Influence of GM1 gangliosides on the growth of cultured rat embryonic serotonergic neurons

GM1 gangliosides were added to the medium of cultured raphe neurons enriched in the serotonergic phenotype in order to study their influence on biochemical and morphological growth parameters of serotonergic neurons. After 2 days of culture in the presence of GM1, specific uptake of serotonin measured by scintillation counting exhibited a moderate but significant increase for a GM1 concentration of 5 X 10(-8) M. Morphological parameters of 5-HT neurons were measured after immunocytochemical staining with specific serotonin antiserum, and digitalization of immunoreactive cells. Eight parameters were studied; for concentrations of 5 X 10(-8) and 10(-7) M of GM1, the absolute neuritic field area and the total length of the segments were significantly increased, whereas the number of neuritic segments, and their mean length were not modified. We conclude that GM1 ganglioside has a significant influence on the growth of serotonergic neurons. Moreover, electron microscopy showed, on treated cultures, a dramatic increase of the number of spicules all along the neuron's process, suggesting that GM1 could act by modifying the attachment of cells to their substrate. The possible molecular mechanisms of the action of GM1 are discussed.