Functional aspects of 5-hydroxytryptamine in early embryogenesis of the sea urchinParacentrotus lividus.

5-Hydroxytryptamine concentrations have been determined in developing sea urchin embryos. Analysis was performed by thin layer chromatography and by fluorimetry. Good correspondence of the results between the two methods was observed. 5-HT was found in the larvae from 33 h of age. The content increased as development proceeded. Treatment of the larvae with iproniazid did not alter the 5-HT content, in contrast to N,N-dimethyltryptamine which caused an increase of the monoamine. The accumulation is thought to depend upon the development of a storage mechanism but the synthesis is considered to start before this storage mechanism is developed. It is suggested that 5-HT is active both at an intracellular and an intercellular level. The intracellular 5-HT acts directly or indirectly on the contractile elements involved in the system responsible for the motility of the cells. In more advanced stages 5-HT acts at an intercellular level as well. In this case it is suggested that the function of 5-HT is analogous to its function in nerve tissue.