Enhancement of Whole Cell Synaptic Currents by Low Osmolarity and by Low [NaCl] in Rat Hippocampal Slices

1997 ◽  
Vol 77 (5) ◽  
pp. 2349-2359 ◽  
Author(s):  
Rong Huang ◽  
Daniel F. Bossut ◽  
George G. Somjen
Keyword(s):  
Synaptic Transmission ◽  
Time Constant ◽  
Hippocampal Slices ◽  
Input Resistance ◽  
Tissue Slices ◽  
Synaptic Currents ◽  
Whole Cell ◽  
Input Capacitance ◽  
Postsynaptic Currents ◽  
Inward Currents

Huang, Rong, Daniel F. Bossut, and George G. Somjen. Enhancement of whole cell synaptic currents by low osmolarity and by low [NaCl] in rat hippocampal slices. J. Neurophysiol. 77: 2349–2359, 1997. We recorded whole cell currents of patch-clamped neurons in stratum pyramidale of CA1 region of rat hippocampal tissue slices. Synaptic currents were evoked by orthodromic stimulation while holding potential of the neuron was varied from hyperpolarized to depolarized levels. Extracellular osmolarity (πo) was lowered by superfusion with artificial cerebrospinal fluid in which NaCl concentration ([NaCl]) was reduced. The effect of low extracellular NaCl was tested in additional trials in which NaCl was substituted by isosmolar fructose. Both lowering of πo and isosmotic lowering of extracellular [NaCl] ([NaCl]o) caused reversible increase of excitatory postsynaptic currents. The effect of lowering πo was concentration dependent, and it was significantly stronger than the effect of equivalent isosmotic lowering of [NaCl]o. Inhibitory postsynaptic currents also increased in many but not in all cases. Lowering of πo caused a prolongation of the time constant of relaxation of the capacitive charging current induced by small hyperpolarizing voltage steps. A virtual input capacitance, calculated by dividing this time constant by the input resistance, increased during hypotonic exposure. Isosmotic lowering of [NaCl]o had no effect on time constant or input capacitance. Depolarizing voltage commands evoked spikelike inward currents presumably representing Na+-dependent action potentials generated outside the voltage-clamped region of the cell. These current spikes became smaller in low πo and in low [NaCl]o. Broader, voltage-dependent, presumably Ca2+-mediated inward currents became more prominent during hypotonic exposure. We conclude that lowering of [NaCl]o causes enhancement of excitatory synaptic transmission. Transmission may be facilitated by the uptake of Ca2+ into presynaptic terminals as well as into postsynaptic target neurons, induced by the low [NaCl]o. Lowering of πo enhances synaptic transmission more than does a corresponding isosmotic lowering of [NaCl]. The excess increase recorded from the cell soma in low πo may in part be due to changing electrotonic length caused by the swelling of dendrites.

Two Mechanisms That Raise Free Intracellular Calcium in Rat Hippocampal Neurons During Hypoosmotic and Low NaCl Treatment

2000 ◽  
Vol 83 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Aren J. Borgdorff ◽  
George G. Somjen ◽  
Wytse J. Wadman
Keyword(s):  
Synaptic Transmission ◽  
Intracellular Calcium ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Cell Swelling ◽  
Tissue Slices ◽  
Extracellular Medium ◽  
Calcium Activity ◽  
Hippocampal Pyramidal Neurons

Previous studies have shown that exposing hippocampal slices to low osmolarity (πo) or to low extracellular NaCl concentration ([NaCl]o) enhances synaptic transmission and also causes interstitial calcium ([Ca2+]o) to decrease. Reduction of [Ca2+]o suggests cellular uptake and could explain the potentiation of synaptic transmission. We measured intracellular calcium activity ([Ca2+]i) using fluorescent indicator dyes. In CA1 hippocampal pyramidal neurons in tissue slices, lowering πo by ∼70 mOsm caused “resting” [Ca2+]i as well as synaptically or directly stimulated transient increases of calcium activity (Δ[Ca2+]i) to transiently decrease and then to increase. In dissociated cells, lowering πo by ∼70 mOsm caused [Ca2+]i to almost double on average from 83 to 155 nM. The increase of [Ca2+]i was not significantly correlated with hypotonic cell swelling. Isoosmotic (mannitol- or sucrose-substituted) lowering of [NaCl]o, which did not cause cell swelling, also raised [Ca2+]i. Substituting NaCl with choline-Cl or Na-methyl-sulfate did not affect [Ca2+]i. In neurons bathed in calcium-free medium, lowering πo caused a milder increase of [Ca2+]i, which was correlated with cell swelling, but in the absence of external Ca2+, isotonic lowering of [NaCl]o triggered only a brief, transient response. We conclude that decrease of extracellular ionic strength (i.e., in both low πo and low [NaCl]o) causes a net influx of Ca2+ from the extracellular medium whereas cell swelling, or the increase in membrane tension, is a signal for the release of Ca2+ from intracellular stores.

Anoxia produces smaller changes in synaptic transmission, membrane potential, and input resistance in immature rat hippocampus

1989 ◽  
Vol 62 (4) ◽  
pp. 882-895 ◽  
Author(s):  
E. Cherubini ◽  
Y. Ben-Ari ◽  
K. Krnjevic
Keyword(s):  
Synaptic Transmission ◽  
Hippocampal Slices ◽  
Mossy Fibers ◽  
Input Resistance ◽  
Resting Potential ◽  
Inward Rectification ◽  
Adult Rats ◽  
Ca1 Neurons ◽  
Postsynaptic Potentials ◽  
Ca3 Neurons

1. The reversible blocking effect of brief anoxia (2-4 min) on synaptic transmission was studied in submerged hippocampal slices (kept mostly at 34 degrees), obtained from adult (greater than 120 g) and very young (6-50 g) Wistar rats. Excitatory postsynaptic potentials (EPSPs) were recorded with extra- and intracellular electrodes, sometimes simultaneously: in CA1, they were evoked by stratum radiation stimulation, in CA3 by hilar stimulation. 2. In slices from adults, EPSPs in CA1 were depressed by 90% after 2 min of anoxia, and postanoxic recovery was relatively slow (one-half recovery times 4.0 +/- 0.23 min, mean +/- SE). EPSPs in CA3 were consistently more resistant, especially those generated by mossy fibers; after 2 min of anoxia, these were reduced by only 14.7 +/- 5.4%. 3. In newborn animals (PN1-4), both intra- and extracellular EPSPs (but no population spikes) could be recorded in CA1. Although smaller and more fatigable than in the adult, they were much more resistant to anoxia, after 2 min being reduced by only 44.1 +/- 8.8%; and they were not abolished even after 6-7 min. On the other hand, postanoxic recovery was very rapid, being one-half complete in 2.4 +/- 0.48 min. Only large and very prolonged (giant) depolarizing PSPs [probably inhibitory postsynaptic potentials (IPSPs)] could be recorded in CA3 neurons; they were rapidly blocked by anoxia. 4. In older pups (PN6-21), the CA1 EPSPs became progressively more sensitive to anoxia. At the end of the second week, they were as rapidly blocked as in slices from adults; but postanoxic recovery remained quicker throughout this period. In CA3, EPSPs could now be evoked that were as resistant to anoxia as in adult slices. 5. In both CA1 and CA3 neurons from adult rats, anoxia (for 2-3 min) reduced the input resistance (RN) by 45.7 +/- 6.25%. In CA1 neurons, there was most often some hyperpolarization (-7.2 +/- 1.8 mV), which was less consistent in CA3 cells. The return of O2 typically led to a second (postanoxic) phase of hyperpolarization (-7.9 +/- 1.93 mV). 6. At PN1-4, the resting potential (Vm) of most cells had to be maintained by current injection; the input resistance (RN) of CA1 neurons was 70% higher than in mature cells, and there was little time-dependent inward rectification. Anoxia produced no regular changes in Vm, and reductions in RN were very small (by only 9.6 +/- 5.0%). A postanoxic hyperpolarization was seen in only 2 neurons out of 11.(ABSTRACT TRUNCATED AT 400 WORDS)

Heptanol But Not Fluoroacetate Prevents the Propagation of Spreading Depression in Rat Hippocampal Slices

1997 ◽  
Vol 77 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Carlota Largo ◽  
Geoffrey C. Tombaugh ◽  
Peter G. Aitken ◽  
Oscar Herreras ◽  
George G. Somjen
Keyword(s):  
Synaptic Transmission ◽  
Gap Junctions ◽  
Spreading Depression ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Lipid Phase ◽  
Tissue Slices ◽  
Population Spikes ◽  
Afferent Volleys ◽  
Stimulation Of

Largo, Carlota, Geoffrey C. Tombaugh, Peter G. Aitken, Oscar Herreras, and George G. Somjen. Heptanol but not fluoroacetate prevents the propagation of spreading depression in rat hippocampal slices. J. Neurophysiol. 77: 9–16, 1997. We investigated whether heptanol and other long-chain alcohols that are known to block gap junctions interfere with the generation or the propagation of spreading depression (SD). Waves of SD were triggered by micro-injection of concentrated KCl solution in stratum (s.) radiatum of CA1 of rat hippocampal tissue slices. DC-coupled recordings of extracellular potential ( V o) were made at the injection and at a second site ∼1 mm distant in st. radiatum and sometimes also in st. pyramidale. Extracellular excitatory postsynaptic potentials (fEPSPs) were evoked by stimulation of the Schaffer collateral bundle; in some experiments, antidromic population spikes were evoked by stimulation of the alveus. Bath application of 3 mM heptanol or 5 mM hexanol completely and reversibly prevented the propagation of the SD-related potential shift (Δ V o) without abolishing the Δ V o at the injection site. Octanol (1 mM) had a similar but less reliably reversible effect. fEPSPs were depressed by ∼30% by heptanol and octanol, 65% by hexanol. Antidromic population spikes were depressed by 30%. In isolated, patch-clamped CA1 pyramidal neurons, heptanol partially and reversibly depressed voltage-dependent Na currents possibly explaining the slight depression of antidromic spikes and, by acting on presynaptic action potentials, also the depression of fEPSPs. Fluoroacetate (FAc), a putative selective blocker of glial metabolism, first induced multiple spike firing in response to single afferent volleys and then severely suppressed synaptic transmission (confirming earlier reports) without depressing the antidromic population spike. FAc did not inhibit SD propagation. The effect of alkyl alcohols is compatible with the idea that the opening of normally closed neuronal gap junctions is required for SD propagation. Alternative possible explanations include interference with the lipid phase of neuron membranes. The absence of SD inhibition by FAc confirms that synaptic transmission is not necessary for the propagation of SD, and it suggests that normally functioning glial cells are not essential for SD generation or propagation.

Effects of Hyposmolar Solutions on Membrane Currents of Hippocampal Interneurons and Mossy Cells In Vitro

1998 ◽  
Vol 79 (2) ◽  
pp. 1108-1112 ◽  
Author(s):  
Scott C. Baraban ◽  
Philip A. Schwartzkroin
Keyword(s):  
Voltage Clamp ◽  
Hippocampal Slices ◽  
Cell Voltage ◽  
Potassium Currents ◽  
Membrane Currents ◽  
Excitatory Postsynaptic Currents ◽  
Whole Cell ◽  
Mossy Cells ◽  
Postsynaptic Currents

Baraban, Scott C. and Philip A. Schwartzkroin. Effects of hyposmolar solutions on membrane currents of hippocampal interneurons and mossy cells in vitro. J. Neurophysiol. 79: 1108–1112, 1998. Whole cell voltage-clamp recordings in rat hippocampal slices were used to investigate the effect of changes in extracellular osmolarity on voltage-activated potassium currents. Currents were evoked from oriens/alveus (O/A) interneurons, hilar interneurons, and mossy cells. Hyposmolar external solutions produced a significant potentiation of K+ current recorded from O/A and hilar interneurons, but not from mossy cells. Hyposmolar solutions also dramatically potentiated the spontaneous excitatory postsynaptic currents recorded from mossy cells. These results suggest that hippocampal excitability can be modulated by the complex actions exerted by changes in extracellular osmolarity.

Membrane Potential of CA3 Hippocampal Pyramidal Cells During Postnatal Development

2003 ◽  
Vol 90 (5) ◽  
pp. 2964-2972 ◽  
Author(s):  
Roman Tyzio ◽  
Anton Ivanov ◽  
Cristophe Bernard ◽  
Gregory L. Holmes ◽  
Yehezkiel Ben-Ari ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Postnatal Development ◽  
Developmental Change ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Input Resistance ◽  
Whole Cell ◽  
Perforated Patch ◽  
Ca3 Pyramidal Cells ◽  
Whole Cell Recordings

A depolarized resting membrane potential has long been considered to be a universal feature of immature neurons. Despite the physiological importance, the underlying mechanisms of this developmental phenomenon are poorly understood. Using perforated-patch, whole cell, and cell-attached recordings, we measured the membrane potential in CA3 pyramidal cells in hippocampal slices from postnatal rats. With gramicidin perforated-patch recordings, membrane potential was –44 ± 4 (SE) mV at postnatal days P0–P2, and it progressively shifted to –67 ± 2 mV at P13–15. A similar developmental change of the membrane potential has been also observed with conventional whole cell recordings. However, the value of the membrane potential deduced from the reversal potential of N-methyl-d-aspartate channels in cell-attached recordings did not change with age and was –77 ± 2 mV at P2 and –77 ± 2 mV at P13–14. The membrane potential measured using whole cell recordings correlated with seal and input resistance, being most depolarized in neurons with high, several gigaohms, input resistance and low seal resistance. Simulations revealed that depolarized values of the membrane potential in whole cell and perforated-patch recordings could be explained by a shunt through the seal contact between the pipette and membrane. Thus the membrane potential of CA3 pyramidal cells appears to be strongly negative at birth and does not change during postnatal development.

scholarly journals Effect of Barbiturates on Synaptic Currents

1976 ◽  
Vol 4 (3) ◽  
pp. 199-202 ◽  
Author(s):  
T. A. Torda ◽  
P. W. Gage
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neuromuscular Junction ◽  
Synaptic Transmission ◽  
Time Constant ◽  
Mode Of Action ◽  
Synaptic Currents ◽  
End Plate ◽  
The Central Nervous System ◽  
Central Synapses

Thiopentone and pentobarbitone reduce the time constant of decay of miniature end-plate currents when applied in anaesthetic concentrations to the neuromuscular junction. Such an effect at central synapses would lead to failure of synaptic transmission in the central nervous system and may reflect a common mode of action of many anaesthetic drugs.

Measurement of passive membrane parameters with whole-cell recording from neurons in the intact amphibian retina

1989 ◽  
Vol 61 (1) ◽  
pp. 218-230 ◽  
Author(s):  
P. A. Coleman ◽  
R. F. Miller
Keyword(s):  
Time Constant ◽  
Ganglion Cells ◽  
Dendritic Tree ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Retinal Neurons ◽  
Whole Cell ◽  
Cell Recording ◽  
Tryptic Activity ◽  
Specific Membrane

1. Whole-cell recordings have been obtained from intact, photoactive retinal neurons using patch-clamp electrodes in the amphibian superfused retina eyecup preparation. 2. After removal of the vitreous humor from the surface of the retina, using a collagenase with low tryptic activity, high-resistance seals (1-10 G omega) could be formed between the patch pipette and the cell membrane by applying mild suction to the pipette. Additional suction broke the membrane patch and provided continuity between the low-resistance pipette and the interior of the neuron. 3. Measurements of input resistance and time constant were obtained from bipolar, amacrine, and ganglion cells. Assuming the membrane capacitance was 1 microF/cm2, time constant data were used to derive the specific membrane resistance. The average specific membrane resistance for the inner retinal neurons in our sample was 68,000 omega.cm2. 4. Analysis of the charging curve induced by a brief current pulse applied to the soma was used to analyze the average electrotonic length of dendrites. The charging curves of some ganglion cells were well represented by a single exponential, suggesting that they were essentially isopotential. 5. The voltage decay along an equivalent cylinder model of a ganglion cell was calculated, using the experimentally obtained values of membrane resistance to compute decay of steady-state voltages along the dendritic tree. The calculations indicate that with the high membrane resistance values implied by this study, the electrotonic length of dendritic cables were short, and there may be relatively little attenuation of the synaptic potentials irrespective of their location along the dendritic tree.

Whole-cell and single-channel recordings of GABA-gated currents in cultured chick cerebral neurons

1988 ◽  
Vol 59 (2) ◽  
pp. 495-513 ◽  
Author(s):  
D. S. Weiss ◽  
E. M. Barnes ◽  
J. J. Hablitz
Keyword(s):  
Membrane Potential ◽  
Time Constant ◽  
Exponential Function ◽  
Single Channel ◽  
Synaptic Currents ◽  
Whole Cell ◽  
Cerebral Neurons ◽  
Single Exponential Function ◽  
Single Exponential ◽  
Conductance State

1. gamma-Aminobutyric acid (GABA) (10-500 microM) was applied to cultured chick cerebral neurons by pressure ejection, and the resulting currents (IGABA) were recorded using standard whole-cell voltage-clamp techniques. Plots of the peak IGABA as a function of membrane potential were nonlinear with an outwardly rectifying appearance. 2. IGABA decayed during a prolonged application of GABA. This decay was associated with a decline in the conductance of the cell, suggesting that the decline in IGABA was principally due to receptor desensitization. 3. After 5-7 days in culture, whole-cell recordings revealed the presence of spontaneous synaptic currents. These currents were presumed to be GABA-gated inhibitory postsynaptic currents (IPSCs) because they reversed at the Cl- equilibrium potential (ECl-), were blocked by picrotoxin (25 microM), and were prolonged by pentobarbital (50 microM). 4. Synaptic currents were analyzed by fitting exponential functions to their decay. In normal recording saline, 68% of the decays analyzed could be adequately described by a single exponential function. Two exponentials were necessary to describe the decay of the other 32%. The time constant of the decay (for those adequately fitted by a single exponential) increased with depolarization, from an average value of 15 ms at -80 mV to 60 ms at +40 mV. 5. A relationship was noted between IPSC amplitude and decay time constant; IPSCs with larger peak amplitudes had a slower decay. One possible explanation considered for this finding was that transmitter persists in the synaptic cleft and rebinds to the receptors, thus prolonging the decay of the IPSC. 6. Consistent with the above hypothesis was the observation that the decays of miniature IPCSs (examined under conditions of reduced transmitter release) were faster, showed less variability, and were all adequately described by a single exponential function. Furthermore, the decay times were independent of the membrane potential, suggesting that the kinetic parameters of the GABA channel which shape the decay of these miniature IPSCs are independent of voltage. 7. Single-channel activity underlying whole-cell GABA responses could be recorded in isolated outside-out and inside-out patches of membrane. In isotonic choline chloride, single-channel amplitudes were linearly related to voltage and reversed at -1.8 +/- 11.0 mV (n = 12). Under these conditions, the channel had a main conductance state of 20.8 +/- 3.4 pS (n = 12). Transitions were observed from this main conductance state to other conductance states, e.g., two subconductance states of 6 and 12 pS and one supraconductance state of 30 pS.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals ALLN rescues an in vitro excitatory synaptic transmission deficit in Lis1 mutant mice

2013 ◽  
Vol 109 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Joy Y. Sebe ◽  
Marina Bershteyn ◽  
Shinji Hirotsune ◽  
Anthony Wynshaw-Boris ◽  
Scott C. Baraban
Keyword(s):  
Synaptic Transmission ◽  
Neuronal Migration ◽  
Therapeutic Potential ◽  
Hippocampal Slices ◽  
In Utero ◽  
Mutant Mice ◽  
Excitatory Synaptic Transmission ◽  
Calpain Inhibitor ◽  
Tissue Slices ◽  
Littermate Control

LIS1 gene mutations lead to a rare neurological disorder, classical lissencephaly, characterized by brain malformations, mental retardation, seizures, and premature death. Mice heterozygous for Lis1 ( Lis1+/−) exhibit cortical malformations, defects in neuronal migration, increased glutamate-mediated synaptic transmission, and spontaneous electrographic seizures. Recent work demonstrated that in utero treatment of Lis1+/− mutant dams with ALLN, a calpain inhibitor, partially rescues neuronal migration defects in the offspring. Given the challenges of in utero drug administration, we examined the therapeutic potential of ALLN on postnatal lissencephalic cells. Voltage- and current-clamp studies were performed with acute hippocampal slices obtained from Lis1 mutant mice and age-matched littermate control mice. Specifically, we determined whether postnatal ALLN treatment can reverse excitatory synaptic transmission deficits, namely, an increase in spontaneous and miniature excitatory postsynaptic current (EPSC) frequency, on CA1 pyramidal neurons observed in tissue slices from Lis1+/− mice. We found that acute application of ALLN restored spontaneous and miniature EPSC frequencies to wild-type levels without affecting inhibitory postsynaptic synaptic current. Furthermore, Western blot analysis of protein expression, including proteins involved in excitatory synaptic transmission, demonstrated that ALLN blocks the cleavage of the calpain substrate αII-spectrin but does not rescue Lis1 protein levels in Lis1+/− mutants.

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