Long-Term High Salt Intake Involves Reduced SK Currents and Increased Excitability of PVN Neurons with Projections to the Rostral Ventrolateral Medulla in Rats

Figures

• 

  Figure 1. Identification of PVN-RVLM neurons in brain slice for whole-cell patch clamp recording. (a) Red fluorescent tracers were microinjected (100 nL) into the RVLM. (b) Retrograde labeling of the ipsilateral PVN was observed in the dorsal and ventrolateral subnuclei. (c) Image viewed with fluorescence illumination shows a recorded PVN-RVLM neuron containing retrograde tracer. (d) Infrared-DIC image shows the patch electrode positioned on the same PVN-RVLM neuron as (c). 3V: third ventricle.

• 

  Figure 2. HS intake reduces SK currents in PVN-RVLM neurons. (a) The representative voltage-clamp recording traces from NS PVN-RVLM neuron. An outward tail current (black) prior to apamin and the outward tail current (red) after apamin with the total SK current (inset) from the subtraction of the apamin trace (red) from the nonapamin trace (black). (b) The representative voltage-clamp recording traces from HS PVN-RVLM neuron. An outward tail current (blue) prior to apamin and the outward tail current (purple) after apamin with the total SK current (inset) from the subtraction of the apamin trace (purple) from the nonapamin trace (blue). (c) Summary data for apamin-sensitive SK currents between NS controls and the HS group. (d) Summary data for SK current density between NS controls and the HS group showed a significant reduction in SK current density (∗P < 0.05 versus NS controls, unpaired t-test).

• 

  Figure 3. HS intake increases PVN-RVLM neuronal excitability. (a, black) A representative trace of NS control neuronal firing at +200 pA current injection. (a, blue) A representative trace of HS control neuronal firing at +200 pA current injection. (a, red) A representative trace of neuronal firing at +200 pA current injection in NS with apamin. (a, purple) A representative trace of neuronal firing at +200 pA current injection in HS with apamin. (b, left) A current injection stimulus-response curve for NS controls (black) and NS with apamin (red) to graded current injections (∗P < 0.05 versus NS controls without apamin, two-way ANOVA). (b, right) A current injection stimulus-response curve for the HS group (blue) and HS with apamin (purple) to graded current injections (†P < 0.05 versus the HS group without apamin, two-way ANOVA). (c) Summary data for the slope of the linear regression line from the current injection response. The HS group showed a significant increase in the slope compared to NS controls. Treatment with apamin significantly increased the slope in both NS controls and the HS group, but less effect on the slope of the HS group compared to NS controls. (∗P < 0.05 versus NS…

• 

  Figure 4. HS intake decreases interspike interval (ISI) in PVN-RVLM neurons. (a, left) ISI time for NS controls (black) and NS with apamin (red) PVN-RVLM neurons. (a, right) ISI time for the HS group (blue) and HS with apamin (purple) PVN-RVLM neurons. (b) Summary data for the slope of the linear regression line for the ISI in NS controls and NS with apamin, ISI in the HS group and HS with apamin (∗P < 0.05 versus NS; †P < 0.05, versus HS, one-way ANOVA).