BRAIN GRAFTS OF CEREBRAL GANGLIA HAVE EFFECTIVENESS IN GROWTH RESTORATION OF DAMAGED HELIX-ASPERSA MESOCEREBRUM

The microsurgical extirpation of the mesocerebrum from the brain of fa st-growing juvenile snails (Helix aspersa aspersa: H.a.a) stops their growth. This suggests that neurosecretory cells of the mesocerebrum se crete a growth hormone. Neural grafting has been used as a tool to res tore the impaired growth function after mesocerebrum removal in juveni le H.a.a snails. The transplantation of desheathed cerebral ganglia (C G) (i.e. CG with their glioconjunctive outer covering removed), into t he place where the mesocerebrum had been re-established growth which d epended on the age of the donors. For the grafts of H.a.a CG into H.a. a, it was CG from the youngest donors that restored growth best. Howev er, the CG of adult snails still conserved a slight growth-stimulating activity. Transplantation of the CG from the large, fast-growing sub- species H. aspersa maxima (H.a.m), into the brain of H.a.a with mesoce rebrum removed induced faster growth than the H.a.a CG probably becaus e of a more abundant secretion of growth hormone. Our results show tha t intracerebral CG grafts are well tolerated in snails and that labeli ng of the neurones of the transplanted CG with a vital fluorescent sta in (Fast blue), allowed the observation, over several months, of their integration into the lesion zone of the host brain.