Fos induction in the brain of mice exhibiting behavioral abnormalities following administration of allylnitrile or crotononitrile

Allylnitrile and crotononitrile induce behavioral abnormalities in mice. To explore the possible involvement of the vestibular system in these behavioral abnormalities, the expression of Fos protein, used as an indicator of neuronal activity, was examined within various brain structures in allylnitrile-, crotononitrile- and vehicle-treated mice. In each nitrile-treated mouse, Fos expression was observed in brain structures, which were divided into two groups. The structures in group 1 showed Fos expression between 1.5 h and 2 days postdosings, and in those in group 2 expression remained for up to 30 days postdosing. As most of these structures, especially in group 2, were identical to some Fos-positive structures observed after unilabyrinthectomy, the present results indicate that each nitrile induces Fos expression by causing a change in the peripheral vestibular system, resulting in behavioral abnormalities.