scholarly journals On the Contribution of the First Transmembrane Domain to Whole-Cell Current through an ATP-Gated Ionotropic P2X Receptor

2001 ◽  
Vol 21 (16) ◽  
pp. 5885-5892 ◽  
Author(s):  
William R. Haines ◽  
Mark M. Voigt ◽  
Keisuke Migita ◽  
Gonzalo E. Torres ◽  
Terrance M. Egan
Keyword(s):  
Transmembrane Domain ◽  
P2x Receptor ◽  
Whole Cell ◽  
Cell Current ◽  
Whole Cell Current

scholarly journals Modulation of inhibitory and excitatory fast neurotransmission in the rat CNS by heavy water (D2O)

2015 ◽  
Vol 114 (2) ◽  
pp. 1109-1118 ◽  
Author(s):  
Masahito Wakita ◽  
Naoki Kotani ◽  
Kiyomitsu Shoudai ◽  
Toshitaka Yamaga ◽  
Norio Akaike
Keyword(s):  
Heavy Water ◽  
Deuterium Oxide ◽  
Dependent Manner ◽  
General Anesthetics ◽  
Concentration Dependent Manner ◽  
Excitatory Postsynaptic Currents ◽  
Whole Cell ◽  
Postsynaptic Currents ◽  
Cell Current ◽  
Whole Cell Current

The effects of heavy water (deuterium oxide, D2O) on GABAergic and glutamatergic spontaneous and evoked synaptic transmission were investigated in acute brain slice and isolated “synaptic bouton” preparations of rat hippocampal CA3 neurons. The substitution of D2O for H2O reduced the frequency and amplitude of GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs) in a concentration-dependent manner but had no effect on glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs). In contrast, for evoked synaptic responses in isolated neurons, the amplitude of both inhibitory and excitatory postsynaptic currents (eIPSCs and eEPSCs) was decreased in a concentration-dependent manner. This was associated with increases of synaptic failure rate ( Rf) and paired-pulse ratio (PPR). The effect was larger for eIPSCs compared with eEPSCs. These results clearly indicate that D2O acts differently on inhibitory and excitatory neurotransmitter release machinery. Furthermore, D2O significantly suppressed GABAA receptor-mediated whole cell current ( IGABA) but did not affect glutamate receptor-mediated whole cell current ( IGlu). The combined effects of D2O at both the pre- and postsynaptic sites may explain the greater inhibition of eIPSCs compared with eEPSCs. Finally, D2O did not enhance or otherwise affect the actions of the general anesthetics nitrous oxide and propofol on spontaneous or evoked GABAergic and glutamatergic neurotransmissions, or on IGABA and IGlu. Our results suggest that previously reported effects of D2O to mimic and/or modulate anesthesia potency result from mechanisms other than modulation of GABAergic and glutamatergic neurotransmission.

scholarly journals Ionflux: A Microfluidic Approach to Ensemble Recording and Block of Whole-Cell Current from Voltage-Gated Ion Channels

2010 ◽  
Vol 98 (3) ◽  
pp. 194a ◽  
Author(s):  
C. Ian Spencer ◽  
Nianzhen Li ◽  
Juliette Johnson ◽  
Qin Chen ◽  
Cristian Ionescu-Zanetti
Keyword(s):  
Ion Channels ◽  
Whole Cell ◽  
Voltage Gated ◽  
Cell Current ◽  
Voltage Gated Ion Channels ◽  
Whole Cell Current ◽  
Gated Ion Channels

scholarly journals The Effectiveness in Activating M-Type K+ Current Produced by Solifenacin ([(3R)-1-azabicyclo[2.2.2]octan-3-yl] (1S)-1-phenyl-3,4-dihydro-1H-isoquinoline-2-carboxylate): Independent of Its Antimuscarinic Action

2021 ◽  
Vol 22 (22) ◽  
pp. 12399
Author(s):  
Hsin-Yen Cho ◽  
Tzu-Hsien Chuang ◽  
Sheng-Nan Wu
Keyword(s):  
Single Channel ◽  
Ionic Currents ◽  
Reaction Scheme ◽  
Gh3 Cells ◽  
Whole Cell ◽  
Type K ◽  
Cell Current ◽  
K Current ◽  
Subsequent Addition ◽  
Whole Cell Current

Solifenacin (Vesicare®, SOL), known to be a member of isoquinolines, is a muscarinic antagonist that has anticholinergic effect, and it has been beneficial in treating urinary incontinence and neurogenic detrusor overactivity. However, the information regarding the effects of SOL on membrane ionic currents is largely uncertain, despite its clinically wide use in patients with those disorders. In this study, the whole-cell current recordings revealed that upon membrane depolarization in pituitary GH3 cells, the exposure to SOL concentration-dependently increased the amplitude of M-type K+ current (IK(M)) with effective EC50 value of 0.34 μM. The activation time constant of IK(M) was concurrently shortened in the SOL presence, hence yielding the KD value of 0.55 μM based on minimal reaction scheme. As cells were exposed to SOL, the steady-state activation curve of IK(M) was shifted along the voltage axis to the left with no change in the gating charge of the current. Upon an isosceles-triangular ramp pulse, the hysteretic area of IK(M) was increased by adding SOL. As cells were continually exposed to SOL, further application of acetylcholine (1 μM) failed to modify SOL-stimulated IK(M); however, subsequent addition of thyrotropin releasing hormone (TRH, 1 μM) was able to counteract SOL-induced increase in IK(M) amplitude. In cell-attached single-channel current recordings, bath addition of SOL led to an increase in the activity of M-type K+ (KM) channels with no change in the single channel conductance; the mean open time of the channel became lengthened. In whole-cell current-clamp recordings, the SOL application reduced the firing of action potentials (APs) in GH3 cells; however, either subsequent addition of TRH or linopirdine was able to reverse SOL-mediated decrease in AP firing. In hippocampal mHippoE-14 neurons, the IK(M) was also stimulated by adding SOL. Altogether, findings from this study disclosed for the first time the effectiveness of SOL in interacting with KM channels and hence in stimulating IK(M) in electrically excitable cells, and this noticeable action appears to be independent of its antagonistic activity on the canonical binding to muscarinic receptors expressed in GH3 or mHippoE-14 cells.

scholarly journals [Ca2+]i oscillations in human sperm are triggered in the flagellum by membrane potential-sensitive activity of CatSper

2020 ◽  
Author(s):  
Elis Torrezan-Nitao ◽  
Sean G Brown ◽  
Esperanza Mata-Martínez ◽  
Claudia L Treviño ◽  
Christopher Barratt ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Large Scale ◽  
Conflicts Of Interest ◽  
Human Sperm ◽  
Equilibrium Potential ◽  
Current Clamp ◽  
Whole Cell ◽  
Cell Current ◽  
Whole Cell Current

Abstract STUDY QUESTION How are progesterone (P4)-induced repetitive intracellular Ca2+ concentration ([Ca2+]i) signals (oscillations) in human sperm generated? SUMMARY ANSWER P4-induced [Ca2+]i oscillations are generated in the flagellum by membrane potential (Vm)-sensitive Ca2+-influx through CatSper channels. WHAT IS KNOWN ALREADY A subset of human sperm display [Ca2+]i oscillations that regulate flagellar beating and acrosome reaction. Although pharmacological manipulations indicate involvement of stored Ca2+ in these oscillations, influx of extracellular Ca2+ is also required. STUDY DESIGN, SIZE, DURATION This was a laboratory study that used >20 sperm donors and involved more than 100 separate experiments and analysis of more than 1000 individual cells over a period of 2 years. PARTICIPANTS/MATERIALS, SETTING, METHODS Semen donors and patients were recruited in accordance with local ethics approval from Birmingham University and Tayside ethics committees. [Ca2+]i responses and Vm of individual cells were examined by fluorescence imaging and whole-cell current clamp. MAIN RESULTS AND THE ROLE OF CHANCE P4-induced [Ca2+]i oscillations originated in the flagellum, spreading to the neck and head (latency of 1–2 s). K+-ionophore valinomycin (1 µM) was used to investigate the role of membrane potential (Vm). Direct assessment by whole-cell current-clamp confirmed that Vm in valinomycin-exposed cells was determined primarily by K+ equilibrium potential (EK) and was rapidly ‘reset’ upon manipulation of [K+]o. Pre-treatment of sperm with valinomycin ([K+]o = 5.4 mM) had no effect on the P4-induced [Ca2+] transient (P = 0.95; eight experiments), but application of valinomycin to P4-pretreated sperm suppressed activity in 82% of oscillating cells (n = 257; P = 5 × 10−55 compared to control) and significantly reduced both the amplitude and frequency of persisting oscillations (P = 0.0001). Upon valinomycin washout, oscillations re-started in most cells. When valinomycin was applied in saline with elevated [K+], the inhibitory effect of valinomycin was reduced and was dependent on EK (P = 10−25). Amplitude and frequency of [Ca2+]i oscillations that persisted in the presence of valinomycin showed similar sensitivity to EK (P < 0.01). The CatSper inhibitor RU1968 (4.8 and 11 µM) caused immediate and reversible arrest of activity in 36% and 96% of oscillating cells, respectively (P < 10−10). Quinidine (300 µM) which blocks the sperm K+ current (IKsper) completely, inhibited [Ca2+]i oscillations. LARGE SCALE DATA N/A LIMITATIONS, REASONS FOR CAUTION This was an in-vitro study and caution must be taken when extrapolating these results to in-vivo regulation of sperm. WIDER IMPLICATIONS OF THE FINDINGS [Ca2+]i oscillations in human sperm are functionally important and their absence is associated with failed fertilisation at IVF. The data reported here provide new understanding of the mechanisms that underlie the regulation and generation (or failure) of these oscillations. STUDY FUNDING/COMPETING INTEREST(S) E.T.-N. was in receipt of a postgraduate scholarship from the CAPES Foundation (Ministry of Education, Brazil). E.M-M received travel funds from the Programa de Apoyo a los Estudios de Posgrado (Maestria y Doctorado en Ciencias Bioquimicas-Universidad Autonoma de Mexico). SGB and CLRB are recipients of a Chief Scientist Office (NHS Scotland) grant TCS/17/28. The authors have no conflicts of interest.

Developmental Changes in the Electrophysiological Properties and Response Characteristics of Manduca Antennal-Lobe Neurons

2002 ◽  
Vol 87 (6) ◽  
pp. 2650-2663 ◽  
Author(s):  
Alison R. Mercer ◽  
John G. Hildebrand
Keyword(s):  
Adult Development ◽  
Action Potentials ◽  
Antennal Lobe ◽  
Electrical Excitability ◽  
Whole Cell ◽  
Electrophysiological Properties ◽  
Response Characteristics ◽  
Cell Current ◽  
Whole Cell Current

Using whole cell patch-clamp recordings, we have examined changes in the electrophysiological properties and response characteristics of antennal lobe (AL) neurons associated with the metamorphic adult development of the sphinx moth, Manduca sexta. Whole cell current profiles and electrical excitability were examined in dispersed AL neurons in vitro, and in medial-group AL neurons in situ in semi-intact brain preparations. Around stages 2–4 of the 18 stages of metamorphic adult development, whole cell current profiles were dominated by large outward (K+) currents. Calcium-dependent action potentials could be elicited at this stage, but only a small percentage of cells exhibited sodium spikes. From stages 3 to 10, there was a rapid increase in the proportion of AL neurons exhibiting rapidly activating, transient sodium currents, and many cells in vitro exhibited spontaneous bursts of spike activity at this time. As development progressed, action-potential waveforms became shorter in duration and larger in amplitude. Cell-type–specific differences in the prevalence of spontaneous activity, and in the electrophysiological properties and response characteristics of AL neurons, were most apparent late in metamorphosis. While removal of antennal sensory input to the ALs early (stage 1–2) in metamorphosis had no detectable effect on the development of cell excitability, a significantly higher percentage of neurons in vitro from stage 4 pupae exhibited sodium-based action potentials following the addition of serotonin to the culture medium. Characteristic forms of electrical excitability in developing Manduca AL neurons, and their modulation by serotonin, seem likely to play a central role in the functional development of the ALs.

scholarly journals Knockdown of ASIC1 and Epithelial Sodium Channel Subunits Inhibits Glioblastoma Whole Cell Current and Cell Migration

2009 ◽  
Vol 284 (36) ◽  
pp. 24526-24541 ◽  
Author(s):  
Niren Kapoor ◽  
Rafal Bartoszewski ◽  
Yawar J. Qadri ◽  
Zsuzsanna Bebok ◽  
James K. Bubien ◽  
...  
Keyword(s):  
Cell Migration ◽  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Whole Cell ◽  
Cell Current ◽  
Whole Cell Current

Pharmacological dissection of high-voltage-activated Ca2+ current types in acutely dissociated rat supraoptic magnocellular neurons

1996 ◽  
Vol 76 (2) ◽  
pp. 977-983 ◽  
Author(s):  
R. C. Foehring ◽  
W. E. Armstrong
Keyword(s):  
High Voltage ◽  
Supraoptic Nucleus ◽  
Cell Voltage ◽  
Residual Current ◽  
Calcium Currents ◽  
Magnocellular Neurons ◽  
Whole Cell ◽  
Cell Current ◽  
P Type ◽  
Whole Cell Current

1. We used pharmacological blockers and whole cell voltage-clamp recordings from acutely dissociated magnocellular neurons from the rat supraoptic nucleus to test for the presence of L-, N-, P-, Q-, and R-type calcium currents. 2. We found clear evidence for L-type (dihydropyridine sensitive), N-type (blocked by omega-conotoxin (GVIA), and P-type (blocked by omega-agatoxin IVA) currents. Nifedipine blocked 28 +/- 2% (mean +/- SE) of the current, omega-conotoxin GVIA blocked 26 +/- 4%, and omega-agatoxin IVA (25-30 nM) blocked 17 +/- 4%. In addition, omega-conotoxin MVIIC blocked about half (54 +/- 2%) of the current remaining after L-, N-, and P-type currents were blocked, suggesting the presence of Q-type currents. 3. About 20% of the whole cell current was unblocked by the combination of all four blockers, suggesting the presence of a fifth current type. This residual current inactivated slowly at -10 mV.

Sign in / Sign up

Export Citation Format

Share Document