Animals exposed to
allylnitrile develop permanent abnormalities in motor behaviour, similar to those caused by
3,3'-iminodipropionitrile (IDPN) and
crotononitrile. IDPN and
crotononitrile effects have been attributed to vestibular hair cell degeneration, but
allylnitrile has been suggested to modify behaviour through neuronal degeneration in the CNS. Adult male Long-Evans rats were exposed to
allylnitrile (0, 20, 40, 60 mg/kg per day, for 3 days) and the changes in rearing activity and rating scores in tests of vestibular function were assessed. Surface preparations of the vestibular sensory epithelia and the organ of Corti were observed for hair cell loss by scanning electron microscopy. Corneal transparency and concentrations in retina and olfactory bulbs of
glial fibrillary acidic protein (GFAP), a marker for reactive
gliosis, were also determined, as they are known targets of IDPN toxicity. In a dose-dependent manner,
allylnitrile caused
corneal opacity and
gliosis in the retina and olfactory bulbs, decreased rearing activity and increased the rating scores in tests of vestibular dysfunction, and induced hair cell loss in both the vestibular sensory epithelia and the organ of Corti. The behavioural deficits correlated well with the loss of vestibular hair cells. We conclude that
allylnitrile causes permanent modifications in behaviour by loss of vestibular function as IDPN and
crotononitrile do and that all these chemicals share other toxic targets, such as the cornea, the retina, and the olfactory system. Data reported here and elsewhere indicate that a number of
nitriles show similar neurotoxic properties.