CYTOLOGICAL APPROACH TO MORPHOGENESIS IN THE PLANARIAN BLASTEMA .2. THE EFFECT OF NEUROPEPTIDES

The regeneration blastema consists of three cell types, undifferentiat ed cells, regenerative cells, and differentiated cells all of which ca n be identified by their ultrastructural characteristics. Quantitative changes in the numbers of these cells within the blastema offer impor tant clues about the detailed process of regeneration. When decapitate d worms were allowed to regenerate in neuropeptide-containing tap wate r, the undifferentiated cells accumulated rapidly and initiated blaste ma formation. These cells were then replaced with regenerative cells, and subsequently with differentiated cells. Ln the non-treated regener ating worms, the proportion of undifferentiated cells was much lower t han in the neuropeptide-treated ones. The results of this study indica te that neuropeptides have a remarkable effect on the early stage of r egeneration in planarians. Immunoelectron microscopy using a gold-conj ugated anti-neuropeptide antiserum revealed the presence of neuropepti des in some kinds of parenchymal cells in the post-blastemal area.