Astrogliosis is a predictable response of astrocytes to various types of injury caused by physical, chemical, and pathological trauma. It is characterized by hyperplasia, hypertrophy, and an increase in immunodetectable glial fibrillary acidic protein (GFAP). As GFAP accumulation is one of the prominent features of astrogliosis, inhibition or delay in GFAP synthesis in damaged and reactive astrocytes might affect astrogliosis and delay scar formation. The aim of this study is to investigate the possibility of utilizing antisense oligonucleotides in controlling the response of astrocytes after mechanically induced injury. We scratched primary astrocyte cultures prepared from newborn rat cerebral cortex with a plastic pipette tip as an injury model and studied the astrogliotic responses in culture. Injured astrocytes became hyperplastic, hypertrophic, and had an increased GFAP content. These observations demonstrate that injured astrocytes in culture are capable of becoming reactive and exhibit gliotic behaviors in culture without neurons. The increase in GFAP content in injured astrocytes could be inhibited by incubating the scratched culture with commercially available liposome complexed with 3' or 5' antisense oligonucleotides (20 nt) in the coding region of mouse GFAP. The scratch model provides a simple system to examine in more detail the mechanisms involved in triggering glial reactivity and many of the cellular dynamics associated with scar formation. Antisense oligonucleotide treatment could inhibit the GFAP synthesis in injured astrocytes, hence it may be applicable in modifying scar formation in CNS injury in vivo.