NPY-induced VSMC proliferation is mediated by Gi/o proteins. (A) Pertussis toxin (PTX) (100 ng·mL−1, pretreatment for 6 h) blocked the proliferative effect of NPY in rat aortic VSMCs, measured as an increase in [3H]thymidine uptake, at both high- and low-affinity growth peaks. Significant at *, p < 0.05 compared with control using two-way ANOVA followed by Tukey's test. #, p< 0.05 compared with samples treated with NPY only at the same concentration. n = 3 separate experiments. (B) NPY, at all concentrations, inhibited forskolin-stimulated increases in cAMP levels in VSMCs. VSMCs were incubated with IBMX (10−4 mol·L−1) for 5 min, then treated with NPY and forskolin (10−6 mol·L−1) in 0.25% FBS SmBM for 60 min; intracellular cAMP concentrations were measured by ELISA. Significant at *, p < 0.05 compared with forskolin and IBMX alone by one-way RM ANOVA followed by Dunnett's t test. n = 3 separate experiments, 5 wells per experiment.