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. 2013 Aug 15;305(7):R780–R792. doi: 10.1152/ajpregu.00029.2013

Fig. 7.

Fig. 7.

The effects of 15% CO2 on the transient A current with either pHo or pHi held constant. A and B: representative family of transient A currents in control (5% CO2) (A) and isohydric hypercapnia (IH) (15% CO2) (B) aCSF. IH solution decreased the transient A current. Arrows show times at which the current amplitudes were determined. C: paired plot of A current amplitude in control (5% CO2) and in IH (15% CO2) solutions for six LC neurons. Note that 15% CO2 IH solutions significantly inhibited Imax of the transient A current (*P < 0.05) despite the fact that pHo did not change. D: trace of the effect of HA (15% CO2) on the pHi of an LC neuron. pHi was measured by fluorescence imaging microscopy of the pH-sensitive dye pyranine, injected into the neuron from the patch pipette. Note the reversible hypercapnia-induced acidification of the neuron when pHi was not clamped. The color images show a pyranine-loaded LC neuron soma. A shift from green to blue fluorescence indicates acidification. Bottom: associated transient A current traces in control (5% CO2; left traces) and in 15% CO2 (right traces). Note that when hypercapnia was allowed to acidify the neuron, the transient A current was decreased. E: trace of the effect of HA (15% CO2) on the pHi of an LC neuron when pHi was clamped. Note the lack of an effect of hypercapnia on pHi. The color images show a pyranine-loaded LC neuron soma whose pHi was clamped during hypercapnic exposure. Bottom: associated transient A current traces in control (5% CO2; left traces) and in 15% CO2 (right traces). Note that when the LC neuron was exposed to hypercapnia while its pHi was maintained constant (i.e., clamped), the transient A current was still decreased by hypercapnia. F: inhibition of the maximum transient A current upon exposure to hypercapnic aCSF (15% CO2) with pHi clamped (gray bar) or not clamped (black bar). The bars represent the mean % inhibition of the maximum transient A current ± SE; n = 3. Note that hypercapnia inhibited the maximum transient A current to the same extent regardless of whether pHi was allowed to acidify or not.