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Updated: Jun 29, 2026

Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect
Published on: June 14, 2015
Volume loading inhibits baroreflex vagal bradycardia in rats
Shima Morooka1, Naoko Asano, Masayoshi Kobayashi
1Department of Physiology, Mie University School of Medicine, Tsu, Japan.
Abstract:
Volume loading tends to increase blood pressure. Resultant arterial baroreflexes, especially the heart rate component, would counteract renal compensation of volume expansion. In this study, we investigated effect of volume loading on baroreflex vagal bradycardia (BVB) induced by electrical stimulation of the aortic depressor nerves in chloralose/urethane-anesthetized, succinylcholine-immobilized, artificially ventilated rats. As a result, we confirmed that volume loading inhibits BVB. The inhibition was abolished following spinal cord transection at C2. In contrast, volume loading did not affect the bradycardia induced by electrical stimulation of peripheral cut ends of the cervical vagus. These findings suggest that the inhibition of BVB by volume loading is mediated by afferent input which is conveyed in the sympathetic nerves and ascends in the spinal cord, and produced at a central site.
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