CALCIUM-MOBILIZING AND ELECTROPHYSIOLOGICAL EFFECTS OF BRADYKININ ON CORTICAL ASTROCYTE SUBTYPES IN CULTURE

The possible consequences of activating bradykinin (Bk) receptors on i dentified astrocyte subtypes derived from rat cortex have been investi gated in terms of: 1) mobilization of intracellular Ca2+; and 2) elect rophysiological response. Bk induced a rapid, transient rise in intrac ellular Ca2+ in 63% of cortical type-l-like astrocytes and 44% of type -2 astrocytes tested. Experiments involving Ca2+-free conditions sugge sted that the release occurred largely from internal stores in both as trocyte subtypes. Bk receptor activation resulted in an inward current in approximately 10% of each astrocyte subtype tested using the whole -cell patch clamp technique. The use of perforated patch recording con firmed a similar population of cells responsive to Bk. The Bk-induced current was associated with a decrease in membrane conductance. The re versal potential was close to the K+ equilibrium potential, consistent with the closure of K+ channels. The current demonstrated similar EC5 0 values and Hill coefficients and also a marked degree of desensitiza tion for both astrocyte subtypes. Recordings from type-l-like astrocyt es indicated that the receptor mediating the electrophysiological resp onse was of the B2 subtype. The data were consistent with the function al translation of Bk receptor occupation to physiological responses in distinct sub-populations of cortical type-1-like and type-2 astrocyte s. (C) 1993 Wiley-Liss, Inc.