Single toluene exposure and changes of response latency in shock avoidance performance.

The behavioral effects of a single exposure to toluene were investigated using shock avoidance performance. Rats were exposed to 2000, 4000, 6000, and 8000 ppm toluene vapor for 4 hr after they acquired shock avoidance learning. Then the effects of toluene on avoidance performance, locomotor activity, and response latencies (RLs) were simultaneously examined for 3 days. Shock avoidance responses were significantly decreased at concentrations of 4000, 6000, and 8000 ppm, but recovered 3-6 hr after the cessation of exposure. The 2000 ppm exposure had no effect on these responses. Locomotor activity was transiently increased at concentrations of 2000 ppm and 4000 ppm, but recovered after 6 hr. Both 6000 ppm and 8000 ppm exposure at first decreased locomotor activity but later increased it. There were biphasic effects, inhibition and excitation, on locomotor activity, and it took 1 day to recover from them. Response latencies were shortened at concentrations of 2000, 6000, and 8000 ppm. That was due to hyperactivity. However, 4000 ppm toluene exposure induced the prolongation of RLs, although ataxia or narcosis were not observed. It was suggested that certain higher nervous functions in the central nervous system (CNS) which controlled timing behavior might be confused.