Effect of TTR on calcium. Cultures of DRG neurons were treated with L55P (A) or wild-type (B) TTR and intracellular calcium flux (ΔF/F0) was measured over a 500 sec time course. Addition of L55P elicited greater calcium fluxes than WT. Significantly, calcium entry at growth cones (arrows) occurred earlier than at DRG cell soma. Scale bar is 5 μm.