Huntington's Chorea: Changes in Neurotransmitter Receptors in the Brain

Neurotransmitter-receptor binding sites for apparent muscarinic cholinergic, β-adrenergic, γ-aminobutyric acid and serotonin receptors were measured in the caudate nucleus and frontal cerebral cortex from post-mortem brains of 16 patients with Huntington's chorea and 16 controls. In addition, the samples were assayed for the γ-aminobutyric-acid-synthesizing enzyme, glutamic acid decarboxylase, and for the acetylcholine-synthesizing enzyme, choline acetyltransferase. In the caudate nucleus of choreic brain, both enzyme activities were markedly lower, with significant decreases in muscarinic cholinergic and serotonin receptor binding, whereas enzyme activities and receptor binding were unchanged in the cerebral cortex. By contrast, γ-aminobutyric acid and β-adrenergic receptor binding were not significantly different in choreic and control caudate nucleus or cortex, suggesting that, despite the loss of γ-aminobutyric-acid-synthesizing ability in the corpus striatum, γ-aminobutyric acid mimetic drugs might alleviate the movement disorders in Huntington's chorea. (N Engl J Med 294:1305–1309, 1976) HUNTINGTON'S chorea, like Parkinson's disease, is associated with pathologic changes in the basal ganglions, but is characterized by different motor symptoms.¹ In contrast to the dopamine deficiency in Parkinson's disease, dopamine levels are normal in the corpus striatum of patients with Huntington's chorea, and, in fact, L-dopa exacerbates and dopamine antagonists alleviate the choreic movements.^1,2 Biochemical analysis of samples of corpus striatum obtained post-mortem from a number of choreic patients has shown the following results: an average 85 per cent decline in the activity of glutamic acid decarboxylase,^3,4 the enzyme that synthesizes the inhibitory neurotransmitter, γ-aminobutyric acid (GABA); a pronounced.