Figure 1.

Calcium oscillation induced by α2AR. (a) Representative images of HeLa cells showing Ca²⁺ response in the continuous presence of norepinephrine (agonist, dose = 100 μM). (b) Representative HeLa cell showing Ca²⁺ response after addition of agonist (norepinephrine, dose = 100 μM) followed by antagonist (yohimbine, dose = 50 μM). Times shown are period elapsed after agonist addition. Antagonist was added at 25 s. Arrows point to cells that show increases in calcium over basal state cells. Cells exposed to antagonist do not show such an increase in any cell over basal state cells. (c) Time course of Ca²⁺ oscillations in the presence of norepinephrine in a single cell. Red arrow indicates addition of norepinephrine. (d) Time course of Ca²⁺ oscillations after addition of norepinephrine (red arrow) followed by yohimbine (black arrow). (e and f) Frequency distribution of the number of Ca²⁺ spikes in cells from (a and b). Number of independent experiments (N_exp) = 5. To see this figure in color, go online.