Large Inhibitory Postsynaptic Potentials Evoked in Hippocampal Neurons by 4-Aminopyridine

2015 ◽  
pp. 157-167
Author(s):  
Menahem Segal
Keyword(s):  
Hippocampal Neurons ◽  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials

Electrophysiological evidence from glutamate microapplications for local excitatory circuits in the CA1 area of rat hippocampal slices

1988 ◽  
Vol 59 (1) ◽  
pp. 110-123 ◽  
Author(s):  
E. P. Christian ◽  
F. E. Dudek
Keyword(s):  
Hippocampal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Inhibitory Synapses ◽  
Excitatory Synapses ◽  
Recording Site ◽  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials ◽  
Ca1 Area ◽  
Transverse Slice

1. Evidence for local excitatory synaptic connections in CA1 of the rat hippocampus was obtained by recording excitatory postsynaptic potentials (EPSPs) intracellularly from pyramidal cells during local microapplications of glutamate. 2. Experiments were performed in hippocampal slices cut parallel to (transverse slice) or perpendicular to (longitudinal slice) alvear fibers. In normal solutions, glutamate microdrops (10–20 mM, 10–20 micron diam) applied in CA1 within 400 micron of recorded cells sometimes increased the frequency of inhibitory postsynaptic potentials for 5–10 s in both transverse and longitudinal slices. Increases in EPSP frequency were also occasionally observed, but only in transverse slices. Tetrodotoxin (1 microgram/ml) blocked glutamate-induced increases in PSP frequency, thus indicating that they were not caused by subthreshold effects on presynaptic terminals. Increases in PSP frequency were interpreted to result from glutamate activation of hippocampal neurons with inhibitory and excitatory connections to recorded neurons. 3. In both slice orientations, local excitatory circuits were studied in more isolated conditions by surgically separating CA1 from CA3 (transverse slices) and by blocking GABAergic inhibitory synapses with picrotoxin (5–10 microM). Microdrops were systematically applied at 200 and 400 micron on each side of the recording site. Significant glutamate-induced increases in EPSP frequency were observed in neurons from both slice orientations to microdrops in at least one of the locations. This provided evidence that excitatory synapses are present in both transverse and longitudinal slices. 4. Substantial increases in EPSP frequency only occurred in neurons from longitudinal slices when glutamate was microapplied 200 micron or less from the recording site. In transverse slices, however, large increases in EPSP frequency were observed to glutamate microapplications at 200 or 400 micron. These data suggest that CA1 local excitatory connections project for longer distances in the transverse than in the longitudinal plane of section. 5. Increases in EPSP frequency, averaged across cells, did not differ significantly in the four microapplication sites in either transverse or longitudinal slices. Thus local excitation in CA1 does not appear to be asymmetrically arranged in the way suggested for CA3. 6. The densities of local excitatory circuits in CA1 versus CA3 were studied by quantitatively comparing glutamate-induced increases in EPSP frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Deoxyglucose–Induced Long-Term Potentiation of Monosynaptic IPSPs in CA1 Hippocampal Neurons

2000 ◽  
Vol 83 (2) ◽  
pp. 879-887 ◽  
Author(s):  
Krešimir Krnjević ◽  
Yong-Tao Zhao
Keyword(s):  
Hippocampal Neurons ◽  
Long Term Potentiation ◽  
Inhibitory Synapses ◽  
Current Clamp ◽  
Glutamate Antagonists ◽  
Postsynaptic Potentials ◽  
Postsynaptic Currents ◽  
Inhibitory Postsynaptic Potentials ◽  
Term Potentiation

In previous experiments on excitatory synaptic transmission in CA1, temporary (10–20 min) replacement of glucose with 10 mM 2-deoxyglucose (2-DG) consistently caused a marked and very sustained potentiation (2-DG LTP). To find out whether 2-DG has a similar effect on inhibitory synapses, we recorded pharmacologically isolated mononosynaptic inhibitory postsynaptic potentials (IPSPs; under current clamp) and inhibitory postsynaptic currents (IPSCs; under voltage clamp); 2-DG was applied both in the presence and the absence of antagonists of N-methyl-d-aspartate (NMDA). In spite of sharply varied results (some neurons showing large potentiation, lasting for >1 h, and many little or none), overall there was a significant and similar potentiation of IPSP conductance, both for the early (at ≈30 ms) and later (at ≈140 ms) components of IPSPs or IPSCs: by 35.1 ± 10.25% (mean ± SE; for n = 24, P = 0.0023) and 36.5 ± 16.3% (for n = 19, P = 0.038), respectively. The similar potentiation of the early and late IPSP points to a presynaptic mechanism of LTP. Overall, the LTP was statistically significant only when 2-DG was applied in the absence of glutamate antagonists. Tetanic stimulations (in presence or absence of glutamate antagonists) only depressed IPSPs (by half). In conclusion, although smaller and more variable, 2-DG–induced LTP of inhibitory synapses appears to be broadly similar to the 2-DG–induced LTP of excitatory postsynaptic potentials previously observed in CA1.

Valproate enhances inhibitory postsynaptic potentials in hippocampal neurons in vitro

1987 ◽  
Vol 435 (1-2) ◽  
pp. 213-219 ◽  
Author(s):  
Uli Preisendörfer ◽  
Marc L. Zeise ◽  
Manfred R. Klee
Keyword(s):  
Hippocampal Neurons ◽  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials

scholarly journals Postnatal development of synaptic properties of the GABAergic projection from the inferior colliculus to the auditory thalamus

2013 ◽  
Vol 109 (12) ◽  
pp. 2866-2882 ◽  
Author(s):  
Yamini Venkataraman ◽  
Edward L Bartlett
Keyword(s):  
Inferior Colliculus ◽  
Temporal Processing ◽  
Brain Slices ◽  
Critical Time ◽  
Membrane Properties ◽  
Auditory Temporal Processing ◽  
Postsynaptic Potentials ◽  
Auditory Thalamus ◽  
Inhibitory Postsynaptic Potentials ◽  
Medial Geniculate

The development of auditory temporal processing is important for processing complex sounds as well as for acquiring reading and language skills. Neuronal properties and sound processing change dramatically in auditory cortex neurons after the onset of hearing. However, the development of the auditory thalamus or medial geniculate body (MGB) has not been well studied over this critical time window. Since synaptic inhibition has been shown to be crucial for auditory temporal processing, this study examined the development of a feedforward, GABAergic connection to the MGB from the inferior colliculus (IC), which is also the source of sensory glutamatergic inputs to the MGB. IC-MGB inhibition was studied using whole cell patch-clamp recordings from rat brain slices in current-clamp and voltage-clamp modes at three age groups: a prehearing group [ postnatal day (P)7–P9], an immediate posthearing group (P15–P17), and a juvenile group (P22–P32) whose neuronal properties are largely mature. Membrane properties matured substantially across the ages studied. GABAA and GABAB inhibitory postsynaptic potentials were present at all ages and were similar in amplitude. Inhibitory postsynaptic potentials became faster to single shocks, showed less depression to train stimuli at 5 and 10 Hz, and were overall more efficacious in controlling excitability with age. Overall, IC-MGB inhibition becomes faster and more precise during a time period of rapid changes across the auditory system due to the codevelopment of membrane properties and synaptic properties.

Inhibitory Postsynaptic Potentials

2010 ◽  
pp. 641-645
Author(s):  
Marilyn E. Carroll ◽  
Peter A. Santi ◽  
Joseph Zohar ◽  
Thomas R. E. Barnes ◽  
Peter Verheart ◽  
...  
Keyword(s):  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials
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