Figure 1.

Coexpression of syntaxin 1A with N-type Ca²⁺ channels in Xenopus oocytes inhibited channel activity. (A) Peak current–voltage relationships of N-type Ca²⁺ channels (α_1Bβ₃α₂) expressed in Xenopus oocytes, in isolation (open circles, n = 4) or with coexpressed syntaxin 1A (filled circles, n = 4). Symbols and error bars display mean ± SEM. (B) N-type Ca²⁺ channel inactivation properties analyzed by use of a “descending staircase” stimulation protocol. Comparison between behavior of channels expressed in isolation (Left) and in the presence of syntaxin 1A (Right). Inward Ba²⁺ currents were evoked by 50-ms depolarizing pulses to 0 mV from a holding potential of −60 mV. After 10 test pulses, holding potential was changed to −80 mV for 10 more test pulses, then further changed to −120 mV for 20 additional test pulses. The interpulse interval (10 seconds) and the test pulse level (0 mV) were kept constant throughout the experiment.