title: Regulation of breathing and body temperature of a burrowing rodent during hypoxic-hypercapnia.
abstract: Burrowing mammals usually have low respiratory sensitivity to hypoxia and hypercapnia. However, the interaction between ventilation (V), metabolism and body temperature (Tb) during hypoxic-hypercapnia has never been addressed. We tested the hypothesis that Clyomys bishopi, a burrowing rodent of the Brazilian cerrado, shows a small ventilatory response to hypoxic-hypercapnia, accompanied by a marked drop in Tb and metabolism. V, Tb and O(2) consumption (V?O(2)) of C. bishopi were measured during exposure to air, hypoxia (10% and 7% O(2)), hypercapnia (3% and 5% CO(2)) and hypoxic-hypercapnia (10% O(2)+ 3% CO(2)). Hypoxia of 7% but not 10%, caused a significant increase in V, and a significant drop in Tb. Both hypoxic levels decreased V?O(2) and 7% O(2) significantly increased V/V?O(2). Hypercapnia of 5%, but not 3%, elicited a significant increase in V, although no significant change in Tb, V?O(2) or V/V?O(2) was detected. A combination of 10% O(2) and 3% CO(2) had minor effects on V and Tb, while V?O(2) decreased and V/V?O(2) tended to increase. We conclude that C. bishopi has a low sensitivity not only to hypoxia and hypercapnia, but also to hypoxic-hypercapnia, manifested by a biphasic ventilatory response, a drop in metabolism and a tendency to increase V/V?O(2). The effect of hypoxic-hypercapnia was the summation of the hypoxia and hypercapnia effects, with respiratory responses tending to have hypercapnic patterns while metabolic responses, hypoxic patterns.
authors.affiliation: Departamento de Enfermagem Geral e Especializada, Escola de Enfermagem de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, Ribeirão Preto, SP 14040-902, Brazil. habenchu@rfi.fmrp.usp.br
authors.forename: Renata C H
authors.initials: RC
authors.lastname: Barros
authors.forename: Augusto S
authors.initials: AS
authors.lastname: Abe
authors.forename: Evelin C
authors.initials: EC
authors.lastname: Cárnio
authors.forename: Luiz G S
authors.initials: LG
authors.lastname: Branco
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D006935:Hypercapnia / Q000378:metabolism / Q000503:physiopathology*; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption; D012119:Respiration; D012377:Rodentia / Q000502:physiology*