FIG. 8.

Simple paired-pulse depression of bipolar neurons stimulated to physiological membrane potentials. A, left: raw capacitance of bipolar neuron terminal voltage clamped at −60 mV, loaded with 0.5 mM EGTA and stimulated with two 250-ms depolarizations to −30 mV with a 50-ms interval between depolarizations. A, middle: different bipolar terminal stimulated the same as at left, only to a membrane potential of −28 mV. A, right: different bipolar terminal stimulated the same as at left, only to a membrane potential of −25 mV. B, left: raw capacitance of bipolar neuron terminal voltage clamped at −60 mV, loaded with 10 mM EGTA, and stimulated with two 250-ms depolarizations to −30 mV with a 50-ms interval between depolarizations. B, middle: different bipolar terminal stimulated the same as at left, only to a membrane potential of −28 mV. B, right: different bipolar terminal stimulated the same as at left, only to a membrane potential of −25 mV. C, left: composite capacitance jump data for all terminals loaded with 0.5 mM EGTA. The black bar (leftmost within depolarization protocol) is the capacitance jump from the 1st 250-ms depolarization, whereas the white bar (rightmost within protocol) represents the capacitance jump from the 2nd 250-ms depolarization started 50 ms after the cessation of the 1st stimulation. The 1st and 2nd depolarizations were not significantly different (P < 0.05) for any protocols. C, right: composite capacitance jump data for all terminals loaded with 10 mM EGTA. The black bar (leftmost within depolarization protocol) is the capacitance jump from the 1st 250-ms depolarization, whereas the white bar (rightmost within protocol) represents the capacitance jump from the 2nd 250-ms depolarization started 50 ms after the cessation of the 1st stimulation. The 1st and 2nd depolarizations were not significantly different (P < 0.05) for any protocols.