The extracellular matrix in the mature brain: its reactions to endo-alpha-N-acetylgalactosaminidase and collagenase

The hippocampal subiculum in the adult rat brain contains many neurons with nerve cell surface glycoproteins which are linked by collagenous ligands t o perineuronal proteoglycans, The nerve cell surface glycoproteins or their terminal N-acetylgalactosamines are digested by endo-alpha-N-acetylgalacto saminidase. The terminal N-acetylgalactosamines linked by the collagenous l igands are not digested by endo-alpha-N-acetylgalactosasminidase. The colla genous ligands associated with the terminal N-acetylgalactosamines were dig ested by collagenase. The newly exposed terminal N-acetylgalactosamines by this collagenase incubation were digested by endo-alpha-N-acetylgalactosami nidase. These findings on the rat agree with those obtained in our previous studies of the adult mouse brain samples. Furthermore they emphasize our h ypothetical model that the perineuronal proteoglycans are related - via col lagen ligands - with the nerve cell surface glycoproteins.