MID-FREQUENCY HEARING-LOSS AND REDUCTION OF ACOUSTIC STARTLE RESPONDING IN RATS FOLLOWING TRICHLOROETHYLENE EXPOSURE

Modification of auditory evoked startle responding using prepulse inhibition was used to examine the effects of trichloroethylene (TCE) exposure on auditory thresholds. Rats were exposed by inhalation to 0, 1500, or 3000 ppm TCE for 18 hours per day, 5 days a week for 3 weeks. Auditory thresholds for 5 and 20 kHz tones were measured before exposure and at 1, 3, and 6 weeks postexposure. In addition, hearing thresholds for 5 and 35 kHz tones were examined at a 5-week postexposure time-point. Results indicated that hearing thresholds for 20 kHz but not for 5 or 35 kHz prepulses were significantly increased in rats exposed to 3000 ppm TCE. These findings demonstrate a selective hearing loss in the 20 kHz range by short-term, high-level TCE exposure. With respect to effects on startle responding per se, the present study also found that compared to controls, TCE-exposed rats failed to show an increase in baseline startle with repeated testing. This difference could not be attributed to differences in body weight and was persistent throughout the postexposure period.