Fig. 2. Neurospheres express functional P2 receptors. (A) Neurospheres were loaded with the Ca²⁺ indicator fura-2 AM and stimulated with the P2 receptor agonists ATP, ADP, UTP and UDP (50 µM each). Representative plot of rapid and transient cytosolic Ca²⁺ elevations recorded from a single neurosphere, evoked by successive application (horizontal bars) of nucleotides. (B) Responses to ATP, ADP, UTP and UDP evoked in identical neurospheres, normalized to the ATP response (100%) (mean±s.d., n=14, ^**P<0.01). (C) Dose dependence of the neurosphere response. Ca²⁺ responses to increasing concentrations of either ATP (black), ADP (hatched) or UTP (white) were successively recorded from single neurospheres. The response to 50 µM nucleotide was set to 100% (mean±s.d., n=3-9).