Substance P- and cholecytokinin-like immunoreactivity during post-metamorphic development of the central nervous system in the ascidian Ciona intestinalis

Abstract

Following metamorphosis, the neural ganglion of ascidians is thought to be formed via the proliferation of epithelial cells comprising the ciliated duct. In adults, neuronal cell bodies expressing substance P- and gastrin/cholecystokinin-like immunoreactivity exhibit clearly defined patterns of distribution. Previous work shows that these patterns are re-established during regeneration of the adult ganglion. We have used antisera against substance P and cholecystokinin to monitor the formation of these patterns during normal post metamorphic development in Ciona intestinalis. Substance P cells first appear in the ganglion in animals of 1 mm body length. Cholecystokinin antiserum was not used at this stage but revealed a clear adult-like pattern of cells in the anterior region at the 3 to 5-mm stage. Substance P cells do not exhibit an adult pattern until animals have a body length of more than 10 mm. Proliferation in the neural complex was studied using the bromodeoxyuridine/anti-bromodeoxyuridine technique. Results suggest a mechanism whereby cells are born in the ciliated duct and later migrate to the ganglion. Double-labelling experiments indicate that more than 11 days elapse between cell birthdates and the expression of either of the peptides. Data presented suggest that the distributional patterns for these peptides during normal development are similar to those seen during regeneration.