Adolescent toluene inhalation in rats affects white matter maturation with the potential for recovery following abstinence

PLoS One. 2012;7(9):e44790. doi: 10.1371/journal.pone.0044790. Epub 2012 Sep 18.

Abstract

Inhalant misuse is common during adolescence, with ongoing chronic misuse associated with neurobiological and cognitive abnormalities. While human imaging studies consistently report white matter abnormalities among long-term inhalant users, longitudinal studies have been lacking with limited data available regarding the progressive nature of such abnormalities, including the potential for recovery following periods of sustained abstinence. We exposed adolescent male Wistar rats (postnatal day 27) to chronic intermittent inhaled toluene (3,000 ppm) for 1 hour/day, 3 times/week for 8 weeks to model abuse patterns observed in adolescent and young adult human users. This dosing regimen resulted in a significant retardation in weight gain during the exposure period (p<0.05). In parallel, we performed longitudinal magnetic resonance imaging (T₂-weighted) and diffusion tensor imaging prior to exposure, and after 4 and 8 weeks, to examine the integrity of white matter tracts, including the anterior commissure and corpus callosum. We also conducted imaging after 8 weeks of abstinence to assess for potential recovery. Chronic intermittent toluene exposure during adolescence and early adulthood resulted in white matter abnormalities, including a decrease in axial (p<0.05) and radial (p<0.05) diffusivity. These abnormalities appeared region-specific, occurring in the anterior commissure but not the corpus callosum and were not present until after at least 4 weeks of exposure. Toluene-induced effects on both body weight and white matter parameters recovered following abstinence. Behaviourally, we observed a progressive decrease in rearing activity following toluene exposure but no difference in motor function, suggesting cognitive function may be more sensitive to the effects of toluene. Furthermore, deficits in rearing were present by 4 weeks suggesting that toluene may affect behaviour prior to detectable white matter abnormalities. Consequently, exposure to inhalants that contain toluene during adolescence and early adulthood appear to differentially affect white matter maturation and behavioural outcomes, although recovery can occur following abstinence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / drug effects*
  • Brain / growth & development*
  • Brain / pathology
  • Brain / physiopathology
  • Diffusion Tensor Imaging
  • Inhalation*
  • Male
  • Motor Activity / drug effects
  • Rats
  • Rats, Wistar
  • Recovery of Function*
  • Rotarod Performance Test
  • Substance-Related Disorders / pathology
  • Substance-Related Disorders / physiopathology
  • Time Factors
  • Toluene / toxicity*

Substances

  • Toluene

Grants and funding

This research was supported by The National Health and Medical Research Council of Australia of which AJL is a Principal Fellow (1020737), the Australian Research Council (DP 110100379) of which JRD is a Future Fellow (100100235), The Lew Carty Foundation and the Alcohol and Health Research Grant Scheme. The authors also acknowledge the Victorian Government's Operational Infrastructure Support Scheme. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.