Fig. 3. D-Asp release and co-localization within synaptic vesicles.

Extracellular D-Asp concentrations (a) before and (b) after potassium ion stimulation that induced D-Asp release from cerebral ganglia of Aplysia californica. In (a) and (b), the black trace (original) is the electropherogram of the original sample and the red trace (spiked) is the electropherogram of the sample spiked with 1 μM D-Asp, arrows indicate the increase in D-Asp signal due to the addition of 1 μM of standard D-Asp and the change due to potassium ion stimulation (labeled standard and stimulation, respectively). Co-localization of D-Asp and secretory granules in PC12 cells under immunofluorescent microscopic observation of (c) chromogranin A, a marker of secretory granules and (d) D-Asp; (e) merged images of c and d. Scale bar, 10 μm. Higher D-Asp content was observed in synaptic vesicles than in other cell regions in (f) rat Rattus norvegicus and (g) squid Loligo vulgaris. Panels a and b from (Scanlan et al. 2010) are used with permission, c 2010 by John Wiley & Sons, Inc.; panels c–e from (Nakatsuka et al. 2001) are used with permission, © the American Society for Biochemistry and Molecular Biology; and panels f and g are based on the data table in (D’Aniello et al. 2011).