Biochemical changes in different brain areas after toluene inhalation.
Exposure to toluene causes both reversible and irreversible changes in the central nervous system. The effects of toluene inhalation on some specific enzymes and glutamate and GABA receptor binding in defined parts of the rat brain were studied following several exposure schemes. The activities of the transmitter synthesizing enzymes glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT) and aromatic amino-acid decarboxylase (AAD) were used as markers for permanent loss of neuronal activity. Catecholaminergic neurons showed a 50% reduction in the brain stem after 4 weeks exposure to 250 and 1000 ppm toluene. Following 500 ppm of toluene, 16 h/day for 3 months, a general increase in the activities was seen. This is most probably due to a reduction in total protein content, to which the activities were related. The neurotransmitters glutamate and GABA had their specific receptor binding increased in most of the brain areas studied, but decreased in some areas. The glial enzyme, glutamine synthetase, had its activity increased in the cerebellar hemisphere following 4 weeks exposure to 1000 ppm. This suggests that glial cells in the area may have proliferated, a frequent phenomenon following CNS damage.
Bjornaes
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Norwegian Defence Research Establishment, Department of Environmental Toxicology, Kjeller.
Naalsund
L U
LU
D000280:Administration, Inhalation; D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000032:analysis; D001923:Brain Chemistry / Q000187:drug effects*; D001933:Brain Stem / Q000187:drug effects; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000378:metabolism; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000378:metabolism; D014050:Toluene / Q000633:toxicity*
D011963:Receptors, GABA-A; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D014050:Toluene; D001142:Aromatic-L-Amino-Acid Decarboxylases