Effects of repeated inhalation of toluene on ionotropic GABAA and glutamate receptor subunit levels in rat brain

Toluene is a commonly abused solvent found in many industrial and commercial products. The neurobiological effects of toluene remain unclear, but many of them, like those of ethanol, may be mediated by γ-aminobutyric acid (GABA) and glutamate receptors. Chronic ethanol administration has been shown to alter levels of specific subunits for GABA type A (GABAA), N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. However, little is known about the effects of toluene on subunit levels of these receptors. To examine this, rats were exposed to toluene vapors (8000 ppm) or air for 10 days (30 min/day), and afterwards GABAA α1, NR1 and NR2B (NMDA) and GluR1 and GluR2/3 (AMPA) receptor subunit levels were determined in discrete brain regions of these animals by Western blotting. Toluene increased GABAA α1, NR1, NR2B and GluR2/3 subunits in the medial prefrontal cortex and decreased GABAA α1 and NR1 subunits in the substantia nigra compacta. Toluene inhalation produced modest increases in GABAA α1 subunits in the striatum, as well as slight decreases in this subunit in the ventral tegmental area. NR2B subunit levels were also slightly increased within the nucleus accumbens by toluene. These studies show that toluene differentially alters the levels of specific GABAergic and glutamatergic receptor subunits in a regionally selective manner.