NEUROHORMONAL CONTROL OF GROWTH AND CARBOHYDRATE-METABOLISM BY THE LIGHT GREEN CELLS IN LYMNAEA-STAGNALIS

The neuroendocrine light green cells (LGCs), 4 clusters of together ∼150 giant neurons in the cerebral ganglia of the freshwater gastropod, Lymnaea stagnalis, have been suggested to be involved in the control of growth. The present study examines in greater detail this role and possible actions on energy metabolism. Growth indices (total body and organ wet and dry weights, as well as protein and DNA contents of the organs) and metabolic indices (tissue lipid, polysaccharide and glucose levels) were compared in LGC extirpated/reimplanted with control groups. LGC extirpation in rapidly growing juvenile snails immediately arrested growth, which was restored by reimplantation of cerebral ganglia with LGCs but not by cerebral ganglia without LGCs, indicating their neuroendocrine control of growth. The LGCs stimulate a pattern of organ growth, which is in proportion to the growth of the whole body except for the shell, which shows a disproportionally faster growth due to calcium deposition over the whole surface. The data on protein and DNA in the organs strongly suggest that the LGCs induce growth by stimulating cell multiplication. The LGCs maintain low tissue glycogen reserves and hemolymph concentrations of both glycogen and glucose. The secretions of these cells stimulate the uptake of glucose by the growing tissues with no apparent effects on lipid metabolism. © 1992.