SYNERGISTIC EFFECTS IN THE ALPHA-ADRENERGIC AND BETA-1-ADRENERGIC REGULATIONS OF INTRACELLULAR CALCIUM LEVELS IN STRIATAL ASTROCYTES

1. Using indo-1 as a calcium fluorescent probe, we have observed the following in striatal astrocytes in primary culture. 2. The stimulation of alpha-adrenoceptors induces a rapid rise in cytosolic calcium resulting from an internal calcium mobilization followed by an external calcium influx (4-min duration). 3. The stimulation of beta-1-adrenoceptors evokes only a slight internal calcium mobilization (90-sec duration). 4. The simultaneous stimulation of beta-1- and alpha-adrenoceptors induces a more prolonged calcium influx (10 min). The latter phenomenon could explain the calcium-dependent synergistic effects of alpha-1 and beta stimulation on cAMP production already described in the brain.