[Topographic and chemical study of the GABA synthetizing enzyme in Parkinsonian syndromes].

After a classical neuropathological study assessing the diagnosis, the activity of the GABA synthetizing enzyme, glutamate decarboxylase (GAD), was assayed in 6 brain areas, in 8 cases of Parkinson's disease, 2 cases of idiopathic orthostatic hypotension and 9 control cases carefully matched. The activity of GAD is not impaired, as classically believed, in parkinsonian brains, particularly in substantia nigra and pallidum. This preservation would indicate the absence of lesion of GABAergic neurones in Parkinson's disease. In the cases of other Parkinsonian syndromes, the number of cases studied is too limited to allow any generality; but they are, however reported because of their rarity.