[Behavioral changes in the rats following inhalation of mercury vapor (author's transl)]

The present study was designed to determine critical brain mercury concentrations associated with specific behavioral changes during exposure to mercury vapor. Rats exposed to 3 mg of Hg/m3 for 3 hours, 5 days per week, for 15-42 weeks, showed a decline in conditioned avoidance response. The latency of escape response also increased in pole climb shock escape. The time to the onset of effects varied from 12 to 39 weeks among 14 rats exposed to mercury. All rats recovered to preexposure baseline within 12 weeks after the termination of exposure. A significantly poor behavioral performance was noticed in rats with brain mercury concentration of approximately 20 microgram Hg/g. Behavioral recovery was seen when the mercury concentrations decreased to 10 microgram Hg/g brain tissue. These results suggest that the critical concentration of inorganic mercury in the brain associated with behavioral changes in the rat ranges about 10 ppm to 20 ppm. In spite of the high concentration of mercury, the nervous tissues of rats in this experiment with mercury vapor intoxication were normal.