Effects of hexane on the brainstem auditory response and caudal nerve action potential.

In a study on the neurotoxicity of abused inhalants, male Fischer rats were exposed by inhalation to several concentrations of hexane, administered continuously or intermittently. The fifth component of the brainstem auditory-evoked response (BAER) increased in latency and decreased in amplitude in rats exposed to 1,000 ppm of hexane 24 hours per day, 5 days per week, for 11 weeks. The first component of the BAER was only slightly affected, indicating that the increased latency of the fifth component reflected a brainstem dysfunction. Latency returned to normal within 5 weeks after termination of exposures, but amplitude did not. Latency of the compound action potential of the ventral caudal nerve of the tail of these rats was also increased, and this effect was still present 22 weeks after termination of the exposure. Other rats were not as severely affected by repeated, brief (10 minutes) exposures to 24,000 or 48,000 ppm hexane 6 or 12 times per day; only the amplitude of the fifth BAER component was affected by the 48,000-ppm exposure.