FIG. 4.

KB-R7943 reversibly blocks the odorant-evoked discharge of lobster ORNs in a dose-dependent manner. A: representative raster displays of action potentials (APs) from a single lobster ORN recorded in the loose-patch configuration in response to increasing odor stimulus intensity (shortest duration at the top of each block) before (top), during (middle), and after (bottom) application of 50 μM of KB-R7943. B: normalized peak AP discharge frequency of the same ORN as in A plotted as a function of odor stimulus duration before, during, and after application of 50 μM of KB-R7943. Data points were fit to a Hill equation. KB-R7943 reversibly blocked the output of the cell. KB-R7943 did not change either spike shape or the spike peak-to-peak amplitude (212.7 pA in control vs. 215.1 pA in presence of 50 μM KB-R7943, insets). C: representative raster displays of APs from a single lobster ORN in response to identical odor stimulus intensity in control condition (top), during applications of increasing concentrations of KB-R7943 (middle), and wash-out (bottom). KB-R7943 reversibly blocked the output of the cell in a dose-dependent manner. D: concentration dependence of KB-R7943 effects on the odorant-evoked ORN discharge. Data points were fit to a Hill equation providing an IC₅₀ of 16.57 μM and a Hill coefficient of 1.74. Data points represent means ± SE of n = 4–8 cells. SN-6, a potent Na⁺/Ca²⁺ exchanger inhibitor, did not block the odorant-evoked AP discharge.