Left-hand panels. Total changes in frequency of breathing, Rejection Index (Total Rinx) and Rejection Index/Frequency (Total Rinx/freq) in conscious C57BL6 and Swiss-Webster (Webster) mice recorded during a hypoxic challenge (10% O2, 90% N2) and upon return to room-air (HX – max and RA - max, respectively). Right-hand panels. Total changes in frequency of breathing, Rejection Index (Total Rinx) and Rejection Index/Frequency (Total Rinx/freq) in conscious C57BL6 and B6AF1 mice recorded during a hypoxic challenge (10% O2, 90% N2) and upon return to room-air (HX – max and RA - max, respectively). The data in all panels are presented as mean ± SEM. There were 16 mice in each group. *P < 0.05, significant response. †P < 0.05, Swiss-Webster or