Separate factors produced by the CNS of the snail Helisoma stimulate neurite outgrowth and choline metabolism in cultured neurons

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Abstract
Neurons from the snail Helisoma require a brain‐derived factor(s) for neurite outgrowth in both organ and isolated cell culture. This factor is released from the CNS of Helisoma when brains are incubated in defined medium, producing a conditioned medium (CM). In addition to its growth‐promoting activity, CM also enhances total uptake of 3H‐choline and the incorporation of 3H‐choline into specific metabolites: acetylcholine, phosphorycholine and lipid. This choline metabolism‐enhancing factor(s) is distinct and separable from neurite growth‐promoting factor: 1. Over 95% of neurite growth‐promoting activity can be removed from CM by adsorption to a polylysine surface while there is no loss of choline metabolism‐enhancing activity. 2. When central ganglia were treated with anisomycin, a potent inhibitor of molluscan protein synthesis, the choline metabolism‐enhancing activity was completely absent from the resulting CM, while the growth promoting activity was reduced by only 35%. These results suggest that the Helisoma CNS produces a variety of trophic factors that are involved in regulating the interaction between neuronal growth and metabolism.