SUBSTANCE P-LIKE AND CHOLECYSTOKININ-LIKE IMMUNOREACTIVITY DURING POST-METAMORPHIC DEVELOPMENT OF THE CENTRAL-NERVOUS-SYSTEM IN THE ASCIDIAN CIONA-INTESTINALIS

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 birth-dates 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.