L-Glutamate binding sites of normal and atrophic human cerebellum

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.