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Hypercapnia attenuates parasympathetic influence on heart rate (1169.10)
Author(s) -
Bloom Jacob,
Ramirez JanMarino,
Garcia Alfredo
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1169.10
Subject(s) - hypercapnia , heart rate , medicine , anesthesia , heart rate variability , respiratory rate , respiratory system , stimulation , cardiology , blood pressure
Hypercapnia is readily recognized as an important stimulus for breathing and is often encountered during cardio‐respiratory conditions such as sleep apnea and SIDS. This on‐going study uses an in vivo approach to examine how hypercapnia influences parasympathetic tone over heart rate and cardiorespiratory coupling. Optogenetic experiments were conducted in mice expressing channelrhodopsin 2 under the regulation of the ChAT promoter. The nucleus ambiguus (NA) was photo‐stimulated (λ=470nm) while breathing 100% O 2 or 95% O 2 /5% CO 2 (hypercapnia). During both 100% O 2 and hypercapnia, the respiratory rhythm was not affected during photo‐stimulation of the NA. However, in 100% O 2 , photo‐stimulation of the NA increased HRV. In contrast, heart rate variability (HRV) was unaffected by photo舉activation of the NA during hypercapnia. Hypercapnia also prevented light‐mediated depression in heart rate. Blockade of β‐receptors, did not affect the ability for hypercapnia to prevent light activated inhibition of heart rate. Thus, hypercapnia appears to attenuate parasympathetic tone over heart rate through a mechanism independent of sympathetic input. These findings have potential implications in understanding the basis of cardio‐respiratory uncoupling found in many conditions such as SIDS and sleep apnea.