THE VENTILATORY RESPONSE TO HYPERCAPNIA IN HIBERNATING GOLDEN-MANTLEDGROUND-SQUIRRELS, SPERMOPHILUS-LATERALIS

The hypercapnic ventilatory response of golden-mantled ground squirrel s was characterized an consecutive days throughout single bouts of hib ernation and on the third day of hibernation bouts during the early, m iddle, and late portions of the hibernation season, to determine wheth er ventilatory responses during hibernation are a function of body tem perature or hibernation depth. Our measurements confirm that the hyper capnic ventilatory response of this species during hibernation consist s almost exclusively of increases in respiratory frequency (f(R)); tid al volume (V-T) changed little. No change in f(R) or V-T occurred as i nspired CO2 was increased from 0% to 2%. Between 2% and 8% inspired CO 2, f(R) increased linearly. Respiratory frequency remained constant or decreased slightly as CO2 was elevated beyond 8%. At levels of inspir ed CO2 between 10% and 13%:, animals would initiate arousal from hiber nation and ventilation would increase again through increases in V-T a nd further increases in f(R). No significant interbout or intrabout va riations were observed in any aspect of the hypercapnic ventilatory re sponse. These data indicate that hypercapnic ventilatory sensitivity, if not exclusively a function of body temperature, is consistent betwe en periods of equal body temperature regardless of possible temperatur e-independent changes in hibernation depth.