Angiotensin II excites paraventricular nucleus neurons that innervate the rostral ventrolateral medulla: An in vitro patch-clamp study in brain slices

Matthew J. Cato, Glenn M Toney

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Abstract

Neurons of the hypothalamic paraventricular nucleus (PVN) are key controllers of sympathetic nerve activity and receive input from angiotensin II (ANG II)-containing neurons in the forebrain. This study determined the effect of ANG II on PVN neurons that innervate in the rostral ventrolateral medulla (RVLM) - a brain stem site critical for maintaining sympathetic outflow and arterial pressure. Using an in vitro brain slice preparation, whole cell patch-clamp recordings were made from PVN neurons retrogradely labeled from the ipsilateral RVLM of rats. Of 71 neurons tested, 62 (87%) responded to ANG II. In current-clamp mode, bath-applied ANG II (2 μM) significantly (P < 0.05) depolarized membrane potential from -58.5 ± 2.5 to -54.5 ± 2.0 mV and increased the frequency of action potential discharge from 0.7 ± 0.3 to 2.8 ± 0.8 Hz (n = 4). Local application of ANG II by low-pressure ejection from a glass pipette (2 pmol, 0.4 nl, 5 s) also elicited rapid and reproducible excitation in 17 of 20 cells. In this group, membrane potential depolarization averaged 21.5 ± 4.1 mV, and spike activity increased from 0.7 ± 0.4 to 21.3 ± 3.3 Hz. In voltage-clamp mode, 41 of 47 neurons responded to pressure-ejected ANG II with a dose-dependent inward current that averaged -54.7 ± 3.9 pA at a maximally effective dose of 2.0 pmol. Blockade of ANG II AT1 receptors significantly reduced discharge (P < 0.001, n= 5), depolarization (P < 0.05, n = 3), and inward current (P < 0.01, n= 11) responses to locally applied ANG II. In six of six cells tested, membrane input conductance increased (P < 0.001) during local application of ANG II (2 pmol), suggesting influx of cations. The ANG II current reversed polarity at +2.2 ± 2.2 mV (n = 9) and was blocked (P < 0.01) by bath perfusion with gadolinium (Gd3+, 100 μM, n = 8), suggesting that ANG II activates membrane channels that are nonselectively permeable to cations. These findings indicate that ANGII excites PVN neurons that innervate the ipsilateral RVLM by a mechanism that depends on activation of AT1 receptors and gating of one or more classes of ion channels that result in a mixed cation current.

Original languageEnglish (US)
Pages (from-to)403-413
Number of pages11
JournalJournal of Neurophysiology
Volume93
Issue number1
DOIs
StatePublished - Jan 2005

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Paraventricular Hypothalamic Nucleus
Angiotensin II
Neurons
Brain
Cations
Baths
Ion Channels
Membrane Potentials
In Vitro Techniques
Pressure
Angiotensin Type 1 Receptor
Angiotensin Receptors
Gadolinium
Prosencephalon
Action Potentials
Brain Stem
Glass
Arterial Pressure
Perfusion
Cell Membrane

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

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title = "Angiotensin II excites paraventricular nucleus neurons that innervate the rostral ventrolateral medulla: An in vitro patch-clamp study in brain slices",
abstract = "Neurons of the hypothalamic paraventricular nucleus (PVN) are key controllers of sympathetic nerve activity and receive input from angiotensin II (ANG II)-containing neurons in the forebrain. This study determined the effect of ANG II on PVN neurons that innervate in the rostral ventrolateral medulla (RVLM) - a brain stem site critical for maintaining sympathetic outflow and arterial pressure. Using an in vitro brain slice preparation, whole cell patch-clamp recordings were made from PVN neurons retrogradely labeled from the ipsilateral RVLM of rats. Of 71 neurons tested, 62 (87{\%}) responded to ANG II. In current-clamp mode, bath-applied ANG II (2 μM) significantly (P < 0.05) depolarized membrane potential from -58.5 ± 2.5 to -54.5 ± 2.0 mV and increased the frequency of action potential discharge from 0.7 ± 0.3 to 2.8 ± 0.8 Hz (n = 4). Local application of ANG II by low-pressure ejection from a glass pipette (2 pmol, 0.4 nl, 5 s) also elicited rapid and reproducible excitation in 17 of 20 cells. In this group, membrane potential depolarization averaged 21.5 ± 4.1 mV, and spike activity increased from 0.7 ± 0.4 to 21.3 ± 3.3 Hz. In voltage-clamp mode, 41 of 47 neurons responded to pressure-ejected ANG II with a dose-dependent inward current that averaged -54.7 ± 3.9 pA at a maximally effective dose of 2.0 pmol. Blockade of ANG II AT1 receptors significantly reduced discharge (P < 0.001, n= 5), depolarization (P < 0.05, n = 3), and inward current (P < 0.01, n= 11) responses to locally applied ANG II. In six of six cells tested, membrane input conductance increased (P < 0.001) during local application of ANG II (2 pmol), suggesting influx of cations. The ANG II current reversed polarity at +2.2 ± 2.2 mV (n = 9) and was blocked (P < 0.01) by bath perfusion with gadolinium (Gd3+, 100 μM, n = 8), suggesting that ANG II activates membrane channels that are nonselectively permeable to cations. These findings indicate that ANGII excites PVN neurons that innervate the ipsilateral RVLM by a mechanism that depends on activation of AT1 receptors and gating of one or more classes of ion channels that result in a mixed cation current.",
author = "Cato, {Matthew J.} and Toney, {Glenn M}",
year = "2005",
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T1 - Angiotensin II excites paraventricular nucleus neurons that innervate the rostral ventrolateral medulla

T2 - An in vitro patch-clamp study in brain slices

AU - Cato, Matthew J.

AU - Toney, Glenn M

PY - 2005/1

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N2 - Neurons of the hypothalamic paraventricular nucleus (PVN) are key controllers of sympathetic nerve activity and receive input from angiotensin II (ANG II)-containing neurons in the forebrain. This study determined the effect of ANG II on PVN neurons that innervate in the rostral ventrolateral medulla (RVLM) - a brain stem site critical for maintaining sympathetic outflow and arterial pressure. Using an in vitro brain slice preparation, whole cell patch-clamp recordings were made from PVN neurons retrogradely labeled from the ipsilateral RVLM of rats. Of 71 neurons tested, 62 (87%) responded to ANG II. In current-clamp mode, bath-applied ANG II (2 μM) significantly (P < 0.05) depolarized membrane potential from -58.5 ± 2.5 to -54.5 ± 2.0 mV and increased the frequency of action potential discharge from 0.7 ± 0.3 to 2.8 ± 0.8 Hz (n = 4). Local application of ANG II by low-pressure ejection from a glass pipette (2 pmol, 0.4 nl, 5 s) also elicited rapid and reproducible excitation in 17 of 20 cells. In this group, membrane potential depolarization averaged 21.5 ± 4.1 mV, and spike activity increased from 0.7 ± 0.4 to 21.3 ± 3.3 Hz. In voltage-clamp mode, 41 of 47 neurons responded to pressure-ejected ANG II with a dose-dependent inward current that averaged -54.7 ± 3.9 pA at a maximally effective dose of 2.0 pmol. Blockade of ANG II AT1 receptors significantly reduced discharge (P < 0.001, n= 5), depolarization (P < 0.05, n = 3), and inward current (P < 0.01, n= 11) responses to locally applied ANG II. In six of six cells tested, membrane input conductance increased (P < 0.001) during local application of ANG II (2 pmol), suggesting influx of cations. The ANG II current reversed polarity at +2.2 ± 2.2 mV (n = 9) and was blocked (P < 0.01) by bath perfusion with gadolinium (Gd3+, 100 μM, n = 8), suggesting that ANG II activates membrane channels that are nonselectively permeable to cations. These findings indicate that ANGII excites PVN neurons that innervate the ipsilateral RVLM by a mechanism that depends on activation of AT1 receptors and gating of one or more classes of ion channels that result in a mixed cation current.

AB - Neurons of the hypothalamic paraventricular nucleus (PVN) are key controllers of sympathetic nerve activity and receive input from angiotensin II (ANG II)-containing neurons in the forebrain. This study determined the effect of ANG II on PVN neurons that innervate in the rostral ventrolateral medulla (RVLM) - a brain stem site critical for maintaining sympathetic outflow and arterial pressure. Using an in vitro brain slice preparation, whole cell patch-clamp recordings were made from PVN neurons retrogradely labeled from the ipsilateral RVLM of rats. Of 71 neurons tested, 62 (87%) responded to ANG II. In current-clamp mode, bath-applied ANG II (2 μM) significantly (P < 0.05) depolarized membrane potential from -58.5 ± 2.5 to -54.5 ± 2.0 mV and increased the frequency of action potential discharge from 0.7 ± 0.3 to 2.8 ± 0.8 Hz (n = 4). Local application of ANG II by low-pressure ejection from a glass pipette (2 pmol, 0.4 nl, 5 s) also elicited rapid and reproducible excitation in 17 of 20 cells. In this group, membrane potential depolarization averaged 21.5 ± 4.1 mV, and spike activity increased from 0.7 ± 0.4 to 21.3 ± 3.3 Hz. In voltage-clamp mode, 41 of 47 neurons responded to pressure-ejected ANG II with a dose-dependent inward current that averaged -54.7 ± 3.9 pA at a maximally effective dose of 2.0 pmol. Blockade of ANG II AT1 receptors significantly reduced discharge (P < 0.001, n= 5), depolarization (P < 0.05, n = 3), and inward current (P < 0.01, n= 11) responses to locally applied ANG II. In six of six cells tested, membrane input conductance increased (P < 0.001) during local application of ANG II (2 pmol), suggesting influx of cations. The ANG II current reversed polarity at +2.2 ± 2.2 mV (n = 9) and was blocked (P < 0.01) by bath perfusion with gadolinium (Gd3+, 100 μM, n = 8), suggesting that ANG II activates membrane channels that are nonselectively permeable to cations. These findings indicate that ANGII excites PVN neurons that innervate the ipsilateral RVLM by a mechanism that depends on activation of AT1 receptors and gating of one or more classes of ion channels that result in a mixed cation current.

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