The cessation of breathing in the chicken embryo during cold-hypometabolism

作者：Ide Ryoji; Ide Satoko Tomita; Mortola Jacopo P^*

来源：Respiratory Physiology & Neurobiology, 2017, 242: 19-29.

DOI：10.1016/j.resp.2017.03.004

• Breathing pattern generator
• Breathing frequency
• Control of breathing
• Hypothermia
• Respiratory arrest
• Respiratory rhythm

The avian embryo toward end-incubation combines gas exchange through the chorioallantoic membrane (CAM) and pulmonary ventilation (VE). The main experiments examined breathing activity during coldhypometabolism. Chicken embryos close to hatching were prepared for simultaneous measurements of oxygen consumption ((V) over dot O-2) and carbon dioxide production (V) over dot co(2); open-flow methodology) and breathing frequency (f; barometric technique). As ambient (Ta) and egg temperature (Tegg) dropped, breathing eventually ceased at similar to 18 degrees C, when (V) over dot O-2 and (V) over dot co(2) were 22-28% of the normothermic values. With the eggshell experimentally covered to reduce CAM gas exchange breathing ceased at slightly lower Vol and Vco2 (17-18% of normothermia). Once breathing had stopped, egg exposure to hypoxia (10% or 5% 02) or hypercapnia (3% or 8% CO2) did not resume breathing, which recovered with re-warming. In normothermia, 10% 02 caused hypometabolism and tachypnea; differently, in 5% 02 Vol dropped as much as with hypothermia and breathing stopped, to recover upon return in air. Correlation analysis among Ta, Tegg, (V) over dot O-2 ,(V) over dot co(2) and f during cooling and re-warming indicated thatf followed more closely the changes in Vol and, especially, in (V) over dot co(2) than the changes in Ta or Tegg. Some considerations suggest that in this experimental model the cessation of breathing in hypothermia or severe hypoxia may be due to hypometabolism, while the lack of chemo-responses may have a different mechanistic basis.

• 出版日期2017-8
• 单位McGill