C1 neurons of neonatal rats: intrinsic beating properties and alpha 2-adrenergic receptors

1995 ◽  
Vol 269 (6) ◽  
pp. R1356-R1369 ◽  
Author(s):  
Y. W. Li ◽  
D. A. Bayliss ◽  
P. G. Guyenet
Keyword(s):  
Adrenergic Receptors ◽  
Kynurenic Acid ◽  
Lucifer Yellow ◽  
Potassium Conductance ◽  
Ventrolateral Medulla ◽  
Inward Rectification ◽  
Hypotensive Drug ◽  
Outward Currents ◽  
Old Rats ◽  
Inwardly Rectifying

Tyrosine-hydroxylase-immunoreactive (TH-ir) neurons (C1 cells) of the rostral ventrolateral medulla (RVL) control sympathetic tone and may be inhibited by the hypotensive drug clonidine. The present study seeks to describe some of the intrinsic properties of bulbospinal C1 cells and to establish whether they have alpha 2-adrenergic inhibitory "autoreceptors." RVL bulbospinal cells (retrogradely labeled with microbeads) were recorded in thin slices from 3- to 7-day-old rats with patch electrodes containing Lucifer yellow. Forty-two of eighty-nine cells were recovered histologically, and 69% were TH-ir. The properties of TH-ir cells could not be distinguished from those of the other bulbospinal cells. Most cells were spontaneously active (0.5-5 spikes/s). Blockade of fast postsynaptic potentials with kynurenic acid plus bicuculline plus strychnine or with a low-Ca(2+)-high-Mg2+ medium failed to reduce their firing rate. The membrane trajectory consisted of one of two patterns interconvertible by injections of depolarizing or hyperpolarizing current: 1) depolarizing ramps leading to spikes or 2) slow oscillations (tetrodotoxin resistant but absent at hyperpolarized potentials) leading to spikes or repolarization. The cells had Ca(2+)-dependent afterhyperpolarizations, large transient outward currents, and a hyperpolarization-activated inward current activated at potentials less than -65 mV, blocked by CsCl, and presumably responsible for a large inward rectification. Of 27 TH-ir cells, 21 had inhibitory responses to alpha 2-adrenergic agonists. These were blocked by idazoxan (n = 9). alpha 2-Agonists activated an inwardly rectifying potassium conductance (KIR). We confirm that bulbospinal C1 cells have intrinsic pacemaker properties and demonstrate that they have alpha 2-adrenergic receptors (autoreceptors) coupled to KIR channels.

Serotonin and forskolin increase an inwardly rectifying potassium conductance in cultured identified Aplysia neurons

1987 ◽  
Vol 58 (5) ◽  
pp. 909-921 ◽  
Author(s):  
D. P. Lotshaw ◽  
I. B. Levitan
Keyword(s):  
Voltage Clamp ◽  
Potassium Conductance ◽  
Phosphodiesterase Inhibitor ◽  
Identified Neurons ◽  
Inward Rectification ◽  
Current Response ◽  
Aplysia Neurons ◽  
Voltage Dependent ◽  
K Concentration ◽  
Inwardly Rectifying

1. The effect of serotonin (5-HT) and forskolin on an inwardly rectifying K+ conductance (IKR) was studied using voltage-clamp techniques in several identified Aplysia neurons isolated and maintained in primary cell culture. 2. Inward rectification was observed in the current-voltage relationship of the identified neurons R15, R2, B1, and B2 and was predominately due to IKR, as demonstrated by the dependence of inward rectification on the extracellular K+ concentration, instantaneous kinetics of the membrane current response to hyperpolarizing voltage clamp pulses, and voltage-dependent Ba2+ block of the inwardly rectifying current. 3. 5-HT increased IKR conductance between 100 and 400% in the identified neuron R15 in culture and increased IKR conductance approximately 50% in the identified neurons B1, B2, and R2 in culture. The adenylate cyclase activator, forskolin, plus a phosphodiesterase inhibitor, Ro 20-1724, also increased IKR conductance in these neurons. 4. 5-HT and forskolin modulated other ion conductances as well in all of these cultured neurons.

Voltage-Dependent Calcium Currents in Bulbospinal Neurons of Neonatal Rat Rostral Ventrolateral Medulla: Modulation by α2-Adrenergic Receptors

1998 ◽  
Vol 79 (2) ◽  
pp. 583-594 ◽  
Author(s):  
Yu-Wen Li ◽  
Patrice G. Guyenet ◽  
Douglas A. Bayliss
Keyword(s):  
Adrenergic Receptors ◽  
Calcium Current ◽  
Low Voltage ◽  
Lucifer Yellow ◽  
Inhibitory Effect ◽  
Rostral Ventrolateral Medulla ◽  
Calcium Currents ◽  
Neonatal Rat ◽  
Ventrolateral Medulla ◽  
Voltage Dependent

Li, Yu-Wen, Patrice G. Guyenet, and Douglas A. Bayliss. Voltage-dependent calcium currents in bulbospinal neurons of neonatal rat rostral ventrolateral medulla: modulation by α2-adrenergic receptors. J. Neurophysiol. 79: 583–594, 1998. The properties and modulation by norepinephrine (NE) of voltage-dependent calcium currents were studied in bulbospinal neurons ( n = 116) of the rostral ventrolateral medulla (RVLM) using whole cell patch-clamp techniques in neonatal rat brain stem slices. RVLM bulbospinal neurons were identified visually by their location in slices and by the presence of flourescein isothiocyanate-tagged microbeads, which were injected into the spinal cord before the experiment; RVLM neurons were filled with Lucifer yellow during recordings, and the slice was processed for detection of tyrosine hydroxylase immunoreactivity (TH-IR). Thirty-four of 42 recovered cells (81%) were positive for TH-IR, indicating that most recorded cells were C1 neurons. Bulbospinal RVLM neurons expressed a prominent high-voltage–activated (HVA) calcium current, which began to activate at −30 to −40 mV (from a holding potential of −60 or −70 mV), and peaked at ∼0 mV (0.8 ± 0.1 nA;mean ± SE). HVA current comprised predominantly ω-conotoxin GVIA-sensitive, N-type and ω-agatoxin IVA-sensitive, P/Q-type components, with smaller dihydropyridine-sensitive, L-type, and residual current components. Most RVLM bulbospinal neurons ( n = 44/52, including 12/14 histologically identified C1 cells) also expressed low-voltage–activated (LVA) calcium current. LVA current began to activate at ∼−60 mV (from a holding potential of −100 mV) and was nearly completely inactivated at −50 mV with a half-inactivation potential of −70 ± 2 mV. The amplitude of LVA current at −50 mV was 78 ± 24 pA with Ba2+ and 156 ± 38 pA with Ca2+ as a charge carrier. NE inhibited HVA current in most bulbospinal RVLM neurons ( n = 70/77) with an EC50 of 1.2 μM; NE had no effect on LVA current. Calcium current inhibition by NE was mediated by α2-adrenergic receptors (α2-ARs) as the effect was mimicked by the selective α2-AR agonist, UK-14,304, and blocked by idazoxan, an α2-AR antagonist, but unaffected by prazosin and propranolol (α1- and β-AR antagonists, respectively). Most of the NE-sensitive calcium current was N- and P/Q-type. NE-induced inhibition of calcium current evoked by action potential waveforms (APWs) was significantly larger than that evoked by depolarizing steps (34 ± 2.5 vs. 23 ± 2.7%; P < 0.05). Although inhibition of calcium current was voltage dependent and partially relieved by strong depolarizations, when calcium currents were evoked with a 10-Hz train of APWs as a voltage command, the inhibitory effect of NE was maintained throughout the train. In conclusion, bulbospinal RVLM neurons, including C1 cells, express multiple types of calcium currents. Inhibition of HVA calcium current by NE may modulate input-output relationships and release of transmitters from C1 cells.

Inward rectification in rat nucleus accumbens neurons

1989 ◽  
Vol 62 (6) ◽  
pp. 1280-1286 ◽  
Author(s):  
N. Uchimura ◽  
E. Cherubini ◽  
R. A. North
Keyword(s):  
Steady State ◽  
Nucleus Accumbens ◽  
Time Course ◽  
Potassium Conductance ◽  
Resting Potential ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Potential Range ◽  
Inward Current ◽  
Rat Nucleus Accumbens

1. Intracellular recordings were made from neurons in slices cut from the rat nucleus accumbens septi. Membrane currents were measured with a single-electrode voltage-clamp amplifier in the potential range -50 to -140 mV. 2. In control conditions (2.5 mM potassium), the resting membrane potential of the neurons was -83.4 +/- 1.1 (SE) mV (n = 157). Steady state membrane conductance was voltage dependent, being 34.8 +/- 1.7 nS (n = 25) at -100 mV and 8.0 +/- 0.7 nS (n = 25) at -60 mV. 3. Barium (1 microM) markedly reduced the inward rectification and caused a small inward current (40.6 +/- 8.7 pA, n = 8) at the resting potential. These effects became larger with higher barium concentrations, and, in 100 microM barium, the current-voltage relation was straight. 4. The block of the inward current by barium (at -130 mV) occurred with an exponential time course; the time constant was approximately 1 s at 1 microM barium and less than 90 ms with 100 microM. Strontium had effects similar to those of barium, but 1000-fold higher concentrations were required. Cesium chloride (2 mM) and rubidium chloride (2 mM) also blocked the inward rectification; their action reached steady state within 50 ms. 5. It is concluded that the nucleus accumbens neurons have a potassium conductance with many features of a typical inward rectifier and that this contributes to the potassium conductance at the resting potential.

scholarly journals Decrease in an Inwardly Rectifying Potassium Conductance in Mouse Mammary Secretory Cells after Forced Weaning

PLoS ONE ◽  
2015 ◽  
Vol 10 (10) ◽  
pp. e0141131 ◽  
Author(s):  
Akihiro Kamikawa ◽  
Shota Sugimoto ◽  
Osamu Ichii ◽  
Daisuke Kondoh
Keyword(s):  
Potassium Conductance ◽  
Secretory Cells ◽  
Inwardly Rectifying

Outward currents in normal and hypertrophied feline ventricular myocytes

1989 ◽  
Vol 256 (5) ◽  
pp. H1450-H1461 ◽  
Author(s):  
R. B. Kleiman ◽  
S. R. Houser
Keyword(s):  
Time Course ◽  
Ventricular Myocytes ◽  
Pressure Overload ◽  
Negative Slope ◽  
Inward Rectification ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
K Current ◽  
Prolongation Of Action Potential ◽  
The Right

The properties of the inward rectifier K current (IK1) and the delayed rectifier K current (IK) were studied in single feline myocytes isolated from the right ventricle of normal cats and cats with experimentally induced right ventricular hypertrophy (RVH). IK1 demonstrated time-dependent decay during hyperpolarizations and showed inward rectification with a prominent negative-slope region between -30 and -10 mV. Both IK1 and IK was carried primarily by K ions. The activation of IK during depolarizations followed a monoexponential time course, whereas the deactivation of IK tail currents was either mono- or biexponential depending on the repolarization potential. IK showed marked rectification at positive potentials. A comparison of these currents in normal and hypertrophy myocytes revealed that in RVH the magnitude of IK1 is increased, whereas the magnitude of IK is decreased. IK showed steeper rectification, had slower activation, and had more rapid deactivation in RVH. These abnormalities of the IK may contribute to the prolongation of action potential duration, which characterizes pressure-overload cardiac hypertrophy.

Inhibition of a Fast Inwardly Rectifying Potassium Conductance by Barbiturates

1996 ◽  
Vol 82 (6) ◽  
pp. 1242-1246 ◽  
Author(s):  
Simon J. Gibbons ◽  
Ramon Nunez-Hernandez ◽  
Ghislaine Maze ◽  
Neil L. Harrison
Keyword(s):  
Potassium Conductance ◽  
Inwardly Rectifying

Inwardly Rectifying and Ca2+-Permeable AMPA-Type Glutamate Receptor Channels in Rat Neocortical Neurons

1997 ◽  
Vol 78 (5) ◽  
pp. 2592-2601 ◽  
Author(s):  
Shun-Ichi Itazawa ◽  
Tadashi Isa ◽  
Seiji Ozawa
Keyword(s):  
Glutamate Receptor ◽  
Ampa Receptor ◽  
Inward Rectification ◽  
Type I ◽  
Type Ii ◽  
Neocortical Neurons ◽  
Rat Neocortex ◽  
Type I Neuron ◽  
Inwardly Rectifying ◽  
Ampa Receptor Channels

Itazawa, Shun-Ichi, Tadashi Isa, and Seiji Ozawa. Inwardly rectifying and Ca2+-permeable AMPA-type glutamate receptor channels in rat neocortical neurons. J. Neurophysiol. 78: 2592–2605, 1997. Current-voltage ( I-V) relations and Ca2+ permeability of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)type glutamate receptor channels were investigated in neurons of rat neocortex by using the whole cell patch-clamp technique in brain slices. To activate AMPA receptor channels, kainate was used as a nondesensitizing agonist. A patch pipette was filled with solution containing 100 μM spermine to maintain the inward rectification of Ca2+-permeable AMPA receptor channels. Three types of responses to kainate were observed: type I response with outwardly rectifying I-V relation, type II response with I-V relation of marked inward rectification, and intermediate response with I-V relation of weaker inward rectification. Neurons with type I, type II and intermediate I-V relations were referred to as type I, type II, and intermediate neurons, respectively. Of a total of 223 recorded cells, 90 (40.4%) were type I, 129 (57.8%) intermediate, and 4 (1.8%) type II neurons. Properties of AMPA receptor channels were examined in the former two types of neurons. The value of PCa:PCs, the ratio of the permeability coefficients of Ca2+ and Cs+, was estimated from the reversal potentials of kainate responses in the outside-out patches bathed in Na+-free solution containing 100 mM Ca2+ according to the constant-field equation. They ranged from 0.05 to 0.10 (0.08 ± 0.02, mean ± SD, n = 8) for type I neurons and from 0.14 to 1.29 (0.60 ± 0.37, n = 11) for the intermediate neurons. There was a close correlation between the inward rectification and the Ca2+ permeability in AMPA receptor channels in these neurons. Intermediate neurons stained with biocytin were nonpyramidal cells with ellipsoidal-shaped somata. Type I neurons had either triangular- or ellipsoidal-shaped somata. Excitatory postsynaptic currents (EPSCs) recorded in both type I and intermediate neurons had 6-cyano-7-nitroquinoxaline-2,3-dione-sensitive fast and d−2-amino-5-phosphonovalerate-sensitiveslow components. The I-V relation of the fast component exhibited inward rectification in the intermediate neuron, whereas that in the type I neuron showed slight outward rectification. The fast component of EPSCs in the intermediate neuron was suppressed more prominently (to 56 ± 15% of the control, n = 12) than that in the type I neuron (to 78 ± 6% of the control, n = 6) by bath application of 1 mM spermine. These results indicate that inwardly rectifying and Ca2+-permeable AMPA receptor channels are expressed in a population of neurons of rat neocortex and are involved in excitatory synaptic transmission.

Differential cardiorespiratory control elicited by activation of ventral medullary sites in mice

2000 ◽  
Vol 89 (2) ◽  
pp. 437-444 ◽  
Author(s):  
F. P. Tolentino-Silva ◽  
M. A. Haxhiu ◽  
P. Ernsberger ◽  
S. Waldbaum ◽  
I. A. Dreshaj
Keyword(s):  
Blood Pressure ◽  
Adrenergic Receptors ◽  
Excitatory Amino Acid ◽  
Signal Transduction Pathway ◽  
Ventrolateral Medulla ◽  
Respiratory Drive ◽  
Breathing Frequency ◽  
Cardiorespiratory Control ◽  
Blood Pressure Responses ◽  
Stimulation Of

We studied the respiratory and blood pressure responses to chemical stimulation of two regions of the ventral brainstem in mice: the rostral and caudal ventrolateral medulla (RVLM and CVLM, respectively). Stimulation of the RVLM by microinjections of the excitatory amino acid l-glutamate induced increases in diaphragm activity and breathing frequency, elevation of blood pressure (BP), and a slight increase in heart rate (HR). However, activation of the CVLM induced a decrease in breathing frequency, mainly due to prolongation of expiratory time (Te), and hypotension associated with a slight slowing of HR. Because adrenergic mechanisms are known to participate in the control of respiratory timing, we examined the role of α2-adrenergic receptors in the RVLM region in mediating these inhibitory effects. The findings demonstrated that blockade of the α2-adrenergic receptors within the RVLM by prior microinjection of SKF-86466 (an α2-adrenergic receptor blocker) significantly reduced changes in Te induced by CVLM stimulation but had little effect on BP responses. These results indicate that, in mice, activation of the RVLM increases respiratory drive associated with an elevation of BP, but stimulation of CVLM induces prolongation of Te via an α2-adrenergic signal transduction pathway.

Calcium-modulated inward rectification of a calcium-activated potassium channel in neurons

1994 ◽  
Vol 72 (6) ◽  
pp. 3023-3025 ◽  
Author(s):  
J. Kang ◽  
C. Sumners ◽  
P. Posner
Keyword(s):  
Patch Clamp ◽  
Brain Stem ◽  
Inward Rectification ◽  
K Channel ◽  
Minor Effect ◽  
Bath Solution ◽  
Old Rats ◽  
A Minor ◽  
Calcium Activated Potassium Channel ◽  
Inside Out

1. Inward rectification of a calcium-activated K+ channel in neurons cultured from the hypothalamus and brain stem of 1-day-old rats was studied by using patch-clamp techniques. A big conductance calcium-activated K+ channel with a slow gating rate was observed in inside-out patches. With symmetrical K+ across patches, inward conductance of this calcium-activated K+ channel was 216 +/- 14 (SE) pS (n = 4 patches), which changed little as different [Ca2+] was included in the bath solution. Outward conductance of this calcium-activated K+ channel was regulated by [Ca2+] in the bath solution and was 74 +/- 15 pS with 500 microM Ca2+. The higher level of Ca2+ on the intracellular side of the membrane caused the larger degree of rectification. Mg2+ only had a minor effect on rectification of this calcium-activated K+ channel.

Effect of substance P on C1 and other bulbospinal cells of the RVLM in neonatal rats

1997 ◽  
Vol 273 (2) ◽  
pp. R805-R813 ◽  
Author(s):  
Y. W. Li ◽  
P. G. Guyenet
Keyword(s):  
Substance P ◽  
Discharge Rate ◽  
Potassium Conductance ◽  
Input Resistance ◽  
Ventrolateral Medulla ◽  
Equilibrium Potential ◽  
Neonatal Rats ◽  
Spontaneous Firing Rate ◽  
Sympathetic Vasomotor Tone

Sixty-two bulbospinal neurons were recorded in the rostral ventrolateral medulla (RVLM) of neonatal rats using patch electrodes. Sixty-one percent of the recorded neurons identified by histology contained tyrosine-hydroxylase (C1 cells). Substance P increased the spontaneous firing rate of all recorded cells but had no effect on spike configuration. The peptide depolarized neurons that were silenced by injection of hyperpolarizing current and increased their input resistance. All cells (n = 12) were activated by a neurokinin (NK)1 receptor agonist but most were unaffected by an NK2- or an NK2-selective compound. In voltage clamp, substance P produced a current that was linearly related to the membrane voltage. This current reversed polarity close to the potassium equilibrium potential in 11 of 23 cells. It reversed at more hyperpolarized potentials or not at all in the rest of the cells. In conclusion, substance P upregulates the intrinsic discharge rate of C1 and other putative sympathoexcitatory cells in neonatal rats. This effect is mediated via NK1 receptors. The depolarization is mediated by a reduction in resting potassium conductance and possibly by an additional cationic conductance. These results support the possibility that substance P could play a role "in vivo" in setting the basal level of discharge of the vasomotor cells of RVLM and therefore in regulating sympathetic vasomotor tone.

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