Membrane currents elicited by angiotensin II in astrocytes from the rat corpus callosum

The corpus callosum (CC) is the main white matter tract in the brain. It consists primarily of axons and glial cells. In the present work, membrane currents generated by angiotensin II (Ang II) in cultured astrocytes from the CC of newborn and 3-week-old rats were studied using the whole-cell voltage-clamp technique. After 4 days of culture, ∼90% of cells were positive to glial fibrillary acidic protein (GFAP), indicating their astrocyte lineage. Ang II elicited inward currents in ∼20% of cells and outward currents in ∼4% of cells from the CC for newborn or 3-week-old rats. The main effect of Ang II on astrocytes from the newborn rat CC was a reduction of membrane conductance, by blocking of delayed rectifier K⁺ currents in 96% of cells. However, no common action of Ang II was observed in cells from 3-week-old rat CC because the responses were quite variable, suggesting the participation of other ion currents. The partial agonist of AT₂ receptors, CGP-42112A, exerted effects on Ang II responses, whereas the AT₁ antagonist ZD7155 did not, suggesting that Ang II responses in CC astrocytes are predominantly mediated by activation of AT₂ receptors. This study is the first to show electrical responses generated by AT₂ receptors in glial cells from the rat central nervous system, and may help gain a better understanding of the functions of Ang II receptors in astrocytes from the rat CC in particular and of glial cells in general.