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Neuronal Function
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
By altering the postsynaptic membrane permeability, the transmitter produces a local potential change resulting in either depolarization or hyperpolarization. As depolarization leads to excitation of a neuron, it is called an excitatory postsynaptic potential (EPSP). An EPSP is a depolarization of a few millivolts resulting from an increased postsynaptic membrane conductance to Na+ and K+ ions. Na+ ions move into the cell, and K+ ions move out. As the movement of Na+ ions predominates, the net effect is a small depolarization of the postsynaptic membrane, bringing the membrane potential closer to the threshold required for opening of its voltage-gated channels so that an action potential is more likely to be triggered.
Viscerotopic Representation of the Alimentary Tract in the Dorsal and Ventral Vagal Complexes in the Rat
Published in Sue Ritter, Robert C. Ritter, Charles D. Barnes, Neuroanatomy and Physiology of Abdominal Vagal Afferents, 2020
S.M. Altschuler, L. Rinaman, R.R. Miselis
The observation that vago-vagal monosynaptic contacts are located almost exclusively on distal motoneuronal dendrites in the NTSgel supports the idea that there may be a distinct organization of synaptic endings on the dendritic tree of vagal motoneurons. Even synapses made on the most distal portion of a dendrite can contribute effectively to somatic depolarization.89 Although unitary post synaptic potentials (PSPs) generated by terminals synapsing on a neuron’s distal dendrites may be of smaller amplitude when recorded at the soma than PSPs generated at more proximal locations, the spines that are present on vagal motoneuronal dendrites create irregular geometries that may cause higher local potentials for a given synaptic current. Distal synapses could have important consequences for dendritic integration, since the potential created within a dendrite could markedly change the driving force for other nearby PSPs. The peak amplitude of PSPs generated in dendrites quickly attenuates toward the soma, but the high transmission coefficient in the distal direction would lead to marked distal dendritic depolarization, and therefore significantly reduce the driving force for all distally-located PSPs on the same dendritic branch.
Advances in Understanding the Mechanisms Underlying Synaptic Plasticity
Published in Avital Schurr, Benjamin M. Rigor, BRAIN SLICES in BASIC and CLINICAL RESEARCH, 2020
Timothy J. Teyler, Idil Cavus, Chris Coussens, Pascal DiScenna, Lawrence Grover, Yi-Ping Lee, Zeb Little
The most important consequence of this model is that cytosolic calcium concentration and/or location, and not voltage dependency, is the most direct determinant of synaptic plasticity. Clearly, the postsynaptic potential contributes to synaptic plasticity since both the NMDA and VDCC channels are voltage dependent; however, the triggering event for all forms of synaptic plasticity considered here is elevated cytosolic Ca2+. It thus appears that a central question regarding synaptic plasticity is the origin of the elevation in cytosolic calcium, be it from NMDA channels, VDCCs, or intracellular stores, and the identity and function of their specific calcium binding proteins. Differences in synaptic plasticity seen in different regions of the brain may reflect differences in the expression of the receptors, enzymes, and factors responsible for the forms of synaptic plasticity reviewed here.
The impact of different dark chocolate dietary patterns on synaptic potency and plasticity in the hippocampal CA1 area of the rats under chronic isolation stress
Published in Nutritional Neuroscience, 2023
Elham Kalantarzadeh, Maryam Radahmadi, Parham Reisi
Studying the extracellular recordings of field excitatory postsynaptic potential (fEPSP) waveforms is a commonly employed technique to assess neural excitability, synaptic plasticity, and LTP. The fEPSP components (i.e. slope and amplitude) are used as the criteria for evaluating synaptic plasticity [20,21]. The fEPSP slope is defined as the slope between the baseline and peak of the negative wave. Also, their amplitude is measured as the voltage difference between the negative peak of the fEPSP wave and its baseline. Moreover, fEPSPs were first stimulated at 0.1 Hz in the CA1 area, then amplified (×1000), and band-pass filtered (1–3 kHz). Subsequently, the signals were transferred through an analogue-digital interface (ScienceBeam-D3111, eProbe Experiment software) to a computer. The obtained data were analyzed by the eTrace analysis software (Science Beam; Parto Danesh, Tehran, Iran). Moreover, the stimulus-response or Input/Output (I/O) functions were acquired to verify if the interventions had affected the basal circuity properties and synaptic potency (neural excitability) in the intended areas. Before LTP induction, a systematic variation of current (100–1000 μA) was used.
A review of a diazepam nasal spray for the treatment of acute seizure clusters and prolonged seizures
Published in Expert Review of Neurotherapeutics, 2021
Lindsay M. Higdon, Michael R. Sperling
All benzodiazepines have a similar chemical structure and mechanism of action and are differentiated by speed of onset and duration of action. Benzodiazepines bind to the GABAA receptor in neurons, thereby increasing inhibitory currents [10]. Electrophysiological studies demonstrate that benzodiazepines increased the amplitude of inhibitory post-synaptic potentials (IPSPs) by increasing the opening frequency of the GABA-gated chloride channel [11]. Duration of action is determined by the method of biotransformation and the extent of redistribution. Long-acting benzodiazepines, such as diazepam, are broken down into active metabolites, but diazepam is highly lipophilic with rapid redistribution into adipose tissue; this attribute leads to a shorter duration of action in the central nervous system than would be expected from its half-life [3,5,10].
Vanillic acid attenuates amyloid β1-40-induced long-term potentiation deficit in male rats: an in vivo investigation
Published in Neurological Research, 2021
Nesa Ahmadi, Naser Mirazi, Alireza Komaki, Samaneh Safari, Abdolkarim Hosseini
In the DG, field excitatory postsynaptic potential (fEPSP) and PS were the two components of the evoked field potentials. During the electrophysiological recordings, fEPSP slopes and alterations in the PS amplitudes were assessed. The slope functions of fEPSP were measured as the slope of the line which connects the beginning of the evoked potential’s initial positive deflection with the peak of the deflection in the second positive evoked potential. We measured the PS amplitudes from the first deflection’s peak which was positive in the evoked potential to the peak of the next potential which was negative [22,23]. The slope measurements of fEPSP were taken between 20% and 80% of the peak amplitude. In the current study, in order to evoke potentials, the adjustment of the stimulation intensity was implemented which included 40% of the maximum PS amplitude, specified by a curve of input/output [18].