Fig. 3.

Progressive changes in breath holding duration (expiratory time) in SWR/J and C57/BLJ mice with repeated hypoxic exposures. Since the C57/BLJ mice underwent an increased number of trials, their overall exposure to hypoxia was increased compared with that of SWR/J mice. Data for the initial 4 trials, the middle AR trial, and the terminal 4 trials are shown. Note the increased duration of gasp-associated breath holding in C57/BLJ mice as opposed to SWR/J mice. Also note the increasing duration of breath holds with the increasing number of trials.