The pathogenesis of ultrastructural changes of the white matter in the 6-aminonicotinamide intoxication was discussed.