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Behavioral changes following 4-week inhalation exposure to pseudocumene (1,2,4-trimethylbenzene) in the rat
S Gralewicz1, D Wiaderna, T Tomas
1Department of Toxicity Evaluation, Nofer Institute of Occupational Medicine, Lodź, Poland. impx@plunlo51.bitnet
Abstract:
Pseudocumene (1,2,4-trimethylbenzene, TMB) is a component of several solvent mixtures. During recent studies on rats we investigated the effect of a 4-week (6 h/day, 5 days/week) inhalation exposure to TMB at concentrations of 0, 25, 100, or 250 ppm on radial maze performance, open field activity, passive avoidance, active two-way avoidance, and shock-induced changes in the pain sensitivity reflecting the magnitude of the shock-induced fear response (hot plate test). The tests were performed between days 14 and 54 after the last exposure. The radial maze performance was not disturbed in any dose group. During testing in the open field grooming was significantly increased in rats exposed to 100 ppm TMB. In rats exposed to 100 and 250 ppm TNB, a foot shock applied after stepping off an elevated platform (a safe area) resulted in a significantly smaller increase in the step-down latency (i.e., passive avoidance, on days 3 and 7 after the foot shock) than in sham-exposed animals. Learning of a two-way active avoidance was slightly retarded in rats exposed to 250 ppm of TMB. Results of the hot plate test revealed no differences between groups in the paw sensitivity to heat (54.5 degrees C) before a 2-min intermittent food shock, but in rats exposed to 100 and 250 ppm of TMB the foot shock-induced fear response persisted apparently longer. These results suggest that inhalation exposure to TMB may lead to long-lasting disturbances in CNS functions.
Insights
Inhalation exposure to pseudocumene (1,2,4-trimethylbenzene, TMB) caused long-lasting central nervous system disturbances in rats, affecting fear responses and learning. Radial maze performance remained unaffected by TMB exposure.
Area of Science:
- Neuroscience
- Toxicology
- Environmental Health
Background:
- Pseudocumene (1,2,4-trimethylbenzene, TMB) is a common solvent mixture component.
- Understanding TMB's neurotoxic potential is crucial for occupational and environmental safety.
Purpose of the Study:
- To investigate the long-term effects of TMB inhalation exposure on rat central nervous system (CNS) functions.
- To assess behavioral and sensory responses following sub-chronic TMB exposure.
Main Methods:
- Rats were exposed to TMB (0, 25, 100, 250 ppm) via inhalation for 4 weeks (6 h/day, 5 days/week).
- Behavioral tests included radial maze, open field, passive avoidance, and active two-way avoidance.
- Pain sensitivity and fear responses were evaluated using the hot plate test and step-down latency.
Main Results:
- TMB exposure did not impair radial maze performance.
- Increased grooming was observed in the 100 ppm TMB group in the open field test.
- Passive avoidance learning was impaired, and fear responses persisted longer in rats exposed to 100 and 250 ppm TMB.
- Active avoidance learning was slightly retarded in the 250 ppm TMB group.
Conclusions:
- Sub-chronic inhalation of TMB can induce persistent neurobehavioral changes in rats.
- TMB exposure appears to affect fear-related behaviors and learning processes.
- These findings highlight potential long-lasting CNS risks associated with pseudocumene exposure.