Reorganization of peptidergic systems during brain regeneration in Eiseniafetida (Oligochaeta, Annelida)

After the extirpation of the brain reorganization of the peptidergic (FMRFa mide, neuropeptide Y, proctolin) systems was studied in the newly forming c erebral ganglion of the annelid Eisenia fetida. During regeneration, all im munoreactive fibres appear on the 1st-2nd postoperative day. At the beginni ng of regeneration, immunoreactive neurons and fibres form a mixed structur e in the wound tissue. On the 3rd postoperative day, FMRFamide positive and neuropeptide Y-immunoreactive, while on the 7th postoperative day proctoli n-immunoreactive neurons appear in the loose wound tissue. From the 25th po stoperative day a capsule gradually develops around it. The neurons of the preganglion move to the surface of the newly appearing preganglion. The num ber of these cells gradually increase, and by the 72th-80th postoperative d ays the localization and number of peptide-immunoreactive neurons is simila r to that in the intact one. The neurons of all examined peptidergic systems may originate from the neur oblasts, situated on the inner and outer surface of the intact ganglia (e.g . suboesophageal and ventral cord ganglia). In addition FMRFamide and proct olin immunoreactive neurons may take their derive by mitotic proliferation from the pharyngeal neurons, too.