Pulmonary reflexes and breathing pattern during sleep in the opossum

Area of Science:

• Neuroscience
• Physiology
• Comparative Biology

Background:

• Paradoxical sleep (PS) in mammals, including opossums, is characterized by irregular breathing patterns.
• Slow wave sleep (SWS) typically exhibits regular, even breathing.
• A hypothesis suggested that depressed brainstem reflexes during PS might cause irregular breathing due to reduced pulmonary reflex activity.

Purpose of the Study:

• To investigate the role of pulmonary reflexes in the irregular breathing observed during paradoxical sleep (PS) in opossums.
• To compare the activity of pulmonary reflexes during PS and slow wave sleep (SWS).

Main Methods:

• Pulmonary reflexes were assessed in opossums during both SWS and PS.
• Lung inflation reflexes were tested using airway occlusion at end inspiration and expiration.
• Pulmonary deflation reflexes were evaluated by altering thoracic pressure.

Main Results:

• Pulmonary reflexes activated by lung inflation were present and functional during PS, showing responses comparable to SWS.
• Pulmonary deflation stimulated breathing rate and increased respiratory regularity during PS.
• The findings did not support the hypothesis of maintained depression of pulmonary reflexes during PS.

Conclusions:

• Irregular respiration during paradoxical sleep in opossums is not caused by a depression of pulmonary reflexes.
• Pulmonary reflexes remain active and responsive during PS, similar to their function during SWS.
• The study refutes the link between depressed pulmonary reflexes and irregular breathing in PS.