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SUMMARY Cerebrospinal fluid gamma-aminobutyric acid (CSF-GABA) was analysed by radioreceptor assay in 16 normal controls and 84 patients with various neurological and psychiatric diseases. In patients with spinocerebellar degeneration, neuro-Beh9et's syndrome and Parkinson's disease, CSF-GABA levels were decreased. On the other hand, increased CSF-GABA levels were detected in patients with meningitis. Procedures All individuals were maintained on absolute bed rest and oral intake was avoided for the previous 15 hours. Some of these patients were not medicated. In the others drug therapy was stopped for at least 14 days preceding lumbar puncture with the exception of those with epilepsy. Lumbar puncture were performed at 9 am in the standard fashion with the patients in the lateral decubitus position. Ten ml of CSF was withdrawn and the final 5 ml was immediately frozen in an acetone dry ice tube and kept at -70°C until assay.Assay GABA radioreceptor assay was performed principally by the method of Enna et al.10 For the receptor preparation, crude synaptic membrane was prepared from whole rat brain using a modification of the method of De Robertis et al."1 Briefly, Sprague-Dawley rats (200-250 g) were decapitated and the whole brains were immediately removed. The tissue was homogenised in 10 vol of icecold 0-32 M sucrose by Brinkman Polytron PT-10 homogeniser for 20 s and the homogenate was centrifuged at 900 g for 10 min. The supematant was further centrifuged at 11 500 g for 20 min, and the pellet was resuspended in 10 vol of Tris-HCI buffer (50 mM Tris-HCI buffer, pH 7 6) and kept at -70°C until used. Before analysis, this preparation was thawed and homogenised with a glass-homogeniser in 100 vol of Tris-HCI buffer, then centrifuged at 50000 g for 20 min. The supernatant was discarded and the pellet was resuspended in 100 vol of Tris-HCl buffer containing 0 05% Triton X-100 and incubated in shaking water bath at 37°C for 30 min, then centrifuged at 50 000 g for 20 min, twice. The pellet was resuspended in 20 vol of Tris-HCl buffer to make a tissue concentration of approximately 0-6 mg protein/ml. For the GABA radioreceptor assay, 0 5 ml 257 copyright.

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