Further characteristics of hippocampal CA1 cells in vitro

Background: Inflammation is a hallmark of epileptogenic brain tissue. Previously, we have shown that inflammation in epilepsy can be delineated using systemically-injected fluorescent and magnetite- laden nanoparticles. Suggested mechanisms included distribution of free nanoparticles across a compromised blood-brain barrier or their transfer by monocytes that infiltrate the epileptic brain. Objective: In the current study, we evaluated monocytes as vehicles that deliver nanoparticles into the epileptic brain. We also assessed the effect of epilepsy on the systemic distribution of nanoparticleloaded monocytes. Methods: The in vitro uptake of 300-nm nanoparticles labeled with magnetite and BODIPY (for optical imaging) was evaluated using rat monocytes and fluorescence detection. For in vivo studies we used the rat lithium-pilocarpine model of temporal lobe epilepsy. In vivo nanoparticle distribution was evaluated using immunohistochemistry. Results: 89% of nanoparticle loading into rat monocytes was accomplished within 8 hours, enabling overnight nanoparticle loading ex vivo. The dose-normalized distribution of nanoparticle-loaded monocytes into the hippocampal CA1 and dentate gyrus of rats with spontaneous seizures was 176-fold and 380-fold higher compared to the free nanoparticles (p<0.05). Seizures were associated with greater nanoparticle accumulation within the liver and the spleen (p<0.05). Conclusion: Nanoparticle-loaded monocytes are attracted to epileptogenic brain tissue and may be used for labeling or targeting it, while significantly reducing the systemic dose of potentially toxic compounds. The effect of seizures on monocyte biodistribution should be further explored to better understand the systemic effects of epilepsy.

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Factors affecting paired-pulse facilitation in hippocampal CA1 neurons in vitro

Brain Research ◽

10.1016/0006-8993(94)90209-7 ◽

1994 ◽

Vol 650 (1) ◽

pp. 75-84 ◽

Cited By ~ 57

Author(s):

L. Stan Leung ◽

Xiao-Wen Fu

Keyword(s):

Factors Affecting ◽

Ca1 Neurons ◽

Paired Pulse ◽

Paired Pulse Facilitation ◽

Hippocampal Ca1 Neurons ◽

Hippocampal Ca1

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Visfatin reduces hippocampal CA1 cells death and improves learning and memory deficits after transient global ischemia/reperfusion

Neuropeptides ◽

10.1016/j.npep.2014.12.004 ◽

2015 ◽

Vol 49 ◽

pp. 63-68 ◽

Cited By ~ 18

Author(s):

Sohaila Erfani ◽

Mehdi Khaksari ◽

Shahrbanoo Oryan ◽

Nabi Shamsaei ◽

Nahid Aboutaleb ◽

...

Keyword(s):

Learning And Memory ◽

Ischemia Reperfusion ◽

Memory Deficits ◽

Global Ischemia ◽

Hippocampal Ca1 ◽

Transient Global Ischemia ◽

Learning And Memory Deficits ◽

Cells Death ◽

Ca1 Cells

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Theta-Frequency Resonance in Hippocampal CA1 Neurons In Vitro Demonstrated by Sinusoidal Current Injection

Journal of Neurophysiology ◽

10.1152/jn.1998.79.3.1592 ◽

1998 ◽

Vol 79 (3) ◽

pp. 1592-1596 ◽

Cited By ~ 108

Author(s):

L. Stan Leung ◽

Hui-Wen Yu

Keyword(s):

Resonant Frequency ◽

Hippocampal Neurons ◽

Ca1 Neurons ◽

Frequency Resonance ◽

Hippocampal Ca1 Neurons ◽

Hippocampal Ca1 ◽

Theta Frequency ◽

Sinusoidal Current ◽

Sinusoidal Currents

Leung, L. Stan and Hui-Wen Yu. Theta-frequency resonance in hippocampal CA1 neurons in vitro demonstrated by sinusoidal current injection. J. Neurophysiol. 79: 1592–1596, 1998. Sinusoidal currents of various frequencies were injected into hippocampal CA1 neurons in vitro, and the membrane potential responses were analyzed by cross power spectral analysis. Sinusoidal currents induced a maximal (resonant) response at a theta frequency (3–10 Hz) in slightly depolarized neurons. As predicted by linear systems theory, the resonant frequency was about the same as the natural (spontaneous) oscillation frequency. However, in some cases, the resonant frequency was higher than the spontaneous oscillation frequency, or resonance was found in the absence of spontaneous oscillations. The sharpness of the resonance ( Q), measured by the peak frequency divided by the half-peak power bandwidth, increased from a mean of 0.44 at rest to 0.83 during a mean depolarization of 6.5 mV. The phase of the driven oscillations changed most rapidly near the resonant frequency, and it shifted about 90° over the half-peak bandwidth of 8.4 Hz. Similar results were found using a sinusoidal function of slowly changing frequency as the input. Sinusoidal currents of peak-to-peak intensity of >100 pA may evoke nonlinear responses characterized by second and higher harmonics. The theta-frequency resonance in hippocampal neurons in vitro suggests that the same voltage-dependent phenomenon may be important in enhancing a theta-frequency response when hippocampal neurons are driven by medial septal or other inputs in vivo.

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Activation of electrogenic sodium pump in hippocampal CA1 neurons following glutamate-induced depolarization

Journal of Neurophysiology ◽

10.1152/jn.1986.56.2.507 ◽

1986 ◽

Vol 56 (2) ◽

pp. 507-522 ◽

Cited By ~ 51

Author(s):

S. M. Thompson ◽

D. A. Prince

Keyword(s):

Pyramidal Neurons ◽

Sodium Pump ◽

Equilibrium Potential ◽

Ca1 Neurons ◽

Electrogenic Sodium Pump ◽

Hippocampal Ca1 ◽

Voltage Dependent ◽

Specific Antagonist ◽

Conductance Increase

Intracellular recordings were obtained from guinea pig hippocampal CA1 pyramidal neurons maintained in vitro. Focal applications of glutamate produced depolarizations followed by prolonged hyperpolarizations. The mechanisms underlying this postglutamate hyperpolarization (PGH) were investigated. PGH did not reverse polarity with hyperpolarization to potentials at or near the presumed K+ equilibrium potential. A transient increase in conductance was associated with the PGH; control values returned well before the termination of PGH. Application of Mn2+, an antagonist of voltage-dependent calcium conductance, blocked synaptic transmission and the afterhyperpolarization (AHP) that follows a directly evoked train of action potentials but did not diminish the PGH or the transient conductance increase. Intracellular application of the calcium chelator ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid blocked AHP but did not affect PGH. Reductions in temperature from 37 to 27-32 degrees C reduced the amplitude of PGH and prolonged its duration but increased the amplitude and duration of AHP. The transient conductance increase associated with PGH was unaffected. Application of strophanthidin, a specific antagonist of Na+-K+-ATPase, reversibly blocked PGH and led to large increases in the amplitude and duration of the AHP. It is concluded that PGH is produced by activation of the electrogenic sodium pump by glutamate-induced excitation. As such, PGH is a useful physiological assay of electrogenic sodium transport. In addition, maintenance of the Na+ gradient by the sodium pump is important for the buffering of Ca2+ influx.

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Membrane Dysfunction Induced by In Vitro Ischemia in Rat Hippocampal CA1 Pyramidal Neurons

Journal of Neurophysiology ◽

10.1152/jn.1999.81.4.1872 ◽

1999 ◽

Vol 81 (4) ◽

pp. 1872-1880 ◽

Cited By ~ 42

Author(s):

E. Tanaka ◽

S. Yamamoto ◽

H. Inokuchi ◽

T. Isagai ◽

H. Higashi

Keyword(s):

Membrane Potential ◽

Voltage Clamp ◽

Pyramidal Neurons ◽

Membrane Surface ◽

Bathing Medium ◽

Ca1 Pyramidal Neurons ◽

In Vitro Ischemia ◽

Hippocampal Ca1 ◽

Electrode Voltage

Membrane dysfunction induced by in vitro ischemia in rat hippocampal CA1 pyramidal neurons. Intracellular and single-electrode voltage-clamp recordings were made to investigate the process of membrane dysfunction induced by superfusion with oxygen and glucose-deprived (ischemia-simulating) medium in hippocampal CA1 pyramidal neurons of rat tissue slices. To assess correlation between potential change and membrane dysfunction, the recorded neurons were stained intracellularly with biocytin. A rapid depolarization was produced ∼6 min after starting superfusion with ischemia-simulating medium. When oxygen and glucose were reintroduced to the bathing medium immediately after generating the rapid depolarization, the membrane did not repolarize but depolarized further, the potential reaching 0 mV ∼5 min after the reintroduction. In single-electrode voltage-clamp recording, a corresponding rapid inward current was observed when the membrane potential was held at −70 mV. After the reintroduction of oxygen and glucose, the current induced by ischemia-simulating medium partially returned to preexposure levels. These results suggest that the membrane depolarization is involved with the membrane dysfunction. The morphological aspects of biocytin-stained neurons during ischemic exposure were not significantly different from control neurons before the rapid depolarization. On the other hand, small blebs were observed on the surface of the neuron within 0.5 min of generating the rapid depolarization, and blebs increased in size after 1 min. After 3 min, neurons became larger and swollen. The long and transverse axes and area of the cross-sectional cell body were increased significantly 1 and 3 min after the rapid depolarization. When Ca2+-free (0 mM) with Co2+ (2.5 mM)-containing medium including oxygen and glucose was applied within 1 min after the rapid depolarization, the membrane potential was restored completely to the preexposure level in the majority of neurons. In these neurons, the long axis was lengthened without any blebs being apparent on the membrane surface. These results suggest that the membrane dysfunction induced by in vitro ischemia may be due to a Ca2+-dependent process that commences ∼1.5 min after and is completed 3 min after the onset of the rapid depolarization. Because small blebs occurred immediately after the rapid depolarization and large blebs appeared 1.5–3 min after, it is likely that the transformation from small to large blebs may result in the observed irreversible membrane dysfunction.

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