Univ British Columbia, Dept Zool, 4200-6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada;Univ British Columbia, Dept Zool, 4200-6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada;Univ Winnipeg, Dept Biol, 515 Portage Ave, Winnipeg, MB R3B 2E9, Canada;Univ British Columbia, Dept Zool, 4200-6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada;
Sprenger, Ryan J.;Kim, Anne B.;Dzal, Yvonne A.;Milsom, William K.;
Burrowing rodents have a blunted ventilatory response to CO2 in comparison to non-burrowing rodents. Non burrowing rats display a period during development where ventilatory responses to hypercarbia become transiently blunted. This study examined the ventilatory responses to CO2 of rats, hamsters and ground squirrels through neonatal development to determine whether the blunted adult response of burrowing species is a retention of the blunting period seen in rats or present from birth. All three species increased ventilation in response to hypercarbia on the day of birth (70-170% in response to 5% CO2; 100-250% in response to 7% CO2). Rats in our study exhibited the triphasic ventilatory response (when expressed as %Delta) to CO2 previously described. In golden-Syrian hamsters, the ventilatory response slowly and progressively waned to a blunted adult response while in the 13-lined ground squirrels, the early ventilatory response to CO2 decreased within days and remained attenuated through development. Our study shows three distinct developmental patterns in the hypercarbic ventilatory response.