We hypothesized that the ventilatory threshold and sensitivity to
carbon dioxide in the presence of
hypoxia and
hyperoxia during wakefulness would be increased following
testosterone administration in premenopausal women. Additionally, we hypothesized that the sensitivity to
carbon dioxide increases following episodic
hypoxia and that this increase is enhanced after
testosterone administration. Eleven women completed four modified
carbon dioxide rebreathing trials before and after episodic
hypoxia. Two rebreathing trials before and after episodic
hypoxia were completed with
oxygen levels sustained at 150 Torr, the remaining trials were repeated while
oxygen was maintained at 50 Torr. The protocol was completed following 8-10 days of treatment with
testosterone or placebo skin patches. Resting minute ventilation was greater following treatment with
testosterone compared with placebo (
testosterone 11.38 +/- 0.43 vs. placebo 10.07 +/- 0.36 l/min; P < 0.01). This increase was accompanied by an increase in the ventilatory sensitivity to
carbon dioxide in the presence of sustained
hyperoxia (VSco(2)(
hyperoxia)) compared with placebo (3.6 +/- 0.5 vs. 2.9 +/- 0.3; P < 0.03). No change in the ventilatory sensitivity to
carbon dioxide in the presence of sustained
hypoxia (VSco(2
hypoxia)) following treatment with
testosterone was observed. However, the VSco(2
hypoxia) was increased after episodic
hypoxia. This increase was similar following treatment with placebo or
testosterone patches. We conclude that treatment with
testosterone leads to increases in the VSco(2)(
hyperoxia), indicative of increased central chemoreflex responsiveness. We also conclude that exposure to episodic
hypoxia enhances the VSco(2
hypoxia), but that this enhancement is unaffected by treatment with
testosterone.