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Development of heart rate irregularities in chick embryos
J Höchel1, R Akiyama, T Masuko
1Humboldt-Universität zu Berlin, Institut für Biologie, AG Perinatale Anpassung, 10115 Berlin, Germany.
Insights
Heart rate irregularities in chick embryos increase significantly during development. Rapid heart rate decelerations are linked to the parasympathetic nervous system, while accelerations have less clear autonomic control.
Area of Science:
- Embryology
- Cardiovascular Physiology
- Developmental Biology
Background:
- Heart rate (HR) irregularities, defined as significant fluctuations (>10 beats/min), are crucial indicators of embryonic development.
- Understanding the autonomic nervous system's role in regulating fetal heart rate is vital for assessing developmental health.
Purpose of the Study:
- To characterize the development of heart rate irregularities in chick embryos from day 11 to day 19 of incubation.
- To investigate the autonomic nervous system's involvement in specific heart rate patterns observed during embryonic development.
Main Methods:
- Instantaneous heart rate (IHR) was continuously monitored via arterial blood pressure in chick embryos.
- Gas exchange was maintained through the eggshell and chorioallantoic membrane.
- Autonomic drugs were administered intravenously to assess their effects on HR patterns.
Main Results:
- Baseline HR remained stable until days 12-13, after which transient decelerations (V pattern) emerged and increased in frequency and magnitude.
- Acceleration patterns (lambda, avian omega, periodic) appeared later, with IHR becoming increasingly irregular towards hatching.
- Parasympathetic nervous function mediated rapid HR decelerations, but sympathetic agents showed inconsistent effects on acceleration patterns.
Conclusions:
- Chick embryo heart rate exhibits distinct patterns of irregularity that evolve throughout late incubation.
- Parasympathetic activity is a primary driver of HR deceleration, while sympathetic system involvement in acceleration is less defined.
- These findings provide insights into the maturation of cardiovascular autonomic control during embryonic development.
Abstract:
Heart rate (HR) irregularities in chick embryos were defined as large fluctuations (>10 beats/min) comprising irregular, brief deceleration and/or acceleration of instantaneous HR (IHR). IHR was determined directly from the arterial blood pressure while adequate gas exchange was maintained through an eggshell and chorioallantoic membrane. Five embryos were examined on each day from day 11 to day 19 of incubation. Baseline HR was stable until day 12-13, and on around day 13-14 transient, rapid deceleration of HR (termed V pattern) began to appear, with a subsequent increase in its frequency and magnitude. The acceleration patterns (lambda, avian omega, and periodic patterns) appeared later, and the IHR became increasingly irregular, with additional, spontaneous deceleration and acceleration patterns toward hatching. Additional experiments with intravenous administration of autonomic drugs clearly showed that rapid deceleration of HR was mediated by parasympathetic nervous function but did not always show clear relations of sympathomimetic and sympathetic blocking agents to the acceleration patterns.