Genetic background affects cardiovascular responses to obstructive and simulated apnea

Area of Science:

• Cardiovascular Physiology
• Genetics
• Respiratory Physiology

Background:

• Genetic background significantly affects blood pressure and heart rate responses to hypoxia.
• Hypoxia is a known mediator of cardiovascular complications in obstructive sleep apnea (OSA).

Purpose of the Study:

• To investigate if genetic factors influence cardiovascular responses to experimentally induced obstructive apnea (OA) and simulated apnea (SA).

Main Methods:

• Three inbred mouse strains (C57BL/6J, DBA/2J, FVB/J) were used.
• Apnea was induced for 5- and 10-second periods in spontaneously breathing (OA) and mechanically ventilated (SA) animals.
• Autonomic ganglionic blockade was administered using hexamethonium.

Main Results:

• Obstructive apnea (OA) induced a marked hypertensive response in all strains.
• Strain significantly impacted the degree of bradycardia during OA; it was pronounced in C57BL/6J and FVB/J mice, but absent in DBA/2J mice.
• Bradycardia in C57BL/6J mice was abolished during simulated apnea (SA) under mechanical ventilation, while FVB/J mice still exhibited bradycardia, suggesting baroreceptor involvement.

Conclusions:

• Genetic background influences both the pattern and magnitude of cardiovascular responses to apnea.
• DBA/2J mice unexpectedly do not exhibit bradycardia during apnea, unlike their response to hypoxia.
• C57BL/6J mice show apnea-induced bradycardia dependent on thoracic afferent input, while FVB/J mice display baroreceptor-mediated bradycardia.