Decreased sensitivity in adolescent vs. adult rats to the locomotor activating effects of toluene

Volatile organic solvent (inhalant) abuse continues to be a major health concern throughout the world. Of particular concern is the abuse of inhalants by adolescents because of its toxicity and link to illicit drug use. Toluene, which is found in many products such as glues and household cleaners, is among the most commonly abused organic solvents. While studies have assessed outcomes of exposure to inhalants in adult male animals, there is little research on the neurobehavioral effects of inhalants in female or younger animals. In attempt to address these shortcomings, we exposed male and female Long-Evans rats to 20 min of 0, 2000, 4000, or 8000 parts per million (ppm) inhaled toluene for 10 days in rats aged postnatal (PN) day 28–39 (adolescent), PN44–PN55, or >PN70 (adult). Animals were observed individually in 29-l transparent glass cylindrical jars equipped with standard photocells that were used to measure locomotor activity. Toluene significantly increased activity as compared to air exposure in all groups of male and female rats with the magnitude of locomotor stimulation produced by 4000 ppm toluene being significantly greater for female adults than during any age of adolescence. The results demonstrate that exposure to abuse patterns of high concentrations of toluene through inhalation can alter spontaneous locomotor behavior in rats and that the expression of these effects appears to depend upon the postnatal age of testing and sex of the animal.