Effect of probenecid on resting Ca2+and resting membrane conductance. (A) Resting rhod-2 fluorescence level (normalized to the initial value; initialF0) along the course of experiments designed to test the effect of acute application of probenecid. As the exact timing of pulses delivery and of probenecid (or control solution) application and wash-out were not identical for all experiments, data points from each and every fiber tested are shown, with each symbol type corresponding to a distinct fiber. Red symbols are from fibers challenged with probenecid. Black symbols are from fibers challenged with the control protocol. Open symbols correspond to data collected before application and after wash-out of the test solution (probenecid or control), whereas corresponding filled symbols show data collected in the presence of the test solution. The inset shows the raw data while the main panel shows the same data after normalization by a linear function fitted to the data points before the application of probenecid (see the text describing Fig. 6 for details). In one control fiber (squares), depolarizing pulses in the presence of the test-control (DMSO containing) solution were applied much later than in all other fibers and wash-out was not implemented. The bar graphs at the bottom show the mean (±SD) values for F0/initialF0 calculated from the above datasets, during probenecid (or DMSO for the control experiments) application and after wash. For this, for each fiber, all F0/initialF0 values obtained (1) during the test period and (2) after wash were averaged. Data are from six fibers from three mice (control) and nine fibers from four mice (probenecid). (B) Resting membrane conductance along the course of the same experiments as in A, assessed from the change in membrane current elicited by a 20-mV hyperpolarization from the holding voltage. The inset shows the raw values while the main graph shows the values normalized to the initial conductance level. The bar graphs at the bottom show the mean (±SD) values for normalized conductance calculated from the above datasets during probenecid (or DMSO) application and after wash.
Figure 6.

Effect of probenecid on resting Ca 2+ and resting membrane conductance. (A) Resting rhod-2 fluorescence level (normalized to the initial value; initialF0) along the course of experiments designed to test the effect of acute application of probenecid. As the exact timing of pulses delivery and of probenecid (or control solution) application and wash-out were not identical for all experiments, data points from each and every fiber tested are shown, with each symbol type corresponding to a distinct fiber. Red symbols are from fibers challenged with probenecid. Black symbols are from fibers challenged with the control protocol. Open symbols correspond to data collected before application and after wash-out of the test solution (probenecid or control), whereas corresponding filled symbols show data collected in the presence of the test solution. The inset shows the raw data while the main panel shows the same data after normalization by a linear function fitted to the data points before the application of probenecid (see the text describing Fig. 6 for details). In one control fiber (squares), depolarizing pulses in the presence of the test-control (DMSO containing) solution were applied much later than in all other fibers and wash-out was not implemented. The bar graphs at the bottom show the mean (±SD) values for F0/initialF0 calculated from the above datasets, during probenecid (or DMSO for the control experiments) application and after wash. For this, for each fiber, all F0/initialF0 values obtained (1) during the test period and (2) after wash were averaged. Data are from six fibers from three mice (control) and nine fibers from four mice (probenecid). (B) Resting membrane conductance along the course of the same experiments as in A, assessed from the change in membrane current elicited by a 20-mV hyperpolarization from the holding voltage. The inset shows the raw values while the main graph shows the values normalized to the initial conductance level. The bar graphs at the bottom show the mean (±SD) values for normalized conductance calculated from the above datasets during probenecid (or DMSO) application and after wash.

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