Figure 5.

Ca²⁺-ATPase inhibitors induce a drastic delay in receptor current recovery. (A) Suction pipette recordings from an isolated ORN, which was stimulated for 1 s with 500 µM IBMX and then allowed to recover either in normal Ringer’s solution, in Ringer’s solution containing 1 mM vanadate, or in a guanidinium-substituted solution with reduced external Na⁺ (5.5 mM) containing 1 mM vanadate. (B) Using the same protocol as in A, a different cell was allowed to recover either in normal Ringer’s solution or in Ringer’s solution containing 90 µM carboxyeosin. Each trace is the average of two to three trials and has been junction corrected for the experiments with vanadate. Gray bars denote the command for the presentation of the IBMX stimulus. Solid bars denote modified solution for response recovery. (C) Mean rate constants for receptor current decay in Ringer’s solution (n = 18), 11 mM Na⁺ (n = 14), 5.5 mM Na⁺ (n = 3), 0 mM Na⁺ (n = 5), nickel (n = 8), 1 mM vanadate (n = 11), vanadate with low Na⁺ (n = 8), and carboxyeosin (n = 46). All rate constants were normalized to the rate constant for current recovery upon return to normal Ringer’s solution in the same cell. Rate constants were obtained as the reciprocal of the time constant of the decaying single-exponential function fitted to each trace using a least-squares algorithm. Error bars represent SEM. Statistical analysis was performed using a one-way ANOVA followed by posthoc analysis using the Bonferroni test with significance set at P < 0.05 (confidence level = 95%) to assess differences between individual groups as specified in the text.