CEREBELLAR EXCITATORY AND INHIBITORY AMINO-ACID RECEPTORS IN MULTIPLESYSTEM ATROPHY

We studied excitatory and inhibitory amino acid binding sites autoradi ographically in control and multiple system atrophy (MSA) cerebella. W ithin the dentate nucleus (DN) of MSA specimens, we found a significan t increase in the level of GABA(A), benzodiazepine, and metabotropic b inding sites compared with controls. In the granule cell layer, kainat e, N-methyl-D-aspartate, and GABA(A) binding sites were all decreased significantly in MSA specimens compared with controls. In the molecula r layer of MSA cerebellum, pha-amino-3-hydroxy-5-methylisoxazole-4-pro pionate binding sites were decreased significantly compared with contr ols. Cerebellar cortical binding site decreases are likely due to Purk inje and granule cell loss. The increase of binding site levels in DN of MSA specimens may represent receptor up-regulation reflecting loss of descending inhibitory Purkinje cell and ascending excitatory affere nts to the DN.