Vestibulo-ocular disturbances in rats exposed to organic solvents.

The influence of different kinds of industrial solvents on the vestibular function of rats has been studied by recording nystagmus, induced by accelerated rotation. The effect was related to the blood levels of the solvents. One group of solvents, including halogenated saturated hydrocarbons like dichloromethane, caused depression of the vestibulo-oculomotor reflex (VOR). Another group, including benzene compounds like xylene, toluene, styrene and cumene and halogenated unsaturated hydrocarbons like trichloroethylene caused an excitation of the VOR. The most striking chemical similarity between the different solvents in the last group is the occurrence of double-bonds. If the animals were exposed simultaneously to solvents from both groups the excitatory effect prevailed and was even potentiated. It is suggested that solvents cause depression or excitation of the VOR by interaction with central pathways in the reticular formation and the cerebellum.