Ontogeny of Vesicular Amine Transporter Expression in the Rat: New Perspectives on Aminergic Neuronal and Neuroendocrine Differentiation

Abstract

Publisher Summary The patterns of expression of vesicular monoamine transporter 1 (VMAT1), VMAT2, and vesicular acetylcholine transporter (VAChT) during ontogenesis of monoaminergic and cholinergic neurons and endocrine cells provide insight into pathways of lineage commitment leading to the final chemical coding of aminergic neurotransmission in the adult rat. Neuroepithelial cells expressing exclusively VMAT2 appear around embryonic day 12 (E12), and are the presumptive neuroblasts giving rise to the monoaminergic cell groups of the central nervous system (CNS). VMAT1 expression at both protein and mRNA levels is absent from CNS neurons at all stages of development examined in this chapter. Monoaminergic neuronal and endocrine cells of the central nervous and gastrointestinopancreatic systems appear to develop via an initial commitment to exclusive expression of one or the other VMAT isoform. In contrast, VMAT1 and VMAT2 are coexpressed during development in adrenomedullary and carotid body neuroendocrine cells and in principal ganglion cells of the sympathetic chain. A subpopulation of postganglionic neurons of the paravertebral sympathetic chain, responsible for innervation of skeletal muscle vasculature and sweat glands, is cholinergic. Cholinergic sympathetic differentiation within the sympathetic chain could conceivably occur at the same time as sympathetic noradrenergic differentiation, as reported in other vertebrate species, although this clearly remains to be determined.