Tolerance during inhalation of organic solvents

Characterization of the effects of inhaled perchloroethylene on sustained attention in rats performing a visual signal detection task

The aliphatic hydrocarbon perchloroethylene (PCE) has been associated with neurobehavioral dysfunction including reduced attention in humans. The current study sought to assess the effects of inhaled PCE on sustained attention in rats performing a visual signal detection task (SDT). Due to its similarities in physiological effect to toluene and trichloroethylene (TCE), two other commonly used volatile organic compounds (VOCs) known to reduce attention in rats, we hypothesized (1) that acute inhalation of PCE (0, 500, 1000, 1500 ppm) would disrupt performance of the SDT in rats; (2) that impaired accuracy would result from changes in attention to the visual signal; and (3) that these acute effects would diminish upon repetition of exposure. PCE impaired performance of the sustained attention task as evidenced by reduced accuracy [P(correct): 500 to 1500 ppm], elevated response time [RT: 1000 and 1500 ppm] and reduced number of trials completed [1500 ppm]. These effects were concentration-related and either increased (RT and trial completions) or remained constant [P(correct)] across the 60-min test session. The PCE-induced reduction in accuracy was primarily due to an increase in false alarms, a pattern consistent with reduced attention to the signal. A repeat of the exposures resulted in smaller effects on these performance measures. Thus, like toluene and TCE, inhaled PCE acutely impaired sustained attention in rats, and its potency weakened upon repetition of the exposure.

Effects of inhaled 1,1,1-trichloroethane on locomotor activity in mice

To quantify the motoric effects of an abused solvent, photocells were added to two exposure systems. The first system utilized a static exposure chamber that recirculated vapor-laden air. A second dynamic system allowed for removal of waste gases with replenishment of fresh air combined with test vapors. In the present studies, male mice were examined for effects on locomotor activity following 30-min inhalation exposures to several concentrations of 1,1,1-trichloroethane (TCE), a widely used and abused solvent. TCE produced significant increases in locomotor activity at intermediate concentrations. Minimally effective concentrations for activity-increasing effects in the dynamic and static systems were 1,250 ppm and 2,500 ppm, respectively. At higher concentrations, motor activity was decreased with the highest dynamic system concentration (10,000 ppm), resulting in 26% of baseline control values. Biphasic, motor activity increasing and decreasing effects of TCE as a function of exposure concentration may reflect the CNS-depressant drug-like effects of abused solvents.