Fig. 3

Sphingosine-1-phosphate (S1P) receptor inhibition prevents denervation-induced dendritc remodeling and stabilizes deafferented dendrites. a-d Application of FTY720 (1 μM) into the incubation medium immediately after entorhinal denervation in vitro a, b prevents the protracted reduction in total dendritic length (TDL; n = 9 neurons per group, one cell per culture; Kruskal-Wallis-test followed by Dunn’s post-hoc-test; **, p <0.01; ns, not significant). An initial retraction is observed, which is consistent with the agonist–antagonist properties of FTY720, initially leading to the activation of S1P receptors and their subsequent internalization. c, d FTY720 prevents the denervation-induced destabilization of dendrites (Wilcoxon-Mann–Whitney test with pooled data 0 - 21d; ns, not significant), while having no apparent effect in non-denervated cultures (statistically compared against vehicle-treated cultures, data taken from Fig. 2; Kruskal-Wallis-test followed by Dunn’s post-hoc-test; not significant, not shown). e-h Similar results were obtained in a different set of experiments, in which the S1P-receptor 1 and 3 inhibitor VPC23019 (1 μM) was used e: no change in (F) TDL (n = 7 neurons per group, one cell per culture; Kruskal-Wallis-test followed by Dunn’s post-hoc-test; ns, not significant) and g dendritic elongation and retraction (Wilcoxon-Mann–Whitney test with pooled data 0 - 21d; not significant) following denervation. VPC23019 had no apparent effect on dendrites of granule cells in non-denervated cultures (statistically compared against vehicle-treated cultures, data taken from Fig. 2; Kruskal-Wallis-test followed by Dunn’s post-hoc-test; not significant, not shown) and h clearly prevented the net retraction following entorhinal denervation in vitro. Scale bars in A and E: 50 μm