Figure 5. Concentration-response curves for stimulation of Ca²⁺ release by the α_1A-AR.

Agonist responses represent the difference between basal fluorescence and the peak [Ca²⁺]i (reached within 20 sec of agonist addition), expressed as a percentage of the response to the Ca²⁺ ionophore A23187 (1 µM). Concentration-dependent Ca²⁺ release was stimulated by noradrenaline (panel A), phenylephrine (panel B), A61603 (panel C) or oxymetazoline (panel D). Concentration response curves were performed in the presence or absence of differing concentrations of ρ-Da1a (• control, ▪ 1 nM, ▴ 3 nM, ▾ 10 nM, ♦ 30 nM, ◊ 100 nM, ○ 300 nM). Values are means ± SEM of 3–4 independent experiments.