Aluminum-induced decreases in choline acetyltransferase, tyrosine hydroxylase, and glutamate decarboxylase in selected regions of rabbit brain.

The neuropathological and neurochemical effects of intracisternally administered aluminum-powder suspensions were studied in adult rabbits. The right half of each brain was fixed for neuropathological examination, and neurotransmitter-synthesizing enzyme activities were measured in homogenates of structures dissected from the left half of each brain. The neuropathological changes associated with aluminum-induced encephalomyelopathy, including neurofibrillary degeneration, were observed in several regions of the central nervous system of the aluminum-treated rabbits. The striatum was consistently free of changes. Decreases in choline acetyltransferase and tyrosine hydroxylase activities of more than 30% were observed in the striatum of animals within 14-21 d and at longer times after aluminum injection. The decrease in striatal choline acetyltransferase activity appears to be unrelated to pathological changes in the striatal cholinergic neurons. The decrease in tyrosine hydroxylase activity in the striatum may be unrelated to neuropathological changes in dopaminergic cell bodies in the midbrain. Significant decreases in glutamate decarboxylase activity in the cerebellum may be related to cell losses in this region, whereas choline acetyltransferase activity deficits in the whole hippocampus remain unexplained.