NPY potentiates PE-induced MAPK activation through NPY Y5 receptors. Primary cultured cardiomyocytes isolated from mice deficient for either NPY Y1 (Y1 −/−) (A) or Y5 (Y5 −/−) (B) receptor expression were treated with 1 nM NPY and then stimulated by 0.1 nM PE. +/+, Cardiomyocytes from wild-type mice. Activation was measured by detection of phosphorylated p38, ERK, and JNK by using Western blot analysis. Data were quantified by laser-scanning densitometry. Results represent percent increase ± SEM as compared with unstimulated control (n = 3); *, P < 0.05 as compared with the indicate group; NS, not significant; #, P < 0.05 as compared with control.