Contribution of changes in the chloride driving force to the fading of I GABA in frog melanotrophs

2000 ◽  
Vol 278 (3) ◽  
pp. E430-E443 ◽  
Author(s):  
Frank le Foll ◽  
Olivier Soriani ◽  
Hubert Vaudry ◽  
Lionel Cazin
Keyword(s):  
Driving Force ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Resting Potential ◽  
Perforated Patch ◽  
Induced Currents ◽  
Patch Configuration ◽  
Intracellular Chloride Concentration ◽  
Current Reversal

Chloride redistribution during type A γ-aminobutyric acid (GABAA) currents ( I GABA) has been investigated in cultured frog pituitary melanotrophs with imposed intracellular chloride concentration ([Cl−]i) in the whole cell configuration or with unaltered [Cl−]i using the gramicidin-perforated patch approach. Prolonged GABA exposures elicited reproducible decaying currents. The decay of I GABAwas associated with both a transient fall of conductance ( g GABA) and shift of current reversal potential ( E GABA). The shift of E GABAappeared to be time and driving force dependent. In the gramicidin-perforated patch configuration, repeated GABA exposures induced currents that gradually vanished. The fading of I GABA was due to persistent shifts of E GABA as a result of g GABArecovering from one GABA application to another. In cells alternatively clamped at potentials closely flanking resting potential and submitted to a train of brief GABA pulses, a reversal of I GABA was observed after 150 s recording. It is demonstrated that, in intact frog melanotrophs, shifts of E GABA combine with genuine receptor desensitization to depress I GABA. These findings strongly suggest that shifts of E GABA may act as a negative feedback, reducing the bioelectrical and secretory responses induced by an intense release of GABA in vivo.

scholarly journals Shift of Intracellular Chloride Concentration in Ganglion and Amacrine Cells of Developing Mouse Retina

2006 ◽  
Vol 95 (4) ◽  
pp. 2404-2416 ◽  
Author(s):  
Ling-Li Zhang ◽  
Hemal R. Pathak ◽  
Douglas A. Coulter ◽  
Michael A. Freed ◽  
Noga Vardi
Keyword(s):  
Gaba Receptors ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Amacrine Cells ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Mouse Retina ◽  
Intracellular Chloride ◽  
Excitatory Action ◽  
Intracellular Chloride Concentration

GABA and glycine provide excitatory action during early development: they depolarize neurons and increase intracellular calcium concentration. As neurons mature, GABA and glycine become inhibitory. This switch from excitation to inhibition is thought to result from a shift of intracellular chloride concentration ([Cl−]i) from high to low, but in retina, measurements of [Cl−]i or chloride equilibrium potential ( ECl) during development have not been made. Using the developing mouse retina, we systematically measured [Cl−]i in parallel with GABA's actions on calcium and chloride. In ganglion and amacrine cells, fura-2 imaging showed that before postnatal day (P) 6, exogenous GABA, acting via ionotropic GABA receptors, evoked calcium rise, which persisted in HCO3−- free buffer but was blocked with 0 extracellular calcium. After P6, GABA switched to inhibiting spontaneous calcium transients. Concomitant with this switch we observed the following: 6-methoxy- N-ethylquinolinium iodide (MEQ) chloride imaging showed that GABA caused an efflux of chloride before P6 and an influx afterward; gramicidin-perforated-patch recordings showed that the reversal potential for GABA decreased from −45 mV, near threshold for voltage-activated calcium channel, to −60 mV, near resting potential; MEQ imaging showed that [Cl−]i shifted steeply around P6 from 29 to 14 mM, corresponding to a decline of ECl from −39 to −58 mV. We also show that GABAergic amacrine cells became stratified by P4, potentially allowing GABA's excitatory action to shape circuit connectivity. Our results support the hypothesis that a shift from high [Cl−]i to low causes GABA to switch from excitatory to inhibitory.

Mechanisms of neocortical epileptogenesis in vitro

1982 ◽  
Vol 48 (6) ◽  
pp. 1321-1335 ◽  
Author(s):  
M. J. Gutnick ◽  
B. W. Connors ◽  
D. A. Prince
Keyword(s):  
Reversal Potential ◽  
Excitatory Input ◽  
Short Latency ◽  
Resting Potential ◽  
Excitatory Postsynaptic Potential ◽  
Cellular Mechanisms ◽  
Voltage Dependent ◽  
Intact Cortex

1. The cellular mechanisms underlying interictal epileptogenesis have been examined in an in vitro slice preparation of guinea pig neocortex. Penicillin or bicuculline was applied to the tissue, and intracellular recordings were obtained from neurons and glia. 2. Following convulsant application, stimulation could elicit a short-latency excitatory postsynaptic potential (EPSP) and a large, longer latency depolarization shift (DS) in single neurons. DSs in neurons of the slice were very similar to those evoked in neurons of neocortex in vivo in that they displayed an all-or-none character, large shifts in latency during repetitive stimuli, long afterpotentials, and a prolonged refractory period. In contrast to epileptogenesis produced by penicillin in intact cortex, neither spontaneous DSs nor ictal episodes were observed in neocortical slices. 3. In simultaneous recordings from pairs of neurons within the same cortical column, DS generation and latency shifts were invariably synchronous. DS generation in neurons was also coincident with large, paroxysmal increases of extracellular [K+], as indicated by simultaneous recordings from glia. 4. When polarizing currents were applied to neurons injected with the local anesthetic QX-314, the DS amplitude varied monotonically and had an extrapolated reversal potential near 0 mV. In neurons injected with the K+-current blocker Cs+, large displacements of membrane potential were possible, and both the short-latency EPSP and the peak of the DS diminished completely at about 0 mV. At potentials positive to this, the short-latency EPSP was reversed, and the DS was replaced by a paroxysmal hyperpolarization whose rise time and peak latency were prolonged compared to the DS evoked at resting potential. The paroxysmal hyperpolarization probably represents the prolonged activation of the impaled neuron by EPSPs. 5. Voltage-dependent components, including slow spikes, appeared to contribute to generation of the DS at resting potential in Cs+-filled cells, and these components were blocked during large depolarizations. 6. The results suggest that DS generation in single neocortical neurons occurs during synchronous synaptic activation of a large group of cells. DS onset in a given neuron is determined by the timing of a variable-latency excitatory input that differs from the short-latency EPSP. The DS slow envelope appears to be generated by long-duration excitatory synaptic currents and may be modulated by intrinsic voltage-dependent membrane conductances. 7. We present a hypothesis for the initiation of the DS, based on the anatomical and physiological organization of the intrinsic neocortical circuits.

Possible Effects of Depolarizing GABAA Conductance on the Neuronal Input–Output Relationship: A Modeling Study

2005 ◽  
Vol 93 (6) ◽  
pp. 3504-3523 ◽  
Author(s):  
Kenji Morita ◽  
Kunichika Tsumoto ◽  
Kazuyuki Aihara
Keyword(s):  
Firing Rate ◽  
Cortical Neurons ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Resting Potential ◽  
Input Output ◽  
Wide Range ◽  
The Relationship

Recent in vitro experiments revealed that the GABAA reversal potential is about 10 mV higher than the resting potential in mature mammalian neocortical pyramidal cells; thus GABAergic inputs could have facilitatory, rather than inhibitory, effects on action potential generation under certain conditions. However, how the relationship between excitatory input conductances and the output firing rate is modulated by such depolarizing GABAergic inputs under in vivo circumstances has not yet been understood. We examine herewith the input–output relationship in a simple conductance-based model of cortical neurons with the depolarized GABAA reversal potential, and show that a tonic depolarizing GABAergic conductance up to a certain amount does not change the relationship between a tonic glutamatergic driving conductance and the output firing rate, whereas a higher GABAergic conductance prevents spike generation. When the tonic glutamatergic and GABAergic conductances are replaced by in vivo–like highly fluctuating inputs, on the other hand, the effect of depolarizing GABAergic inputs on the input–output relationship critically depends on the degree of coincidence between glutamatergic input events and GABAergic ones. Although a wide range of depolarizing GABAergic inputs hardly changes the firing rate of a neuron driven by noncoincident glutamatergic inputs, a certain range of these inputs considerably decreases the firing rate if a large number of driving glutamatergic inputs are coincident with them. These results raise the possibility that the depolarized GABAA reversal potential is not a paradoxical mystery, but is instead a sophisticated device for discriminative firing rate modulation.

GABAA-Dependent Chloride Influx Modulates Reversal Potential of GABAB-Mediated IPSPs in Hippocampal Pyramidal Cells

2001 ◽  
Vol 85 (6) ◽  
pp. 2381-2387
Author(s):  
Valeri Lopantsev ◽  
Philip A. Schwartzkroin
Keyword(s):  
Membrane Potential ◽  
Mossy Fiber ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Intracellular Chloride ◽  
The Impact ◽  
Intracellular Chloride Concentration ◽  
Chloride Influx ◽  
Hippocampal Pyramidal Cells

Changes in intracellular chloride concentration, mediated by chloride influx through GABAA receptor–gated channels, may modulate GABAB receptor–mediated inhibitory postsynaptic potentials (GABAB IPSPs) via unknown mechanisms. Recording from CA3 pyramidal cells in hippocampal slices, we investigated the impact of chloride influx during GABAA receptor–mediated IPSPs (GABAA IPSPs) on the properties of GABAB IPSPs. At relatively positive membrane potentials (near −55 mV), mossy fiber–evoked GABAB IPSPs were reduced (compared with their magnitude at −60 mV) when preceded by GABAAreceptor–mediated chloride influx. This effect was not associated with a correlated reduction in membrane permeability during the GABAB IPSP. The mossy fiber–evoked GABAB IPSP showed a positive shift in reversal potential (from −99 to −93 mV) when it was preceded by a GABAA IPSP evoked at cell membrane potential of −55 mV as compared with −60 mV. Similarly, when intracellular chloride concentration was raised via chloride diffusion from an intracellular microelectrode, there was a reduction of the pharmacologically isolated monosynaptic GABABIPSP and a concurrent shift of GABAB IPSP reversal potential from −98 to −90 mV. We conclude that in hippocampal pyramidal cells, in which “resting” membrane potential is near action potential threshold, chloride influx via GABAA IPSPs shifts the reversal potential of subsequent GABAB receptor–mediated postsynaptic responses in a positive direction and reduces their magnitude.

Method for manipulation of cytosolic pH in cells clamped in the whole cell or perforated-patch configurations

1994 ◽  
Vol 267 (4) ◽  
pp. C1152-C1159 ◽  
Author(s):  
S. Grinstein ◽  
R. Romanek ◽  
O. D. Rotstein
Keyword(s):  
Single Cells ◽  
Reversal Potential ◽  
Patch Clamp Technique ◽  
Intact Cells ◽  
Pipette Solution ◽  
Whole Cell ◽  
Perforated Patch ◽  
Cell Configuration ◽  
Patch Configuration ◽  
In Cells

A number of methods have been developed to manipulate the intracellular pH (pHi) of intact cells. However, such methods are not applicable when cells are studied using the patch-clamp technique, due to the continuity of the cell interior with the recording pipette. The perfused-pipette method can be used to modify pHi in the whole cell configuration, but this approach is slow, technically demanding, and not useful in the case of the perforated-patch configuration. In this report, we introduce a simple procedure that enables the investigator to predictably and reversibly alter pHi in cells clamped in either the whole cell or perforated-patch modes. The method is based on the provision of a virtually unlimited reservoir of an intracellular H+ (equivalent) donor/acceptor system, by inclusion of large concentrations of permeable weak electrolytes in the pipette solution. This system not only provides a means for the imposition and maintenance of a chosen pHi but, by changing the external concentration of the weak electrolyte, enables the investigator to rapidly and reversibly change pHi or the transmembrane delta pH during the course of an experiment. The effectiveness of the procedure was validated in peritoneal macrophages by two methods: 1) direct measurement of pHi in single cells by fluorescence ratio determinations and 2) estimation of the reversal potential of H(+)-selective currents. The pHi clamping procedure is shown to be effective using either organic or inorganic weak bases in the whole cell configuration. In addition, because NH+4/NH3 can readily permeate the pores formed by nystatin or amphotericin, the method is also shown to apply to the perforated-patch configuration.

scholarly journals Current Separations in Myxicola Giant Axons

1969 ◽  
Vol 54 (6) ◽  
pp. 741-754 ◽  
Author(s):  
L. Goldman ◽  
L. Binstock
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Reversal Potential ◽  
Transient Current ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Resting Membrane Potential ◽  
Concentration Data ◽  
Giant Axons ◽  
Current Reversal

The effect of reducing the external sodium concentration, [Na]o, on resting potential, action potential, membrane current, and transient current reversal potential in Myxicola giant axons was studied. Tris chloride was used as a substitute for NaCl. Preliminary experiments were carried out to insure that the effect of Tris substitution could be attributed entirely to the reduction in [Na]o. Both choline and tetramethylammonium chloride were found to have additional effects on the membrane. The transient current is carried largely by Na, while the delayed current seems to be independent of [Na]o. Transient current reversal potential behaves much like a pure Nernst equilibrium potential for sodium. Small deviations from this behavior are consistent with the possibility of some small nonsodium component in the transient current. An exact PNa/PK for the transient current channels could not be computed from these data, but is certainly well greater than unity and possibly quite large. The peak of the action potential varied with [Na]o as expected for a sodium action potential with some substantial potassium permeability at the time of peak. Resting membrane potential is independent of [Na]o. This finding is inconsistent with the view that the resting membrane potential is determined only by the distribution of K and Na, and PNa/PK. It is suggested that PNa/PK's obtained from resting membrane potential-potassium concentration data do not always have the physical meaning generally attributed to them.

A Critical Study of the Evidence for Peripheral Inhibitory Axons in Insects

1968 ◽  
Vol 49 (1) ◽  
pp. 201-222
Author(s):  
P. N. R. USHERWOOD
Keyword(s):  
Potassium Concentration ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Critical Study ◽  
Muscle Fibres ◽  
High Concentration ◽  
Bathing Medium

1. The metathoracic anterior coxal adductor (a.c.a.) muscle of the locust and the grasshopper is innervated by a peripheral inhibitory axon similar to the inhibitory axon which innervates the metathoracic extensor tibiae muscles of these insects. No evidence was found to justify calling this axon an inhibitory-conditioning axon. 2. Hyperpolarizing inhibitory postsynaptic potentials (IPSPs) are normally recorded from a.c.a. muscle fibres during stimulation of this axon, and if the bathing medium contains a high concentration of potassium ions the tonic fibres of the a.c.a. muscle relax slightly during inhibitory stimulation. 3. The IPSPs are chloride potentials and can be converted to depolarizing responses by changing either the external or internal chloride concentration of the a.c.a. muscle fibres. Depolarizing IPSPs are frequently accompanied by small contractions of a.c.a. muscle fibres innervated by the inhibitory axon. 4. The a.c.a. muscle fibres are permeable to potassium and chloride ions but influx of potassium chloride is much faster than efflux. Therefore when a.c.a. muscle fibres are loaded with chloride by exposing them to high-K saline (20-100 m-equiv. potassium/l.) and are then returned to normal (10 m-equiv. potassium/l.) saline the internal chloride concentration remains elevated for some time and during this period the equilibrium potential for the inhibitory response is less negative than the resting potential and the IPSPs are depolarizing. 5. Depolarizing IPSPs are usually recorded from a.c.a. muscle fibres of locusts and grasshoppers when these fibres are transferred from their normal bathing medium, haemolymph, to 10 K saline. Probably the main reason for this reversal of the IPSPs is the entry of KCl into the muscle fibres during dissection of the nerve-muscle preparations. Large quantities of KCl would be released into the environment surrounding these preparations from muscle fibres cut and removed during dissection. 6.Depolarizing IPSPs were more frequently recorded from muscle fibres of grassfed locusts than from fibres of starved locusts. The potassium concentration of haemolymph of grass fed locusts is higher than that of locust saline (10 m-equiv./l.). 7. The potassium concentration of locust haemolymph presumably fluctuates in vivo but these fluctuations are too slow to affect the sign of the IPSP. The IPSPs are therefore always hyperpolarizing in vivo. 8. The effect of changes in the potassium concentration of the bathing medium on the magnitude and polarity of the IPSP could account for the diverse responses recorded previously from a.c.a. muscle fibres of locusts and grasshoppers.

scholarly journals KCC2-dependent Steady-state Intracellular Chloride Concentration and pH in Cortical Layer 2/3 Neurons of Anesthetized and Awake Mice

2017 ◽  
Author(s):  
Juan Carlos Boffi ◽  
Johannes Knabbe ◽  
Michaela Kaiser ◽  
Thomas Kuner
Keyword(s):  
Steady State ◽  
Cortical Neurons ◽  
Chloride Concentration ◽  
Cortical Layer ◽  
Model Systems ◽  
Adult Mice ◽  
Neuronal Inhibition ◽  
Wide Range ◽  
Intracellular Chloride Concentration

AbstractNeuronal intracellular Cl- concentration ([Cl-]i) influences a wide range of processes such as neuronal inhibition, membrane potential dynamics, intracellular pH (pHi) or cell volume. Up to date, neuronal [Cl-]i has predominantly been studied in model systems of reduced complexity. Here, we implemented the genetically encoded ratiometric Cl- indicator Superclomeleon (SCLM) to estimate the steady-state [Cl-]i in cortical neurons from anesthetized and awake mice using 2-photon microscopy. Additionally, we implemented superecliptic pHluorin as a ratiometric sensor to estimate the intracellular steady-state pH (pHi) of mouse cortical neurons in vivo. We estimated an average resting [Cl-]i of 6 ± 2 mM with no evidence of subcellular gradients in the proximal somato-dendritic domain and an average somatic pHi of 7.1 ± 0.1. Neither [Cl-]i nor pHi were affected by isoflurane anesthesia. We deleted the cation-Cl- co-transporter KCC2 in single identified neurons of adult mice and found an increase of [Cl-]i to approximately 26 ± 8 mM, demonstrating that under in vivo conditions KCC2 produces low [Cl-]i in adult mouse neurons. In summary, neurons of the brain of awake adult mice exhibit a low and evenly distributed [Cl-]i in the proximal somato-dendritic compartment that is independent of anesthesia and requires KCC2 expression for its maintenance.

scholarly journals Simultaneous two-photon imaging of intracellular chloride concentration and pH in mouse pyramidal neurons in vivo

2017 ◽  
Vol 114 (41) ◽  
pp. E8770-E8779 ◽  
Author(s):  
Sebastian Sulis Sato ◽  
Pietro Artoni ◽  
Silvia Landi ◽  
Olga Cozzolino ◽  
Riccardo Parra ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Chloride Concentration ◽  
Intracellular Chloride ◽  
Two Photon ◽  
Photon Imaging ◽  
Two Photon Imaging ◽  
Intracellular Chloride Concentration
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