Prenatal development of cardiovascular regulation in avian species

Abstract

The pulsatile rhythm of the avian embryonic heart is not under autonomic control until late in development, nor are the blood vessels that nourish the different vascular beds of the growing embryo and fetus. Thus, during early development cardiovascular control is mostly dependent on the release of local or systemic vasoactive and cardioactive molecules. It is only in late development that the rapid reflex regulatory mechanisms that characterize adult cardiovascular control start functioning. The current review focuses on how the transition from an aneural cardiovascular system to a neural adult-like system occurs in the chicken fetus, which is the best (and at times the only) known avian species. First, we review the appearance of the different molecular components of a regulatory loop, i.e., nerve fibers, neurotransmitters or receptors. Second, we take a look at the functional integration and maturation of the different afferent and efferent pathways. Third and last, we offer a general overview of humoral and local effectors of cardiovascular control.