D2S, D2L, D3, and D4 dopamine receptors couple to a voltage-dependent potassium current in N18TG2 � mesencephalon hybrid cell (MES-23.5) via distinct G proteins

Synapse ◽  
1999 ◽  
Vol 31 (2) ◽  
pp. 108-118 ◽  
Author(s):  
Li-Xin Liu ◽  
Loyd H. Burgess ◽  
Antonia M. Gonzalez ◽  
David R. Sibley ◽  
Louis A. Chiodo
Keyword(s):  
Dopamine Receptors ◽  
G Proteins ◽  
Potassium Current ◽  
Hybrid Cell ◽  
Voltage Dependent

scholarly journals Modulation of High-Voltage Activated Ca2+ Channels in the Rat Periaqueductal Gray Neurons by μ-Type Opioid Agonist

1997 ◽  
Vol 77 (3) ◽  
pp. 1418-1424 ◽  
Author(s):  
Chang-Ju Kim ◽  
Jeong-Seop Rhee ◽  
Norio Akaike
Keyword(s):  
G Proteins ◽  
Opioid Receptor ◽  
High Voltage ◽  
Inhibitory Effect ◽  
Periaqueductal Gray ◽  
Dependent Manner ◽  
Opioid Agonist ◽  
Voltage Clamp Condition ◽  
Voltage Dependent ◽  
Clamp Condition

Kim, Chang-Ju, Jeong-Seop Rhee, and Norio Akaike. Modulation of high-voltage activated Ca2+ channels in the rat periaqueductal gray neurons by μ-type opioid agonist. J. Neurophysiol. 77: 1418–1424, 1997. The effect of μ-type opioid receptor agonist, D-Ala2,N-MePhe4,Gly5-ol-enkephalin (DAMGO), on high-voltage-activated (HVA) Ca2+ channels in the dissociated rat periaqueductal gray (PAG) neurons was investigated by the use of nystatin-perforated patch recording mode under voltage-clamp condition. Among 118 PAG neurons tested, the HVA Ca2+ channels of 38 neurons (32%) were inhibited by DAMGO (DAMGO-sensitive cells), and the other 80 neurons (68%) were not affected by DAMGO (DAMGO-insensitive cells). The N-, P-, L-, Q-, and R-type Ca2+ channel components in DAMGO-insensitive cells shared 26.9, 37.1, 22.3, 7.9, and 5.8%, respectively, of the total Ca2+ channel current. The channel components of DAMGO-sensitive cells were 45.6, 25.7, 21.7, 4.6, and 2.4%, respectively. The HVA Ca2+ current of DAMGO-sensitive neurons was inhibited by DAMGO in a concentration-, time-, and voltage-dependent manner. Application of ω-conotoxin-GVIA occluded the inhibitory effect of DAMGO ∼70%. So, HVA Ca2+ channels inhibited by DAMGO were mainly the N-type Ca2+ channels. The inhibitory effect of DAMGO on HVA Ca2+ channels was prevented almost completely by the pretreatment of pertussis toxin (PTX) for 8–10 h, suggesting that DAMGO modulation on N-type Ca2+ channels in rat PAG neurons is mediated by PTX-sensitive G proteins. These results indicate that μ-type opioid receptor modulates N-type HVA Ca2+ channels via PTX-sensitive G proteins in PAG neurons of rats.

scholarly journals KCNE1 and KCNE3 modulate KCNQ1 channels by affecting different gating transitions

2017 ◽  
Vol 114 (35) ◽  
pp. E7367-E7376 ◽  
Author(s):  
Rene Barro-Soria ◽  
Rosamary Ramentol ◽  
Sara I. Liin ◽  
Marta E. Perez ◽  
Robert S. Kass ◽  
...  
Keyword(s):  
Action Potentials ◽  
Potassium Current ◽  
Voltage Sensor ◽  
Α Subunit ◽  
Voltage Range ◽  
Gate Opening ◽  
Cardiac Action ◽  
Repolarization Phase ◽  
Voltage Dependent ◽  
Salt Secretion

KCNE β-subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with the α-subunit KCNQ1 to generate the slowly activating, voltage-dependent potassium current (IKs) in the heart that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach, and kidney, KCNE3 coassembles with KCNQ1 to form K+ channels that are voltage-independent K+ channels in the physiological voltage range and important for controlling water and salt secretion and absorption. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by mutations or phosphatidylinositol 4,5-bisphosphate depletion, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 affects the S4 movement and only affects the gate in KCNQ1 if an intact S4-to-gate coupling is present. Further, we show that a triple mutation in the middle of the transmembrane (TM) segment of KCNE3 introduces KCNE1-like effects on the second S4 movement and the gate. In addition, we show that differences in two residues at the external end of the KCNE TM segments underlie differences in the effects of the different KCNEs on the first S4 movement and the voltage sensor-to-gate coupling.

Inhibition of Ca2+-induced calcitonin secretion by somatostatin: Roles of voltage dependent Ca2+ channels and G-proteins

1992 ◽  
Vol 4 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Hans Scherüble ◽  
Jürgen Hescheler ◽  
Günter Schultz ◽  
Dietrich Kliemann ◽  
Angela Zink ◽  
...  
Keyword(s):  
G Proteins ◽  
Voltage Dependent ◽  
Calcitonin Secretion ◽  
Ca2 Channels

Norepinephrine Inhibits a Toxin Resistant Ca2+ Current in Carotid Body Glomus Cells: Evidence for a Direct G Protein Mechanism

1999 ◽  
Vol 81 (1) ◽  
pp. 225-233 ◽  
Author(s):  
Jeffrey L. Overholt ◽  
Nanduri R. Prabhakar
Keyword(s):  
Receptor Antagonist ◽  
G Protein ◽  
G Proteins ◽  
Carotid Body ◽  
Adrenergic Receptor ◽  
Subunit Interaction ◽  
Whole Cell ◽  
Glomus Cells ◽  
Voltage Dependent ◽  
Carotid Body Glomus Cells

Overholt, Jeffrey L. and Nanduri R. Prabhakar. Norepinephrine inhibits a toxin resistant Ca2+ current in carotid body glomus cells: evidence for a direct G protein mechanism. J. Neurophysiol. 81: 225–233, 1999. Previous studies have demonstrated that endogenous norepinephrine (NE) inhibits carotid body (CB) sensory discharge, and the cellular actions of NE have been associated with inhibition of Ca2+ current in glomus cells. The purpose of the present study was to elucidate the characteristics and mechanism of NE inhibition of whole cell Ca2+ current isolated from rabbit CB glomus cells and to determine the type(s) of Ca2+ channel involved. NE (10 μM) inhibited 24 ± 2% (SE) of the macroscopic Ca2+ current measured at the end of a 25 ms pulse to 0 mV and slowed activation of the current. The α2 adrenergic receptor antagonist, SK&F 86466, attenuated these effects. Inhibition by NE was fast and voltage-dependent i.e., maximal at −10 mV and then diminished with stronger depolarizations. This is characteristic of G protein βγ subunit interaction with the α1 subunit of certain Ca2+ channels, which can be relieved by depolarizing steps. A depolarizing step (30 ms to +80 mV) significantly increased (14 ± 1%) current in the presence of NE, whereas it had no effect before application of NE (1 ± 1%). To further test for the involvement of G proteins, NE was applied to cells where intracellular GTP was replaced by GDP-βS. NE had little or no effect on Ca2+ current in cells dialyzed with GDP-βS. To determine whether NE was inhibiting N- and/or P/Q-type channels, we applied NE in the presence of ω-conotoxin MVIIC (MVIIC). In the presence of 2.5 μM MVIIC, NE was equally potent at inhibiting the Ca2+ current (23 ± 4% vs. 23 ± 4% in control), suggesting that NE was not exclusively inhibiting N- or P/Q-type channels. NE was also equally potent (30 ± 2% vs. 26 ± 4% in control) at inhibiting the Ca2+ current in the presence of 2 μM nisoldipine, suggesting that NE was not inhibiting L-type channels. Further, NE inhibited a significantly larger proportion (47 ± 6%) of the resistant Ca2+ current remaining in the presence of NISO and MVIIC. These results suggest that NE inhibition of Ca2+ current in rabbit CB glomus cells is mediated in most part by effects on the resistant, non L-, N-, or P/Q-type channel and involves a direct G protein βγ interaction with this channel.

Two temporally overlapping "delayed-rectifiers" determine the voltage-dependent potassium current phenotype in cultured hippocampal interneurons

1996 ◽  
Vol 76 (3) ◽  
pp. 1477-1490 ◽  
Author(s):  
A. Chikwendu ◽  
C. J. McBain
Keyword(s):  
Potassium Current ◽  
Critical Role ◽  
Relative Proportion ◽  
Minor Component ◽  
Transient Current ◽  
Stratum Radiatum ◽  
Delayed Rectifier ◽  
Gamma Aminobutyric Acid ◽  
Current Component ◽  
Voltage Dependent

1. Whole cell voltage-clamp recordings were used to characterize the calcium-independent "delayed-rectifier" potassium currents of gamma-aminobutyric acid (GABA)-positive stratum radiatum-lacunosum-moleculare (st. L-M) interneurons in primary culture derived from neonate rats [postnatal day 5-7 (P5-P7)]. 2. Two distinct current phenotypes were observed, which we termed "sustained" and "slowly inactivating." Despite possessing similar voltage-dependent activation properties, current differed in their time-dependent inactivation properties and their kinetics of activation and deactivation. The phenotypes of the observed currents did not change during the time in vitro. The total current phenotype observed in any cell likely resulted from the temporal overlap of the two current components expressed in different relative proportions. 3. Externally applied 4-aminopyridine (4-AP) selectively blocked the slowly inactivating current component, by a use-dependent, but voltage-independent mechanism, suggesting that channel activation is required for 4-AP to interact with its binding site. In contrast, the sustained current component was unaffected by 4-AP. 4. Both the slowly inactivating and sustained current phenotypes were sensitive to externally applied tetraethylammonium (TEA). The IC50 of block by TEA was lower in cells expressing predominantly the sustained current components. 5. Currents recorded in the presence of internally applied TEA were of a slowly inactivating phenotype, suggesting that [TEA]i preferentially blocked the sustained current component. 6. When test pulses were preceded by a prepulse to -100 mV, a transient A-type current component was observed, but in contrast to pyramidal neurons and other interneuron types, this transient current contributed only a minor component to the total initial peak current. 7. In conclusion, two distinct, temporally overlapping potassium current phenotypes were observed on st. L-M interneurons. The overall phenotype was determined by the relative proportion of each current component. The absence of a prominent transient current suggests that the two delayed-rectifier currents play a critical role in determining the firing characteristics of these interneurons.

scholarly journals Specific Involvement of Gonadal Hormones in the Functional Maturation of Growth Hormone Releasing Hormone (GHRH) Neurons

Endocrinology ◽  
2010 ◽  
Vol 151 (12) ◽  
pp. 5762-5774 ◽  
Author(s):  
Laurie-Anne Gouty-Colomer ◽  
Pierre-François Méry ◽  
Emilie Storme ◽  
Elodie Gavois ◽  
Iain C. Robinson ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Postnatal Development ◽  
Potassium Current ◽  
Hormonal Treatment ◽  
Gonadal Hormones ◽  
Detailed Knowledge ◽  
Releasing Hormone ◽  
Electrophysiological Properties ◽  
Gh Secretion ◽  
Voltage Dependent

Growth hormone (GH) is the key hormone involved in the regulation of growth and metabolism, two functions that are highly modulated during infancy. GH secretion, controlled mainly by GH releasing hormone (GHRH), has a characteristic pattern during postnatal development that results in peaks of blood concentration at birth and puberty. A detailed knowledge of the electrophysiology of the GHRH neurons is necessary to understand the mechanisms regulating postnatal GH secretion. Here, we describe the unique postnatal development of the electrophysiological properties of GHRH neurons and their regulation by gonadal hormones. Using GHRH-eGFP mice, we demonstrate that already at birth, GHRH neurons receive numerous synaptic inputs and fire large and fast action potentials (APs), consistent with effective GH secretion. Concomitant with the GH secretion peak occurring at puberty, these neurons display modifications of synaptic input properties, decrease in AP duration, and increase in a transient voltage-dependant potassium current. Furthermore, the modulation of both the AP duration and voltage-dependent potassium current are specifically controlled by gonadal hormones because gonadectomy prevented the maturation of these active properties and hormonal treatment restored it. Thus, GHRH neurons undergo specific developmental modulations of their electrical properties over the first six postnatal weeks, in accordance with hormonal demand. Our results highlight the importance of the interaction between the somatotrope and gonadotrope axes during the establishment of adapted neuroendocrine functions.

The monomeric G proteins AGS1 and Rhes selectively influence Gαi-dependent signaling to modulate N-type (CaV2.2) calcium channels

2008 ◽  
Vol 295 (5) ◽  
pp. C1417-C1426 ◽  
Author(s):  
Ashish Thapliyal ◽  
Roger A. Bannister ◽  
Christopher Hanks ◽  
Brett A. Adams
Keyword(s):  
G Proteins ◽  
Pertussis Toxin ◽  
Hek293 Cells ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Heterotrimeric G Proteins ◽  
Physiological Conditions ◽  
Channel Inhibition ◽  
Voltage Dependent ◽  
Current Densities

Activator of G protein Signaling 1 (AGS1) and Ras homologue enriched in striatum (Rhes) define a new group of Ras-like monomeric G proteins whose signaling properties and physiological roles are just beginning to be understood. Previous results suggest that AGS1 and Rhes exhibit distinct preferences for heterotrimeric G proteins, with AGS1 selectively influencing Gαi and Rhes selectively influencing Gαs. Here, we demonstrate that AGS1 and Rhes trigger nearly identical modulation of N-type Ca2+ channels (CaV2.2) by selectively altering Gαi-dependent signaling. Whole-cell currents were recorded from HEK293 cells expressing CaV2.2 and Gαi- or Gαs-coupled receptors. AGS1 and Rhes reduced basal current densities and triggered tonic voltage-dependent (VD) inhibition of CaV2.2. Additionally, each protein attenuated agonist-initiated channel inhibition through Gαi-coupled receptors without reducing channel inhibition through a Gαs-coupled receptor. The above effects of AGS1 and Rhes were blocked by pertussis toxin (PTX) or by expression of a Gβγ-sequestering peptide (masGRK3ct). Transfection with HRas, KRas2, Rap1A-G12V, Rap2B, Rheb2, or Gem failed to duplicate the effects of AGS1 and Rhes on CaV2.2. Our data provide the first demonstration that AGS1 and Rhes exhibit similar if not identical signaling properties since both trigger tonic Gβγ signaling and both attenuate receptor-initiated signaling by the Gβγ subunits of PTX-sensitive G proteins. These results are consistent with the possibility that AGS1 and Rhes modulate Ca2+ influx through CaV2.2 channels under more physiological conditions and thereby influence Ca2+-dependent events such as neurosecretion.

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