Research Highlight
Astrocytes Change During Postnatal Brain Development
April 2004 — Unique astrocyte territories in the adult brain are likely formed through competition between astrocyte processes, similar to the competitive interactions among neuronal dendritic fields, according to a recently published study by NCMIR researchers Eric A. Bushong, Maryann E. Martone, and Mark Ellisman that examined the fine morphological features of developing astrocytes in the rat brain.
An earlier study by Bushong and his colleagues showed that adjacent astrocytes in the adult brain occupy largely non-overlapping territories. These domains represent a potential level of parcellation of brain microdomains not appreciated from previous studies of the astrocyte.
The present study examined how astrocytes come to occupy these unique domains. The results, published in the April 2004 issue of International Journal of Developmental Neuroscience, showed dramatic changes in astrocytes during the first three postnatal weeks. Protoplasmic astrocytes are heterogeneous in morphology at 1-week postnatum, but a remarkable consistency in morphology develops by 2 weeks of age. During the first two weeks, astrocytes extend stringy, filopodial processes that overlap, and by the third week fine, spongiform leaflet processes appear. The subsequent elaboration of spongiform processes results in the development of boundaries between neighboring astrocyte spaces. Stray processes that encroach on neighboring spaces are eventually pruned by 1 month of age.
Astrocytes have become an important area of study after recent research indicated that they fulfill many roles within the normal brain, such as providing some degree of mechanical integrity to tissue, maintaining the composition of the extracellular milieu, participating in synaptic function and plasticity, providing neurotransmitters and energy substrates to neurons, and regulating blood flow. Accordingly, their elaborate morphology enables protoplasmic astrocytes to maintain a position near neuronal somata and dendrites, synapses, blood vessels, and the margins of the nervous system.
The above image depicts two adjacent astrocytes from the rat brain hippocampus injected with two different color dyes to elucidate their individual morphology and the extent of their interaction. This data set is available for viewing and download from the newly redesigned Cell Centered Database (Record ID: 3wk-both2).
Links to Related NCMIR studies:
Astrocytes Limit CNS Regeneration
Relationship of Astrocytes to Laminar Boundaries in the Adult Brain Examined
