Respiratory phenotype of aged males (18–20 months) at day 3 that underwent MCAO is similar to young males. Respiratory frequency is decreased compared to baseline & sham, p<0.01 (A) resulting in diminished MV under room air conditions compared, p<0.001 (B). These animals also showed a reduced respiratory output over CO2 values ranging from 0–7% CO2 but with no change in slope of the ventilatory response to CO2, p=0.21 (C). Aged stroke animals also exhibited more apneas, p<0.01 (D). In response to hypoxic conditions, there is an effect of stroke on MV (p<0.05) but oxygen sensitivity is not perturbed (slope: p=0.68, E). A-E stroke n=9, sham n= 4.