Voltage-dependent calcium currents are enhanced in nucleus of the solitary tract neurons isolated from renal wrap hypertensive rats

Gleb Tolstykh, Patricia M. De Paula, Steve Mifflin

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Abstract

The nucleus of the solitary tract (NTS) is the central site of termination of baroreceptor afferents. We hypothesize that changes occur in voltage-gated calcium channels (VGCCs) within NTS neurons as a consequence of hypertension. Whole-cell patch-clamp recordings were obtained from adult normotensive (109±2 mm Hg; n=6 from 6 sham-operated and 31 nonsurgically treated) and hypertensive (158±6 mm Hg; n=24) rats. In some experiments, 4-(4-[dihexadecylamino]styryl)-N-methylpyridinium iodide was applied to the aortic nerve to visualize NTS neurons receiving baroreceptor synaptic contacts. Ba currents (500 ms; -80 mV prepotential; 500 ms voltage steps in 5-mV increments to +15mV) peaked between -20 and -10 mV and were blocked by 100 μm of Cd. Peak VGCCs were not different comparing non-4-(4-[dihexadecylamino] styryl)-N-methylpyridinium iodide-labeled and 4-(4- [dihexadecylamino]styryl)-N- methylpyridinium iodide-labeled NTS neurons in hypertensive and normotensive rats. The peak VGCC was significantly greater in cells from hypertensive compared with normotensive rats for both non-DiA-labeled (P=0.02) and DiA-labeled (P=0.04) neurons. To separate high-voltage activated (HVA) and low-voltage activated (LVA) components of VGCCs, voltage ramps (-110 mV to +30 mV over 50 ms) were applied from a holding potential of -60 mV (LVA channels inactivated) and a holding potential of -100 mV (both LVA and HVA currents activated). HVA currents were subtracted from HVA+LVA currents to yield the LVA current. Peak LVA currents were not different between hypertensive (8.9±0.8 pA/pF) and normotensive (7.8±0.6 pA/pF) groups of NTS neurons (P=0.27). These results demonstrate that 4 weeks of renal wrap hypertension induce an increase in Ca influx through HVA VGCCs in NTS neurons receiving arterial baroreceptor inputs.

Original languageEnglish
Pages (from-to)1163-1169
Number of pages7
JournalHypertension
Volume49
Issue number5
DOIs
Publication statusPublished - 1 May 2007

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Keywords

  • Arterial hypertension
  • Baroreflex
  • Calcium channels
  • Central nervous system
  • Ion channels
  • Nucleus of the solitary tract

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