Figure 3.
Figure 3. Ca2+-activated K+ channels mediate Idel. (A) Representative whole-cell ATP response profile (10 µM; 5 s; ISI = 180 s) at different Vhold (−80 to 80 mV; 40-mV increment) using Cs+-based pipette solution (S1, S6). Arrows and corresponding open rectangles indicate the periods of Iinst and Idel measurements. (B) Current–voltage relationship of both Iinst (black) and Idel (gray). Individual data points depict mean current densities ± SEM (n = 6). Note that replacing intracellular K+ with Cs+ (inset) has no qualitative effect on Iinst, whereas Idel is essentially abolished. (C) Bar diagram showing the percentage of cells exhibiting Idel in response to ATP (10–100 µM) as a function of the pipette solution’s dominant cation (K+ or Cs+). (D and E) Pharmacological profile of Idel. Representative traces from whole-cell voltage-clamp recordings (D) illustrate ATP-evoked responses (30 µM; ≥1 s) under control conditions (left) and in the presence of TEA (15 mM; Vhold = 10 mV; S4), isomolar Ca2+ (110 nM; Vhold = −40 mV; S3), or iberiotoxin (100 nM; Vhold = −40 mV; S1), respectively (2 min preincubation; right). (E) Bar chart quantifying the effects of pharmacological treatment and reduction of extracellular Ca2+ on both Iinst and Idel (peak responses normalized to control conditions). Data are means ± SEM. Numbers of cells analyzed are indicated above bars. Asterisks (*) denote statistical significance, P < 0.005 (paired t tests comparing peak currents before [control] and during treatment). (F and G) ATP stimulation (100 µM; 3 s) affects spermatogonial Vmem. (F) Representative whole-cell current-clamp recording (S1, S5) illustrating a biphasic change in Vmem. From a resting potential of approximately −40 mV, ATP triggers rapid depolarization toward 0 mV (reversal potential of Iinst; B), which is followed by gradual repolarization and transient hyperpolarization. (G) Quantification of current-clamp recordings. Mean Vmem (±SEM; n = 23) is plotted at rest (without ATP; −39.4 ± 0.4 mV) as well as upon maximum de- and hyperpolarization (−18.1 ± 1.4 mV and −53.1 ± 1.7 mV), respectively. For comparison, resting Vmem was adjusted in a few cells to match −40 mV by small current injections.

Ca2+-activated K+ channels mediate Idel. (A) Representative whole-cell ATP response profile (10 µM; 5 s; ISI = 180 s) at different Vhold (−80 to 80 mV; 40-mV increment) using Cs+-based pipette solution (S1, S6). Arrows and corresponding open rectangles indicate the periods of Iinst and Idel measurements. (B) Current–voltage relationship of both Iinst (black) and Idel (gray). Individual data points depict mean current densities ± SEM (n = 6). Note that replacing intracellular K+ with Cs+ (inset) has no qualitative effect on Iinst, whereas Idel is essentially abolished. (C) Bar diagram showing the percentage of cells exhibiting Idel in response to ATP (10–100 µM) as a function of the pipette solution’s dominant cation (K+ or Cs+). (D and E) Pharmacological profile of Idel. Representative traces from whole-cell voltage-clamp recordings (D) illustrate ATP-evoked responses (30 µM; ≥1 s) under control conditions (left) and in the presence of TEA (15 mM; Vhold = 10 mV; S4), isomolar Ca2+ (110 nM; Vhold = −40 mV; S3), or iberiotoxin (100 nM; Vhold = −40 mV; S1), respectively (2 min preincubation; right). (E) Bar chart quantifying the effects of pharmacological treatment and reduction of extracellular Ca2+ on both Iinst and Idel (peak responses normalized to control conditions). Data are means ± SEM. Numbers of cells analyzed are indicated above bars. Asterisks (*) denote statistical significance, P < 0.005 (paired t tests comparing peak currents before [control] and during treatment). (F and G) ATP stimulation (100 µM; 3 s) affects spermatogonial Vmem. (F) Representative whole-cell current-clamp recording (S1, S5) illustrating a biphasic change in Vmem. From a resting potential of approximately −40 mV, ATP triggers rapid depolarization toward 0 mV (reversal potential of Iinst; B), which is followed by gradual repolarization and transient hyperpolarization. (G) Quantification of current-clamp recordings. Mean Vmem (±SEM; n = 23) is plotted at rest (without ATP; −39.4 ± 0.4 mV) as well as upon maximum de- and hyperpolarization (−18.1 ± 1.4 mV and −53.1 ± 1.7 mV), respectively. For comparison, resting Vmem was adjusted in a few cells to match −40 mV by small current injections.

This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal