Kaohsiung J. Med. Sci. 13: 36-41 (1997)
Origin and morphogenesis of neurons in the frog cardiac ganglion.
R. D. Heathcote
This paper reviews the cellular events underlying the formation of the
cardiac ganglion in the frog. The first neurons become postmitotic at the
end of embryogenesis and begin differentiating in a functioning heart.
Neuronal precursors in the heart continue dividing and differentiating
at least through the beginning of metamorphosis. Since cell death is not
a characteristic of early cardiac ganglion development, proliferation and
differentiation alone regulate the addition of neurons to the heart. As
new neurons are added, their position is unique and reflects their time
of origin. The developmental addition of new neurons to the ganglion is
neither time nor stage dependent, but matches the size of the growing heart,
even into adult life. During this period, the shape and polarity of cardiac
neurons is established through elimination of supernumerary axons that
initially extend throughout the heart. The temporal and spatial accumulation
of cardiac SIF cells occurs in parallel with cardiac neurons and may indicate
a common mechanism underlying the origin of these neural crest derivatives.
These studies contribute to our understanding of the cellular processes
underlying the development of this important autonomic control mechanism
and provide the background for current studies on the regulation of cardiac