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Distribution pattern of acetylcholinesterase in early embryonic chicken hearts
W H Lamers1, W J Geerts, A F Moorman
1Department of Anatomy and Embryology, University of Amsterdam, The Netherlands.
Insights
Acetylcholinesterase appears in early chicken embryonic hearts, with dynamic changes in expression correlating with cardiac conduction development. This enzyme
Area of Science:
- Developmental Biology
- Cardiovascular Physiology
- Neurobiology
Background:
- Acetylcholinesterase (AChE) plays a crucial role in cholinergic signaling.
- Understanding AChE's role in early heart development is essential for comprehending cardiac conduction.
- Previous studies have not fully elucidated the spatio-temporal expression of AChE during embryonic heart formation.
Purpose of the Study:
- To investigate the developmental appearance and distribution of acetylcholinesterase in early chicken embryonic hearts.
- To correlate AChE expression patterns with the emergence of cardiac conduction pathways.
- To explore the potential role of a cholinergic system in coordinating myocardial contraction before the definitive conductive system forms.
Main Methods:
- Enzyme-histochemical analysis was performed on chicken embryos.
- Embryos were examined across developmental stages from cardiogenic plate to late tubular stages.
- Specific attention was paid to the localization of acetylcholinesterase activity within the developing heart.
Main Results:
- Initially, acetylcholinesterase is present in all myocardial cells.
- AChE selectively disappears from specific ventricular and atrial regions as development progresses.
- High AChE concentrations are observed in the outflow tract, with lower levels in specific atrial and atrioventricular canal regions.
- Re-expression of AChE occurs in the developing ventricular trabeculae and atrioventricular canal.
Conclusions:
- The dynamic expression pattern of acetylcholinesterase in early embryonic chick hearts aligns with regions controlling impulse conduction.
- This suggests a potential cholinergic signal transduction system involved in coordinating myocardial contraction.
- AChE may play a role in establishing coordinated heartbeats prior to the development of the mature cardiac conduction system.
Abstract:
To study the developmental appearance of acetylcholinesterase in early embryonic hearts, an enzyme-histochemical study was carried out in chicken embryos ranging from cardiogenic plate to late tubular stages. Initially acetylcholinesterase is present in all cells of the (future) myocardium. When 13-14 pairs of somites have developed, i.e., shortly before blood propulsion starts, acetylcholinesterase selectively disappears from the ventral and lateral wall of the developing ventricle. Slightly later, when 18-19 pairs of somites have developed, acetylcholinesterase also disappears from the dorsal and anterior wall of the atrium. High concentrations of acetylcholinesterase remain present in the outflow tract and lower concentrations in a continuous tract along the lesser curvature of the heart, the atrial side of the atrioventricular canal, and the left wall of the atrium. In late tubular stages of heart development, acetylcholinesterase is reexpressed in the inner myocardial layer of the ventricle, i.e., in the developing trabeculae and the ventricular side of the atrioventricular canal, where it is continuous with the acetylcholinesterase-expressing cells of the atrial side of the atrioventricular canal. The expression pattern of acetylcholinesterase in early embryonic chick hearts coincides with that of areas that control the conduction of the impulse and may reveal a cholinergic signal transduction system that is responsible for a coordinated contraction pattern of the myocardium prior to the development of the definitive conductive system.