Activation of endothelin receptors by sarafotoxin regulates Ca super(2+) homeostasis in cerebellar astrocytes

We carried out experiments designed to investigate the effects of sarafotoxin-6B (SFTx) on (Ca super(2+)) sub(i) in cerebellar astrocytes using the Ca super(2+) indicator fura-2. Both endothelin-1 and sarafotoxin-6B increased (Ca super(2+)) sub(i) in individual cerebellar astrocytes in cell culture. Addition of 50 mM K super(+) produced a small increase in (Ca super(2+)) sub(i) in most cells. This response was blocked by nimodipine. However, nimodipine only slightly blocked the plateau increase in (Ca super(2+)) sub(i) that was formed following activation of endothelin receptors. In conclusion, activation of endothelin receptors by SFTx in cerebellar astrocytes produces both Ca super(2+) mobilization and Ca super(2+) influx. The pathway for Ca super(2+) influx is predominantly a non-voltage-dependent one, although some entry through a dihydropyridine-sensitive pathway also appears to occur.