Exploratory studies of a rodent model for inhalant abuse

For simulation of inhalant abuse exposure conditions, male and female rats were exposed to high concentrations (10,000-30,000 ppm) toluene vapor until unconscious (8-12 min periods). Sex differences were observed in the mean times to onset of sleep during exposure; linear regression lines of min to sleep onset as a function of toluene/kg body wt had slopes of -0.7492 for males and -0.4515 for females. Animals were removed from the exposure chamber to clean air and both spontaneous horizontal locomotor activity (2/3 animals) and ppm toluene in exhaled air (1/3 animals) were monitored for the first hr post-exposure. Animals regained consciousness within the first 6-7 min and consistently displayed a characteristic pattern of locomotor activity: activity increased initially to 2-3 times baseline level (1 hr preceding exposure) and remained elevated for approximately 10 min; activity then decreased to baseline range for a time before a period of inactivity and/or sleep by 60 min post-exposure. Immediately after regaining consciousness the concentration of toluene exhaled decreased rapidly for the first 10 min, somewhat less rapidly for the next 10-20 min and levelled off at 100-200 ppm for the following 30-40 min. The occurrence and duration of hyperactivity coincided with the period of rapid elimination of unchanged toluene through the lungs.