Corticotropin-releasing factor stimulates Ca2+ influx in cultured rat astrocytes

Corticotropin-releasing factor (CRF) increased intracellular Ca2+ concentration in single astrocytes. The effect in increasing intracellular Ca2+ was not observed in Ca2(+)-free solution. Furthermore, CRF at concentrations more than 10 nM stimulated 45Ca2+ uptake in cultured rat astrocytes. The action was blocked by alpha-helical CRF(9-41) in a competitive manner, but not by nifedipine and 3,4-dichlorobenzamil. On the other hand, CRF did not stimulate cAMP formation, cGMP formation and phosphoinositide hydrolysis in astrocytes. These results indicate that CRF increases Ca2+ influx via an activation of CRF receptors in a cAMP-independent mechanism in cultured astrocytes.