Initial studies in Drosophila advanced the knowledge on CSP-α function ( Zinsmaier et al.,

1994). Later, knock-out mice lacking CSP-α opened new possibilities trans-isomer solubility dmso to study different synapses with high resolution physiological methods ( Fernández-Chacón et al., 2004). We know that 1), CSP-α is not an essential molecular component to execute neurotransmitter release early postnatally in fast synapses like the calyx of Held, but it is required to maintain synaptic function after 3 weeks of age ( Fernández-Chacón et al., 2004); 2), CSP-α cooperates with α-synuclein to maintain the stability of the SNARE-complex that fails to assemble efficiently when CSP-α is absent ( Chandra et al., 2005, Sharma et al., 2011a and Sharma et al., 2011b); and 3), CSP-α is likely most required at the synaptic terminals with high activity ( Fernández-Chacón et al., 2004, García-Junco-Clemente et al., 2010 and Schmitz et al., 2006). Those observations indicate that CSP-α acts as a chaperone to rescue proteins that might become unfolded by the effect of

maintained synaptic activity ( Sharma et al., 2011b). SNAP-25 is the most remarkably reduced synaptic protein in CSP-α knockout mice ( Chandra et al., 2005, Sharma et al., 2011a and Sharma et al., 2011b). Perhaps, other synaptic proteins become functionally altered. A systematic functional study of the complete synaptic vesicle cycle in CSP-α KO mice would be useful to investigate further molecular alterations. Now, using quantal analysis at the neuromuscular MK0683 chemical structure junction (NMJ) we describe a significant decrease in the number of vesicles available for release, likely explained

by a priming defect as a consequence of reduced SNAP-25 levels. In addition, using synaptopHluorin (spH) imaging of the synaptic vesicle cycle at the NMJ, we have found specific alterations in synaptic vesicle recycling that might contribute to nerve terminal progressive degeneration when CSP-α is absent. Specifically, we demonstrate that motorneurons require CSP-α for the maintenance of synaptic release sites and synaptic vesicle recycling. CSP-α KO mice expressing spH developed the strong neurological phenotype that causes mafosfamide early lethality within 1–2 months of age as previously described (Fernández-Chacón et al., 2004). We used the levator auris longus (LAL) nerve–muscle preparation ( Angaut-Petit et al., 1987) to study synaptic transmission with electrophysiology ( Rozas et al., 2011) and with spH imaging ( Tabares et al., 2007). We first studied spontaneous release and detected fibers with “bursts” of miniature end-plate potentials (MEPP), as previously described in CSP-α KO mice ( Ruiz et al., 2008). However, when we excluded those fibers from our analysis, MEPP amplitude was similar in control and mutant synapses (1.03 ± 0.08 mV for wild-type (WT) and 1.