The ventilatory (VE) responses to hypercapnia (7% CO2, panel A) and hypoxia (10% O2, panel B) in conscious rats 2 h, and 1, 2, and 5 days after exposure to vehicle (VEH), moderate-, or high-dose of sarin (SM and SH). The reductions of VE, tidal volume (VT) and/or respiratory frequency (fR) responses to hypercapnia or hypoxia immediately (2 h) after SM and SH exposure were recovered 1–2 days after sarin exposure. D1–D5 represents the tests applied 1, 2, and 5 days after exposure. Mean ± SE; n = 12, 8 and 8 for VEH, SM and SH animals, respectively. * P < 0.05, SH or SM vs. VEH group.