L-Glutamate binding sites of normal and atrophic human cerebellum

Abstract

The binding kinetics, pharmacologic properties, ontogeny and localization of L-glutamate binding sites were studied in membrane preparations and sections of normal and olivopontocerebellar atrophy (OPCA) human cerebellum. One binding component was found with a K d value in the order of 150 × 10 −9 M. No significant changes of K d values were observed with age, whereas the highest B max value was observed at the age of 1 year. L-Aspartate, ibotenate, quisqualate and L-homocysteic acid were potent inhibitors of L-[ 3H]glutamate binding. Quantitative densitometric measuremenst indicated the presence of l-glutamate sites in both the molecular and granule cell layer. In OPCA cerebella a very significant decrease of L-[ 3H]glutamate specific binding ( B max was observed, whereas K d values were found unchanged. The pharmacologic properties of L-[ 3H]glutamate binding sites of OPCA cerebellar tissues were similar to those of normal cerebellum. [ 3H]quinuclidinyl benzylate binding, expressed in fmol/mg protein, did not show significant differences between normal and OPCA cerebella.