Decreases in brain glial fibrillary acidic protein (GFAP) are associated with increased serum corticosterone following inhalation exposure to toluene.

Toluene and other neurotoxicants can cause both increases and decreases in the concentration of GFAP in the brain. While increased GFAP concentration is widely regarded as evidence for reactive gliosis, toxicant-induced decreases in GFAP have received less attention. In order to identify conditions under which inhalation exposure to toluene results in decreased GFAP concentration, rats were subjected to repeated inhalation of toluene for up to 7 days. Adult male F344 rats received inhalation exposure to air or to 1000 ppm toluene, 6 hr/day, for 3 or 7 days. This toluene exposure replicated the previously-observed decreases in GFAP in the thalamus. Serum Corticosterone was significantly elevated in the same rats that exhibited decreases in brain GFAP concentration. These results show that decreases in brain GFAP might be a consequence of disruption of the hypothalamic-pituitary-adrenal axis and/or hormonal homeostasis. Changes in GFAP and in Cort were not accompanied by a change in body weight. More research is needed to firmly establish cause and effect between increased serum glucocorticoid levels and GFAP decreases following toluene inhalation and to determine whether these decreases indicate toxicity or adaptive changes.