POSTNATAL-DEVELOPMENT OF INTERLAMINAR ASTROGLIAL PROCESSES IN THE CEREBRAL-CORTEX OF PRIMATES

Long astroglial processes traversing several cortical laminae appear t o be characteristic of primate brains. Whether interlaminar processes develop as a modification of radial glia or are truly postnatal elemen ts stemming from stellate astroglia, could be assessed by analyzing th eir early developmental stages. A survey of glial fibrillar acidic pro tein immunoreactive (GFAP-IR) astroglial interlaminar processes in the cerebral cortex of Ceboidea monkeys at various postnatal developmenta l ages, and in human cortical samples of a ten day and a seven year ol d child disclosed that such processes develop postnatally. At one mont h of age GFAP-IR interlaminar processes in monkeys were scarce and sho rt in most frontal, parietal or occipital (striate) cortical areas, ex cept for sulcai (principal and orbital suici) and temporal cortical ar eas. Some processes were weakly positive for vimentin, and these were most abundant in ventral temporal cortical areas. At two months of age processes were present in all these areas, albeit in restricted patch es and significantly shorter than in adults. The expression of this pa ttern was increased at seven months of age. At three years of age almo st every area showed abundant processes and with lengths comparable to the adult Ceboidea individuals. In humans, at 10 days of age long int erlaminar processes were readily apparent in a frontal cortex sample, becoming most apparent at the age of seven years although not reaching yet the adult characteristics as described previously. Conclusions: ( 1) GFAP-IR interlaminar processes develop postnatally, thus typifying a subtype of the classical stellate forms; (2) they bear no obvious di rect;relationship with radial glia; (3) their development is not conte mporary among the various cortical regions. These long cellular proces ses represent an addition to those already described for other astrogl ial cell types in the adult mammalian brain (Golgi-Bergmann glia, tani cytes, Muller cells). (C) 1997 ISDN. Published by Elsevier Science Ltd .