Figure 4.

Effects of the myosin-Va binding fragment of syntaxin-1A on catecholamine release from chromaffin cells as determined by amperometry. Chromaffin cells were microinjected with syntaxin-1A fragments with potent (syntaxin-1A [191-240]) or lacking potent (syntaxin-1A [191-240 L222E]) myosin-Va-binding activity and then stimulated for 4 s with 60 mM KCl. As controls, cells also were microinjected with distilled water (DW) or not injected (none). (A) Amperometric wave patterns. (B) Number of spikes of catecholamine release. The values represent the means ± SEM, and the numbers of determinations (n) were as follows: None, 15; DW, 11; syntaxin-1A [191-240], 18; and L222E syntaxin-1A, 13. The asterisk (*) represents a significant difference between the results using the two syntaxin-1A fragments (p < 0.05).