Csw loss elevates synapsin and causes stimulation-dependent synapsin loss. A, Representative wandering third instar NMJ synaptic boutons labeled for synapsin (syn, magenta), the vesicular glutamate transporter (vglut, green), and HRP (blue) in w¹¹¹⁸ genetic background control and csw⁵ null mutant. NMJs without stimulation (basal, left) and after acute, 10 min 90 mM [K⁺] depolarizing stimulation (stimulated, right). Scale bar: 2.5 µm. Higher-magnification bouton images are shown below. Scale bar: 1 µm. B, Quantification of synapsin fluorescence intensity in all four conditions (basal and stimulated). Statistical comparisons done using two-way ANOVA, followed by Tukey’s multiple-comparisons test. C, Quantification of synapsin and vglut colocalization in basal (left) and stimulated (right) conditions using PCC analyses. Statistical comparisons done using two-sided t tests. Scatter plots show all the data points with mean ± SEM. Data points: NMJ number. Significance: p < 0.05 (*), p < 0.01 (**), p < 0.0001 (****), and p > 0.05 not significant (n.s.).