Figure 5.

Signs of excitability are more evident in MNs derived from GDNF-expressing cells. At 9 days in culture, CTRL-ESC/HB9::GFP (left column) and GDNF-ESC/HB9::GFP (middle column) MNs showed various stages of differentiation. (A–F) show voltage responses to depolarizing and hyperpolarizing current steps (not shown) injected intracellularly. (A,B) Arrowheads denote local responses appearing upon mostly passive electrical properties in both classes of neurons. (C,D) Arrows point towards regenerative responses with mixed sodium and calcium components. (E,F) Repetitive firing of action potentials (APs) in both classes of neurons. GDNF MNs showed larger inward rectification denoted by depolarizing sags upon hyperpolarization and rebound APs (RAPs) upon returning from it. Arrow denotes a putative spontaneous synaptic event (F). (G) The average number of APs, significantly larger in GDNF-expressing cells. (H,I) Neither resting membrane potential (RMP) nor whole neuron input resistance (R_N) were significantly different. (J) Sag inward rectification was significantly larger in GDNF-expressing neurons. (K) RAPs after ending a hyperpolarization step were significantly higher in GDNF expressing neurons. (L) Ca²⁺events was not significantly different between both samples (see C,D). *p < 0.05.