Fig. 6.

Inhibition of PC hydrolysis decreases the ability of ATP to stimulate ERK activity. Primary rat astrocytes were treated without or with the indicated concentrations of D609 for 60 min before addition of ATP (100 μm) for 5 min. In A, phosphorylated ERK1/ERK2 (top panel) and ERK1/ERK2 (bottom panel) were detected by immunoblotting as described in Materials and Methods. InB, ERK activity data (mean ± SEM) were obtained from three independent experiments, each representing different seedings and conducted with duplicate culture plates. “0” indicates cultures treated with ATP only. ERK activity in untreated cultures was 43.3 ± 4.9 pmol phosphate transferred per minute per milligram of protein. **p < 0.001; *p < 0.05 for comparisons of ATP versus D609 + ATP.