Astrocytes constitute the most abundant cell type in the nervous system. Under physiological conditions, they respond to the stimuli to which neurons are also responsive. The use of astrocytoma cell lines with well-defined morphological and functional markers has been helpful for addressing the mechanisms of signal transduction that operate in the nervous system. On the basis of the effects produced by agonists of different types of receptor (muscarinic ACh receptors, thrombin receptors, phospholipases A2 receptors and tumor necrosis factor alpha receptors), several different transcriptional programs that involve the MAP kinase-cytosolic phospholipase A2 system and the transcription factor NF-kappaB have been described.