Phylogenesis of the Bainbridge reflex

Area of Science:

• Cardiovascular Physiology
• Comparative Physiology

Background:

• The Bainbridge reflex describes the increase in heart rate due to venous return.
• Understanding species-specific responses to volume loading is crucial for cardiovascular research.

Purpose of the Study:

• To investigate the effects of acute volume loading on left ventricular (LV) pressure and heart rate.
• To compare these effects across humans, dogs, and baboons to understand the Bainbridge reflex's utilization.

Main Methods:

• Cardiac catheterization was performed in human patients to measure LV pressure and heart rate during volume loading.
• Data were compared with previously collected data from conscious dogs and baboons under similar conditions.

Main Results:

• Volume loading increased LV end-diastolic pressure similarly in humans, dogs, and baboons.
• LV systolic pressure increased in dogs but not significantly in humans or baboons.
• Heart rate increased in humans (+15 bpm), baboons (+37 bpm), and dogs (+88 bpm), with significant differences between species.

Conclusions:

• The Bainbridge reflex is present in primates, including humans.
• The magnitude of the Bainbridge reflex is significantly attenuated in primates compared to nonprimate mammals like dogs.
• Species differences in cardiovascular regulation are evident in response to volume expansion.