Differentiation-dependent changes in the membrane properties of fiber cells isolated from the rat lens

2008 ◽  
Vol 294 (5) ◽  
pp. C1133-C1145 ◽  
Author(s):  
Kevin F. Webb ◽  
Paul J. Donaldson
Keyword(s):  
Large Population ◽  
Reversal Potential ◽  
Membrane Resistance ◽  
Cellular Level ◽  
Membrane Properties ◽  
Nonselective Cation Channel ◽  
Impedance Measurements ◽  
Fiber Cells ◽  
Anion Conductance ◽  
Ion Substitution

Impedance measurements in whole lenses showed that lens fiber cells possess different permeability properties to the epithelial cells from which they differentiate. To confirm these observations at the cellular level, we analyzed the membrane properties of fiber cells isolated in the presence of the nonselective cation channel inhibitor Gd3+. Isolated fiber cells were viable in physiological [Ca2+] and exhibited a range of lengths that reflected their stage of differentiation. Analysis of a large population of fiber cells revealed a subgroup of cells whose conductivity matched values measured in the whole lens ( 1 ). In this group of cells, membrane resistance, conductivity, and reversal potential all varied with cell length, suggesting that the process of differentiation is associated with a change in the membrane properties of fiber cells. Using pharmacology and ion substitution experiments, we showed that newly differentiated fiber cells (<150 μm) contained variable combinations of Ba2+-and tetraethylammonium-sensitive K+ currents. Longer fiber cells (150–650 μm) were dominated by a lyotropic anion conductance, which also appears to plays a role in the intact lens. Longer cells also exhibited a low-level, nonselective conductance that was eliminated by the replacement of extracellular Na+ with N-methyl-d-glucamine, indicating that the lens contains both Gd3+-sensitive and -insensitive nonselective cation conductances. Fiber cell differentiation is therefore associated with a shift in membrane permeability from a dominant K+ conductance(s) toward larger contributions from anion and nonselective cation conductances as fiber cells elongate.

scholarly journals Ionic mechanisms of two types of on-center bipolar cells in the carp retina. I. The responses to central illumination.

1979 ◽  
Vol 73 (1) ◽  
pp. 73-90 ◽  
Author(s):  
T Saito ◽  
H Kondo ◽  
J I Toyoda
Keyword(s):  
Reversal Potential ◽  
Maximum Amplitude ◽  
Bipolar Cells ◽  
Light Spot ◽  
Membrane Properties ◽  
Resistance Increase ◽  
Membrane Conductances ◽  
Electric Interaction ◽  
Ionic Mechanisms ◽  
Resistance Decrease

Properties of the depolarizing response of on-center bipolar cells to a light spot stimulus were studied in the carp retina. On-center bipolar cells were classified into two types, cone-dominant and rod-dominant, according to their major input from cones and rods. Cone-dominant bipolar cells responded to spectral light with the maximum amplitude near 625 nm, suggesting major input from red cones. The response was accompanied by a resistance increase and showed a reversal potential at -63 +/- 21 mV when the membrane was hyperpolarized by current. The results suggest that the photoresponse of cone-dominant cells is due to a decrease of gK and/or gCl, membrane conductances to potassium and chloride, respectively. Rod-dominant bipolar cells responded to spectral light with the maximum amplitude near 525 nm under scotopic conditions and near 625 nm under photopic conditions, providing evidence that they receive input from rods and red cones. In the scoptopic condition their response was accompanied by a resistance decrease and showed a reversal potential at 29 +/- 13 mV, whereas in the photopic condition the response in most of them was accompanied by a resistance increase, at least in their part and showed a reversal at -53 +/- 11 mV. The results suggest that the photoresponse activated by rod input is due to an increase in gNa. In the mesopic condition rod-dominant cells showed complex electrical membrane properties as the result of electric interaction between the above two differnt ionic mechanisms activated by rod and cone inputs.

Effects of norepinephrine upon superficial layer neurons in the superior colliculus of the hamster: In vitro studies

1999 ◽  
Vol 16 (3) ◽  
pp. 557-570 ◽  
Author(s):  
HONGJING TAN ◽  
RICHARD D. MOONEY ◽  
ROBERT W. RHOADES
Keyword(s):  
Superior Colliculus ◽  
Optic Tract ◽  
Reversal Potential ◽  
Outward Current ◽  
Input Resistance ◽  
Superficial Layer ◽  
Membrane Properties ◽  
Induced Response

Intracellular recording techniques were used to evaluate the effects of norepinephrine (NE) on the membrane properties of superficial layer (stratum griseum superficiale and stratum opticum) superior colliculus (SC) cells. Of the 207 cells tested, 44.4% (N = 92) were hyperpolarized by ≥3 mV and 8.7% (N = 18) were depolarized by ≥3 mV by application of NE. Hyperpolarization induced by NE was dose dependent (EC50 = 8.1 μM) and was associated with decreased input resistance and outward current which had a reversal potential of −94.0 mV. Depolarization was associated with a very slight rise in input resistance and had a reversal potential of −93.1 mV for the single cell tested. Pharmacologic experiments demonstrated that isoproterenol, dobutamine, and p-aminoclonidine all hyperpolarized SC cells. These results are consistent with the conclusion that NE-induced hyperpolarization of SC cells is mediated by both α2 and β1 adrenoceptors. The α1 adrenoceptor agonists, methoxamine and phenylephrine, depolarized 35% (6 of 17) of the SC cells tested by ≥3 mV. Most of the SC cells tested exhibited responses indicative of expression of more than one adrenoceptor. Application of p-aminoclonidine or dobutamine inhibited transsynaptic responses in SC cells evoked by electrical stimulation of optic tract axons. Inhibition of evoked responses by these agents was usually, but not invariably, associated with a hyperpolarization of the cell membrane and a reduction in depolarizing potentials evoked by application of glutamate. The present in vitro results are consistent with those of the companion in vivo study which suggested that NE-induced response suppression in superficial layer SC neurons was primarily postsynaptic and chiefly mediated by both α2 and β1 adrenoceptors.

scholarly journals Responses of the Smooth Muscle Membrane of Guinea Pig Jejunum Elicited by Field Stimulation

1969 ◽  
Vol 53 (4) ◽  
pp. 471-486 ◽  
Author(s):  
T. Hidaka ◽  
H. Kuriyama
Keyword(s):  
Reversal Potential ◽  
Membrane Resistance ◽  
Muscle Membrane ◽  
Field Stimulation ◽  
Applied Current ◽  
Smooth Muscle Membrane ◽  
Inhibitory Potential ◽  
Low K ◽  
Excitatory Potential ◽  
Pig Jejunum

Field stimulation of the jejunum elicited successively an action potential of spike form, a slow excitatory depolarization, a slow inhibitory hyperpolarization, and a postinhibitory depolarization as a rebound excitation. The slow depolarization often triggered the spike. The inhibitory potential showed lower threshold than did the excitatory potential. Both the excitatory potentials were abolished by atropine and tetrodotoxin. Effective membrane resistance measured by the intracellular polarizing method was reduced during the peak of the excitatory potential, but the degree of reduction was smaller than that evoked by iontophoretic application of acetylcholine. Conditioning hyperpolarization of the muscle membrane modified the amplitude of the excitatory potential. The estimated reversal potential level for the excitatory potenialt was about 0 mv. No changes could be observed in the amplitude of the inhibitory potential when hyperpolarization was induced with intracellularly applied current. Low [K]o and [Ca]o blocked the generation of the excitatory potential but the amplitude of the inhibitory potential was enhanced in low [K]o. Low [Ca]o and high [Mg]o had no effect on the inhibitory potential.

The Mechanical Properties of the Longitudinal Muscle in the Earthworm

1969 ◽  
Vol 50 (2) ◽  
pp. 431-443 ◽  
Author(s):  
T. HIDAKA ◽  
H. KURIYAMA ◽  
T. YAMAMOTO
Keyword(s):  
Mechanical Properties ◽  
Longitudinal Muscle ◽  
Sodium Concentration ◽  
Membrane Resistance ◽  
Membrane Properties ◽  
Active Tension ◽  
Spike Generation ◽  
Tension Development ◽  
Sustained Contraction ◽  
Intracellular Stimulation

1. A study of the mechanical properties of longitudinal muscle in relation to the membrane properties was carried out under isometric conditions. 2. When the stimulus duration exceeded 50 msec., active tension development was followed by sustained contraction. The sustained contractions were not related to spike generation. 3. The critical potassium concentration to produce the contracture depolarized the membrane from -36 to -20 mV. 4. Reduced sodium concentration and increased calcium and increased potassium (up to 27 mM) concentrations enhanced the amplitude of the active tension. 5. Reduced sodium concentration enhanced the amplitude and duration of the sustained tension, but increased potassium and calcium concentrations reduced them. 6. Caffeine (12 mM) induced contractures of the muscle, and reduced the membrane resistance and capacitance. 7. Spikes were not elicited by intracellular stimulation. 8. 5-Hydroxytryptamine (10-5 g./ml.) blocked the generation of the sustained contraction but no effect was observed on the phasic tension.

Synaptic and intrinsic control of membrane excitability of neostriatal neurons. II. An in vitro analysis

1990 ◽  
Vol 63 (4) ◽  
pp. 663-675 ◽  
Author(s):  
P. Calabresi ◽  
N. B. Mercuri ◽  
G. Bernardi
Keyword(s):  
Membrane Potential ◽  
Tetanus Toxin ◽  
Reversal Potential ◽  
Membrane Potentials ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Epsp Amplitude ◽  
The Relationship

1. The effects of intrinsic membrane properties on the spontaneous and synaptically evoked activity of neostriatal neurons were studied in an in vitro slice preparation with the use of intracellular recordings. The recorded neurons did not show spontaneous action potentials at rest; depolarizing current pulses triggered a tonic firing pattern. 2. Subthreshold spontaneous depolarizing potentials (SDPs) were observed in 52% of the recorded neurons. The amplitude of these potentials at rest ranged between 2 and 15 mV, and their duration between 4 and 100 ms. The frequency and the amplitude of the SDPs were functions of the membrane potential: membrane depolarization by constant positive current increased the frequency of the SDPs and reduced their amplitude; hyperpolarization of the membrane decreased their frequency and increased their amplitude. Often, at membrane potentials more negative than -90 mV, SDPs were completely suppressed. 3. SDPs were blocked by low calcium-cobalt containing solutions. In the presence of tetrodotoxin (TTX, 1-3 microM), SDPs were completely abolished in 50% of the tested neurons; in the remaining neurons, small (1-4 mV) TTX-resistant SDPs were observed. In most of the neurons, bicuculline (BIC, 10-100 microM) and low concentrations of tetanus toxin (5-10 micrograms/ml) did not clearly affect the SDPs. Higher concentrations of tetanus toxin (100 micrograms/ml) blocked the SDPs as well as the synaptic potentials evoked by intrastriatal stimulation. 4. At resting membrane potential, intrastriatal stimulation produced a fast depolarizing postsynaptic potential (EPSP) that was reduced by BIC (10-100 microM). The relationship between EPSP amplitude and membrane potential was studied either by utilizing K(+)-chloride electrodes or by the use of cesium-chloride electrodes. In both these cases, the reversal potential for the EPSPs was between 0 and -14 mV. In cesium-loaded neurons, the decrease of the EPSP, usually observed at negative membrane potentials (below -85 mV), was clearly reduced. Internal cesium prolonged the duration of the SDPs and the EPSPs evoked by intrastriatal stimulation. 5. The relationship between spontaneous and evoked synaptic activity and membrane potential was studied in the presence of different external potassium blockers. 4-Aminopyridine (4AP, 0.1-1 mM) increased the EPSP amplitude and the frequency of the SDPs, but did not decrease membrane rectification and the shunt of the EPSPs present at negative membrane potentials. On the contrary, rectification of the membrane and the shunt of the EPSPs below -85 mV were clearly reduced by tetraethylammonium (TEA, 10-20 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

Bullfrog dorsal root ganglion cells having tetrodotoxin-resistant spikes are endowed with nicotinic receptors

1989 ◽  
Vol 62 (3) ◽  
pp. 657-664 ◽  
Author(s):  
K. Morita ◽  
Y. Katayama
Keyword(s):  
Dorsal Root Ganglion ◽  
Conduction Velocity ◽  
Dorsal Root ◽  
Time Course ◽  
Ganglion Cells ◽  
Reversal Potential ◽  
Membrane Resistance ◽  
Fast Response ◽  
Dorsal Root Ganglion Cells

1. Intracellular recordings were made from bullfrog dorsal root ganglion (DRG) neurons in vitro. They were divided into three types, As, Ar, and C, according to their conduction velocity and their sensitivity to tetrodotoxin [TTX (less than or equal to 1 microM)]; an As neuron had a fast conduction velocity (13-50 m/s, mean = 31 m/s, n = 73) and TTX-sensitive sodium soma spikes: an Ar neuron showed a fast conduction velocity (4-28 m/s, mean = 14 m/s, n = 52) and TTX-resistant sodium soma spikes; and a C neuron had a slow conduction velocity (0.16-0.8 m/s, mean = 0.4 m/s, n = 49) and TTX-resistant sodium-calcium soma spikes. 2. Superfusion of acetylcholine [ACh (0.3 microM-1 mM)] produced a fast depolarization in 70% of Ar and in 50% of C neurons. No As neuron showed a fast depolarization in response to ACh. The ACh-induced fast response persisted in calcium-free or TTX-containing solutions. 3. The response in both Ar and C neurons was similar except in time course; the response was always more rapid in C than in Ar neurons. The response was always associated with a decreased membrane resistance and reversed in polarity at about -30 mV. The reversal potential varied with both sodium and potassium concentrations of the superfusing solutions. 4. Nicotine, (+)-tubocurarine [(+)-TC], and hexamethonium reversibly blocked the ACh fast response.(ABSTRACT TRUNCATED AT 250 WORDS)

Dendritic arbor of locus coeruleus neurons contributes to opioid inhibition

1996 ◽  
Vol 75 (5) ◽  
pp. 2029-2035 ◽  
Author(s):  
R. A. Travagli ◽  
M. Wessendorf ◽  
J. T. Williams
Keyword(s):  
Locus Coeruleus ◽  
Horizontal Plane ◽  
Reversal Potential ◽  
Outward Current ◽  
Membrane Properties ◽  
Equilibrium Potential ◽  
Intrinsic Membrane Properties ◽  
In Cells

1. The nucleus locus coeruleus (LC) is made up of noradrenergic cells all of which are hyperpolarized by opioids. Recent work has shown that the reversal potential of the opioid-induced current is more negative than the potassium equilibrium potential. The aim of the present study was to determine whether the extent of the dendritic field could contribute to the very negative opioid reversal potential. 2. Individual LC cells were labeled in the brain slice preparation. The number of dendrites found on cells in slices sectioned in the horizontal plane was greater than cells in coronal slices. However, the dimensions of the cell body slices from each plane were not significantly different. 3. The resting conductance of neurons from slices cut in the horizontal plane was significantly larger than in cells from coronal plane. 4. The amplitude of the outward current induced by [Met5]-enkephalin (ME) was larger in cells from horizontal slices and the reversal potential was more negative than that of cells in coronal slices. 5. The results show that the plane of section influences the membrane properties and opioid actions of LC neurons in vitro and suggest that these differences correlate with the numbers of dendrites. The results suggest that in vivo, in addition to intrinsic membrane properties and synaptic inputs, the structural makeup of the nucleus is an important factor in determining the activity.

K+-channel blockers do not decrease acetylcholine depolarizations in canine trachealis

1992 ◽  
Vol 70 (1) ◽  
pp. 43-52 ◽  
Author(s):  
E. E. Daniel ◽  
J. Jury ◽  
R. Serio ◽  
L. P. Jager
Keyword(s):  
Chloride Channels ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Resting Potential ◽  
K Channel ◽  
Channel Blockers ◽  
Membrane Effects ◽  
Sucrose Gap ◽  
Time Courses

Using the double sucrose gap, we have examined the role of K+ channels in the cholinergic depolarizations in response to field stimulation and acetylcholine (Ach) in canine trachealis. Acetylcholine-like depolarization per se decreased electrotonic potentials from hyperpolarizing currents. The net effect of acetylcholine (10−6 M) depolarization on membrane conductance was a small increase after the depolarization was compensated by current clamp. Reversal potentials for acetylcholine depolarization and for the excitatory junction potential (EJP) were determined by extrapolation to be 20–30 mV positive to the resting potential, previously shown to be approximately −55 mV. They were shifted positively by tetraethylammonium ion (TEA) at 20 mM or Ba2+ at 1 mM. TEA or Ba2+ initially depolarized the membrane and increased membrane resistance. Repolarization of the membrane restored any reductions in EJP amplitudes associated with depolarization. After 15 min, the membrane potential partially repolarized, and acetylcholine-induced depolarization and contractions were then increased by TEA. 4-Aminopyridine depolarized the membrane but decreased membrane resistance. Apamin (10−6 M), charybdotoxin (10−7 M), and glybenclamide (10−5 M) each failed to significantly depolarize membranes, increase membrane resistance, or reduce EJP amplitudes or depolarization to 10−6 M Ach. Glybenclamide reduced depolarizations to added acetylcholine slightly. TEA occasionally reduced the EJP markedly, but this was shown to be most likely a prejunctional effect mediated by norepinephrine release. TEA alone among K+-channel blockers slowed the onset and the time courses of the EJP as well as the acetylcholine-induced depolarization. K+-channel closure cannot be a complete explanation of acetylcholine-induced membrane effects on this tissue. Acetylcholine must have increased the conductance of an ion with a reversal potential positive to the resting potential in addition to any effect to close K+ channels.Key words: acetylcholine, tracheal smooth muscle, trachea, chloride channels, sucrose gap, potassium channels, tetraethylammonium, Ba2+.

Physiological response properties of displaced amacrine cells of the adult ferret retina

2004 ◽  
Vol 21 (2) ◽  
pp. 135-144 ◽  
Author(s):  
SALLY W. ABOELELA ◽  
DAVID W. ROBINSON
Keyword(s):  
Large Population ◽  
Amacrine Cells ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Oscillatory Activity ◽  
Large Field ◽  
Resting Membrane Potential ◽  
Mammalian Retina ◽  
Displaced Amacrine Cells ◽  
Intrinsic Membrane Properties

The ganglion cell layer (GCL) of the mammalian retina contains a large number of neurons called displaced amacrine cells (DACs) that do not project to the optic nerve. However, with the exception of the rabbit starburst amacrine cell little is known regarding the function of this large population due to the difficulty experienced in making physiological recordings from these neurons. We have overcome these difficulties and have used whole-cell patch-clamp techniques to examine the intrinsic membrane properties of DACs in the ferret retina. Our results indicate a large degree of diversity in their intrinsic membrane properties. In response to maintained depolarizing current injection, DACs responded with graded depolarization or by eliciting either transient or sustained bursts of spiking activity. At the resting membrane potential, 10% of the DACs generated spontaneous spikes in either an apparently random manner or at the peak of intrinsic waves of depolarization. The resting membrane activity of the remaining DACs recorded could be classified into three groups that were quiescent (28%), had robust uncorrelated synaptic activity (30%), or underwent slow waves of depolarization (42%). Diversity was also revealed in the membrane currents recorded in voltage-clamp where some DACs were quiescent (19%), or exhibited robust nonrhythmic synaptic events (42%). The remaining DACs exhibited waves of oscillatory activity (39%), characterized by either rhythmic bursts of synaptic events (17%) or slow inward currents (22%). Bath application of 50 μM biccuculine or 150 μM picrotoxin had no effect on the waves of activity, however, the gap junction blocker, carbenoxolone (100 μm), blocked both oscillatory patterns. By including Lucifer yellow and biocytin in the recording pipette, it was possible to determine the morphology of recorded neurons and group them based on dendritic extent as small-, medium-, or large-field DACs. There were few relationships between these morphologically defined groups and their intrinsic membrane properties. The present study provides the first in-depth examination of the intrinsic membrane properties of DACs in the ferret retina and provides new insights into the potential roles these neurons play in the processing of visual information in the mammalian retina.

Synchronization properties of spindle oscillations in a thalamic reticular nucleus model

1994 ◽  
Vol 72 (3) ◽  
pp. 1109-1126 ◽  
Author(s):  
D. Golomb ◽  
X. J. Wang ◽  
J. Rinzel
Keyword(s):  
Time Course ◽  
Cluster State ◽  
Large Population ◽  
Reversal Potential ◽  
Ionic Currents ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Quiescent State ◽  
Gamma Aminobutyric Acid ◽  
Cluster States

1. We address the hypothesis of Steriade and colleagues that the thalamic reticular nucleus (RE) is a pacemaker for thalamocortical spindle oscillations by developing and analyzing a model of a large population of all-to-all coupled inhibitory RE neurons. 2. Each RE neuron has three ionic currents: a low-threshold T-type Ca2+ current (ICa-T), a calcium-activated potassium current (IAHP) and a leakage current (IL). ICa-T underlies a cell's postinhibitory rebound properties, whereas IAHP hyperpolarizes the neuron after a burst. Each neuron, which is a conditional oscillator, is coupled to all other RE neurons via fast gamma-aminobutyric acid-A (GABAA) and slow GABAB synapses. 3. For generating network oscillations IAHP may not be necessary. Synaptic inhibition can provide the hyperpolarization for deinactivating ICa-T that causes bursting if the reversal potentials for GABAA and GABAB synapses are sufficiently negative. 4. If model neurons display sufficiently powerful rebound excitability, an isolated RE network of such neurons oscillates with partial but typically not full synchrony. The neurons spontaneously segregate themselves into several macroscopic clusters. The neurons within a cluster follow the same time course, but the clusters oscillate differently from one another. In addition to activity patterns in which clusters burst sequentially (e.g., 2 or 3 clusters bursting alternately), a two-cluster state may occur with one cluster active and one quiescent. Because the neurons are all-to-all coupled, the cluster states do not have any spatial structure. 5. We have explored the sensitivity of such partially synchronized patterns to heterogeneity in cells' intrinsic properties and to simulated neuroelectric noise. Although either precludes precise clustering, modest levels of heterogeneity or noise lead to approximate clustering of active cells. The population-averaged voltage may oscillate almost regularly but individual cells burst at nearly every second cycle or less frequently. The active-quiescent state is not robust at all to heterogeneity or noise. Total asynchrony is observed when heterogeneity or noise is too large, e.g., even at 25% heterogeneity for our reference set of parameter values. 6. The fast GABAA inhibition (with a reversal potential more negative than, say, -65 mV) favors the cluster states and prevents full synchrony. Our simulation results suggest two mechanisms that can fully synchronize the isolated RE network model. With GABAA removed or almost totally blocked, GABAB inhibition (because it is slow) can lead to full synchrony, which is partially robust to heterogeneity and noise.(ABSTRACT TRUNCATED AT 400 WORDS)

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