Evoked potential changes from 13 weeks of simulated toluene abuse in rats

Fischer 344 rats were exposed to 8000 ppm toluene vapor in an 'abuse' paradigm for 13 weeks to develop an animal model for 'solvent neurotoxicity.' Exposures to toluene were multiple and short (15 to 35 min), adjusted according to tolerance. Although body weight was reduced 23% from controls, the toluene-exposed rats appeared healthy. Evoked potentials taken postexposure were, however, mildly to severely affected. Flash-evoked potentials were slow and topographically disorganized; 10 kHz tone-pip auditory brainstem responses (ABRs) had severe loss of power and loss of detail. Click and 30 kHz ABRs, somatosensory-evoked potentials, and caudal nerve action potentials were less affected. No neuropathologic changes were detected by light microscopy (perfusion fixation, special stains). Thus, postexposure multimodal functional effects were readily detected after subchronic, severe episodic exposures to toluene.