Figure 4. Effects of acetylcholine, epinephrine, and SNI-2011 on NOS activity in isolated parotid acinar cells from young adult or senescent rats. The isolated parotid acinar cells from 10-week-old (Young) or 115-week-old (Old) rats were pre-incubated with DAF-2/DA. Cells suspended with Krebs-Ringer bicarbonate solution were incubated with 1 µM acetylcholine(ACh) (A), 1 µM epinephrine (Epi) (B), and 10 µM SNI-2011 (C). The traces are representative of 3 independent experiments. Acetylcholine, epinephrine, and SNI-2011 were applied as indicated by the arrow. **P < 0.01, ***P < 0.001 vs. the control value.