Fig. 4.

Summary of mean volume changes in PC12 dense core vesicles treated with l-DOPA and/or reserpine. Although vesicle volumes were determined for a total of five separate groups of cells (i.e., two control groups; see Materials and Methods), measurements from the separate control groups have been combined and labeled Pooled Controls in this figure so that the changes in vesicle volume can be compared directly with the amperometry results shown in Figure 2. Error bars represent mean ± SEM of mean volume values from all control cells (n = 23), cells exposed to l-DOPA (n = 10) or reserpine (n = 9), or both simultaneously (n = 9). An average of 42 ± 3 vesicles was measured per cell. Values marked with *** are statistically different with p < 0.001; *indicates a significant difference with p < 0.05 versus pooled controls (Student's t test). Those values marked with δδ and δ are significantly different from separate controls, withp < 0.01 and p < 0.05, respectively. Although mean values are shown in this figure, the same statistical trends were observed when the data were pooled from each group and compared statistically.