A-type K+ channels contribute to the prorenin increase of firing activity in hypothalamic vasopressin neurosecretory neurons

Soledad Pitra, Javier Eduardo Stern

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Recent studies have supported an important contribution of prorenin (PR) and its receptor (PRR) to the regulation of hypothalamic, sympathetic, and neurosecretory outflows to the cardiovascular system, including systemic release of vasopressin (VP), both under physiological and cardiovascular disease conditions. Still, the identification of precise cellular mechanisms and neuronal/molecular targets remain unknown. We have recently shown that PRR is expressed in VP neurons and that their activation increases neuronal activity. However, the underlying ionic channel mechanisms are undefined. Here, we performed patch-clamp electrophysiology from identified VP neurons in acute hypothalamic slices obtained from enhanced green fluorescent protein-VP transgenic rats. Voltage-clamp recordings showed that PR inhibited the magnitude of A-type K+ current (IA; ~50% at -25 mV), a subthreshold voltage-dependent current that restrains VP firing activity. PR also increased the inactivation rate of IAand shifted the steady-state voltage-dependent inactivation function toward more hyperpolarized membrane potential (~7 mV shift), thus resulting in less channel availability to be activated at any given membrane potential. PR also inhibited a sustained component of IA(“window” current). PR-mediated changes in action potential waveform and increased firing activity were occluded when IA was blocked by 4-aminopyridine. Finally, PR failed to increase superoxide production within the supraoptic nucleus/paraventricular nucleus, and PR excitatory effects persisted in slices treated with the SOD mimetic tempol. Taken together, these experiments indicated that PR excitatory effects on vasopressin neurons involve inhibition of IA, due, in part, to increases in its voltage-dependent inactivation properties. Moreover, our results indicate that PR effects did not involve an increase in oxidative stress. NEW and NOTEWORTHY Here, we demonstrate that prorenin/the prorenin receptor is an important signaling unit for the regulation of vasopressin firing activity and, thus, systemic hormonal release. We identified A-type K+ channels as key molecular targets mediating prorenin stimulation of vasopressin neuronal activity, thus standing as a potential therapeutic target for neurohumoral activation in cardiovascular disease.

Original languageEnglish (US)
Pages (from-to)H548-H557
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume313
Issue number3
DOIs
StatePublished - Jan 1 2017

Fingerprint

Vasopressins
Renin
Neurons
Membrane Potentials
Cardiovascular Diseases
Transgenic Rats
Supraoptic Nucleus
4-Aminopyridine
Paraventricular Hypothalamic Nucleus
Electrophysiology
Cardiovascular System
Ion Channels
Superoxides
Action Potentials
Oxidative Stress

Keywords

  • Cardiovascular
  • Kcurrent
  • Prorenin receptor
  • Superoxide
  • Supraoptic nucleus

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Cite this

A-type K+ channels contribute to the prorenin increase of firing activity in hypothalamic vasopressin neurosecretory neurons. / Pitra, Soledad; Stern, Javier Eduardo.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 313, No. 3, 01.01.2017, p. H548-H557.

Research output: Contribution to journalArticle

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abstract = "Recent studies have supported an important contribution of prorenin (PR) and its receptor (PRR) to the regulation of hypothalamic, sympathetic, and neurosecretory outflows to the cardiovascular system, including systemic release of vasopressin (VP), both under physiological and cardiovascular disease conditions. Still, the identification of precise cellular mechanisms and neuronal/molecular targets remain unknown. We have recently shown that PRR is expressed in VP neurons and that their activation increases neuronal activity. However, the underlying ionic channel mechanisms are undefined. Here, we performed patch-clamp electrophysiology from identified VP neurons in acute hypothalamic slices obtained from enhanced green fluorescent protein-VP transgenic rats. Voltage-clamp recordings showed that PR inhibited the magnitude of A-type K+ current (IA; ~50{\%} at -25 mV), a subthreshold voltage-dependent current that restrains VP firing activity. PR also increased the inactivation rate of IAand shifted the steady-state voltage-dependent inactivation function toward more hyperpolarized membrane potential (~7 mV shift), thus resulting in less channel availability to be activated at any given membrane potential. PR also inhibited a sustained component of IA(“window” current). PR-mediated changes in action potential waveform and increased firing activity were occluded when IA was blocked by 4-aminopyridine. Finally, PR failed to increase superoxide production within the supraoptic nucleus/paraventricular nucleus, and PR excitatory effects persisted in slices treated with the SOD mimetic tempol. Taken together, these experiments indicated that PR excitatory effects on vasopressin neurons involve inhibition of IA, due, in part, to increases in its voltage-dependent inactivation properties. Moreover, our results indicate that PR effects did not involve an increase in oxidative stress. NEW and NOTEWORTHY Here, we demonstrate that prorenin/the prorenin receptor is an important signaling unit for the regulation of vasopressin firing activity and, thus, systemic hormonal release. We identified A-type K+ channels as key molecular targets mediating prorenin stimulation of vasopressin neuronal activity, thus standing as a potential therapeutic target for neurohumoral activation in cardiovascular disease.",
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