Autaptic munc18-1 null hippocampal neurons were rescued with a phosphomimetic Munc18-1 mutant, Y473D or wild-type Munc18-1 as control and assessed on morphology and synaptic transmission using whole-cell patch clamp electrophysiology (D) Left: typical responses to hyperosmotic sucrose application (500 mM, 3.5 sec.) used to assess the RRP. Average RRP charge (M18WT: 1.68 ± 0.64 nC, n=13; M18Y473D: 0.08 ± 0.02 nC, n=10, t-test with Welch correction, p = 0.0274). 