Fig. 2.

Baseline mean arterial blood pressure (MAP, top), heart rate (middle), and frequency of breathing (bottom) values recorded prior to each exposure to hypoxia (H1–H4; 10% O₂, 90% N₂) before and after administration of vehicle (n = 6 rats), N^G-nitro-d-arginine methyl ester (d-NAME; 50 μmol/kg iv, n = 5 rats) or N^G-nitro-l-arginine methyl ester (l-NAME; 50 μmol/kg iv, n = 6 rats). Data are presented as means ± SE of the average of values recorded 5 min prior to exposure to hypoxia. *P < 0.05, significant difference from average of Pre values.