Article Figures & Data
Figures
- Figure 1.
TASK-3 is expressed in CA1 SO interneurons. A, Low-power (10×) image of a coronal section of adult mouse hippocampus immunolabeled with TASK-3 antibody (green). TASK-3 immunoreactivity is seen throughout the hippocampus. B, High-power (40×) image of CA1 SO. C, High-power (40×) image of a TASK-3-positive interneuron from a juvenile (P16) mouse. D, TASK-3 immunoreactivity (red) colocalizes with GAD67 immunoreactivity (green), a marker for GABAergic interneurons. E, TASK-3 (green) is found in parvalbumin (PARV) (red) -positive interneurons. F, In mice expressing EGFP in a subset of GAD67-positive interneurons, TASK-3 immunoreactivity (red) is present in some neurons expressing EGFP (green). G, Summary of the fraction of TASK-3-positive cells in CA1 SO that also expressed GAD67, parvalbumin, or EGFP under the GAD67 promoter (GAD67-EGFP). H, Summary of the fraction of cells expressing each marker that also express TASK-3. This fraction was calculated by dividing the number of colocalized cells by the total number that express each marker. For GAD67-EGFP, n = 13 sections, four animals; PARV and GAD67, n = 6 sections, three animals. Error bars equal SEM. Scale bars, 50 μm.
- Figure 2.
A pH-sensitive potassium current is present in some CA1 SO interneurons. A, Whole-cell voltage-clamp recording of a pH-sensitive interneuron. Ai, The holding current became slightly more negative after bath acidification and more positive after alkalization. The input resistance decreased after alkalization, indicating that a pH-sensitive conductance was increased. Aii, Current–voltage relationship in response to voltage steps from −125 to −65 mV at each pH. The pH-sensitive current was obtained by subtracting the control current from current obtained in high or low pH. The GHK fit for each curve is represented by the dotted (pH 6.4) and solid (pH 8.4) lines. Aiii, Representative example neurolucida drawing of a pH-sensitive neuron. Scale bar, 100 μm. B, Whole-cell voltage-clamp recording of a pH-sensitive interneuron that responded to acidification. Bi, The holding current became more negative after bath acidification and more positive after alkalization (top). The input resistance increased with acidification and decreased with alkalization (bottom). Bii, Current–voltage relationship of the pH-sensitive current. Biii, Neurolucida drawing of this pH-sensitive neuron. s.o., Stratum oriens; s.p., stratum pyramidale. Scale bar, 100 μm. C, Summary of the effect of pH on holding current in all pH-sensitive cells. C, D, E, H, Open gray circles and dotted lines represent individual cells, and filled black circles and solid lines represent the mean data. D, Summary of the effect of pH on input resistance. E, Comparison of the magnitude of the current activated in acidic and basic solutions, measured at a holding potential of −115 mV. F, Summary of the current–voltage relationship of interneurons in 3.5 mm extracellular K+ (black circles) and 8.5 mm extracellular K+ (gray squares). The GHK fit (dotted lines) has been shifted by 9 mV to account for the difference between calculated and observed reversal potentials. Only cells that exhibited a pH-sensitive current that reversed within the range tested and that had a decrease in input resistance during bath alkalization were included in this and subsequent analyses (n = 9). G, Example of a whole-cell current-clamp recording of a neuron that hyperpolarized in base. H, Summary of the change in resting potential during alkalization. Error bars equal SEM.
- Figure 3.
A subset of CA1 SO interneurons contain a pH and bupivacaine-sensitive current. A, Whole-cell voltage-clamp recording of a pH- and bupivacaine-sensitive neuron. The holding current became more positive after the pH was increased and returned to control levels after bupivacaine (20 μm) application (top). The input resistance decreased in pH 8.4, which was reversed after application of bupivacaine (bottom). B, Current–voltage relationship of the base (black) and bupivacaine (gray)-sensitive current. C, Example neurolucida drawing of a pH- and bupivacaine-sensitive cell. s.o., Stratum oriens; s.p., stratum pyramidale. D, Summary of the current–voltage relationship for the base-sensitive current. The GHK fit (dotted lines) has been shifted by 9 mV to account for the difference in reversal potentials. E, Summary of the effect of base and base plus bupivacaine (8.4+Bup) on holding current. E, F, Open gray circles and dotted lines represent individual cells, and filled black circles and solid lines represent the mean. F, Summary of the effect of pH on input resistance. Error bars equal SEM.
- Figure 4.
Many interneurons did not exhibit TASK-like currents. A, Whole-cell voltage-clamp recording of a pH- and bupivacaine-insensitive neuron. Neither the holding current (top) nor input resistance (bottom) changed in high pH or high pH and 20 μm bupivacaine. B, Subtracted current–voltage relationship for the same cell as in A. Bup, Bupivacaine. C, Neurolucida drawing of the pH and bupivacaine-insensitive cell in A. s.o., Stratum oriens; s.p., stratum pyramidale. D, Whole-cell voltage-clamp recording of an anomalous pH-sensitive neuron. Both the holding current (top) and input resistance (bottom) changed in both low and high pH. E, Subtracted I–V plot for the same cell as in D. The current–voltage relationship deviated from the expected GHK relationship and showed a large degree of rectification. F, Example neurolucida drawing of a pH-sensitive cell with an ambiguous I–V.
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