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Excitatory postsynaptic potential

An excitatory postsynaptic potential (EPSP) is a transient depolarization of the postsynaptic neuron's membrane potential that increases the probability of generating an action potential, resulting from the influx of positively charged ions through ligand-gated ion channels activated by excitatory neurotransmitters.^[1] In the central nervous system, EPSPs are primarily mediated by the neurotransmitter glutamate, which is released from the presynaptic terminal and binds to ionotropic glutamate receptors on the postsynaptic membrane, such as AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartate) receptors.^[1] AMPA receptors drive the rapid, initial phase of the EPSP by permitting sodium (Na⁺) influx and potassium (K⁺) efflux through non-selective cation channels, while NMDA receptors contribute a slower, prolonged component that is voltage-dependent and highly permeable to calcium (Ca²⁺), requiring both glutamate binding and postsynaptic depolarization to relieve a magnesium (Mg²⁺) block.^[2]^[3] This ionic mechanism shifts the membrane potential from its typical resting value of approximately -60 to -70 mV toward a reversal potential near 0 mV, which exceeds the action potential threshold of about -40 to -50 mV, thereby facilitating neuronal excitation.^[1] EPSPs differ fundamentally from inhibitory postsynaptic potentials (IPSPs), which hyperpolarize the membrane via chloride (Cl⁻) influx or potassium efflux to reduce firing likelihood; instead, EPSPs integrate through spatial and temporal summation across multiple synapses to determine overall postsynaptic excitability.^[1]^[4] In physiological contexts, EPSPs underpin excitatory synaptic transmission in diverse neural circuits, from sensory processing to motor control, and are essential for activity-dependent plasticity, including long-term potentiation (LTP), where NMDA receptor activation leads to Ca²⁺-dependent signaling cascades that strengthen synaptic efficacy over time.^[3]^[2] Disruptions in EPSP generation, such as through receptor dysregulation, are implicated in neurological disorders like epilepsy and Alzheimer's disease, highlighting their critical role in brain function.^[3]

Overview

Definition

An excitatory postsynaptic potential (EPSP) is a transient depolarization of the postsynaptic membrane in a neuron, triggered by the release of excitatory neurotransmitters from a presynaptic neuron, which increases the likelihood that the postsynaptic neuron will generate an action potential.^[1] This local change in membrane potential arises from the binding of neurotransmitters to ligand-gated ion channels on the postsynaptic membrane, allowing the influx of positively charged cations.^[1] Biophysically, the EPSP results primarily from the influx of sodium ions (Na⁺) and, in some cases, calcium ions (Ca²⁺) through these channels, which shifts the membrane potential from its typical resting state of approximately -70 mV toward the action potential threshold of around -55 mV.^[5]^[6]^[7] The net positive charge entry reduces the membrane's hyperpolarization, but the magnitude of this depolarization is graded, depending on the number of activated channels and the strength of the synaptic input.^[1] Unlike the all-or-nothing nature of action potentials, EPSPs are local events that passively decay in amplitude with distance from the synapse and over time due to membrane leakage and cable properties of the neuron.^[1] This graded characteristic allows multiple EPSPs to summate spatially and temporally to reach threshold. The concept of the EPSP was first described in the 1950s through intracellular recordings from spinal motoneurons, pioneered by John C. Eccles and colleagues, who demonstrated these depolarizing synaptic potentials in response to excitatory inputs.^[8]

Physiological Role

Excitatory postsynaptic potentials (EPSPs) serve as the primary mechanism for excitatory synaptic transmission within the central nervous system (CNS), facilitating the propagation of signals across neural networks involved in sensory processing and motor control. In sensory pathways, EPSPs enable the integration of afferent inputs to generate perceptual representations, while in motor circuits, they contribute to the coordinated activation of efferent neurons for movement initiation.^[9] This depolarizing response increases the likelihood of action potential generation in the postsynaptic neuron, thereby supporting the overall excitability of neural ensembles.^[10] A key physiological function of EPSPs is their role in temporal and spatial summation, allowing postsynaptic neurons to integrate multiple synaptic inputs over time and space to determine whether the membrane potential reaches the threshold for firing.^[4] Temporal summation occurs when repeated EPSPs from the same presynaptic neuron accumulate, whereas spatial summation involves concurrent inputs from multiple presynaptic sources, enabling efficient neural computation and decision-making in complex circuits.^[9] These processes ensure that weak individual signals can collectively drive neuronal output, optimizing information flow in the CNS. EPSPs are essential for synaptic plasticity mechanisms such as long-term potentiation (LTP), which strengthens synaptic efficacy and underlies learning and memory formation.^[11] In hippocampal circuits, LTP of EPSPs supports spatial navigation by enhancing the representation of environmental cues in place cells.^[12] Similarly, in cortical excitatory networks, EPSPs facilitate perceptual processing through feature integration and synchronization, as seen in visual cortex pathways where they promote reliable transmission for sensory discrimination.^[13]

Mechanisms

Neurotransmitters and Receptors

In the vertebrate central nervous system (CNS), glutamate serves as the primary excitatory neurotransmitter, released from presynaptic terminals to bind ionotropic glutamate receptors on the postsynaptic membrane, thereby initiating excitatory postsynaptic potentials (EPSPs).^[14] This amino acid accounts for the majority of fast synaptic excitation in the brain, with its release triggered by action potentials and subsequent calcium influx in presynaptic neurons.^[15] Glutamate primarily activates three subtypes of ionotropic receptors: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA), and kainate receptors. AMPA receptors mediate rapid EPSPs by permitting sodium ion influx, typically within milliseconds, and are essential for the initial depolarization phase of synaptic transmission.^[16] In contrast, NMDA receptors contribute to slower, voltage-dependent EPSPs, involving both sodium and calcium ion entry, which requires prior depolarization to relieve magnesium blockade and plays a key role in synaptic plasticity.^[17] Kainate receptors, though less abundant, also support excitatory transmission, often modulating presynaptic release or contributing to postsynaptic responses in specific circuits.^[15] Beyond glutamate, acetylcholine acts as an excitatory neurotransmitter at neuromuscular junctions in vertebrates, where it binds to nicotinic acetylcholine receptors—ligand-gated cation channels that depolarize skeletal muscle fibers to trigger contraction.^[18] In the CNS, excitatory effects from monoamines such as serotonin or norepinephrine occur in specific contexts, like modulating cortical or hippocampal excitability through G-protein-coupled receptors that can enhance postsynaptic responses.^[19] Species variations highlight glutamate's dominance in vertebrate excitatory signaling, while acetylcholine predominates in certain invertebrate systems, such as the neuromuscular junctions and central synapses of Aplysia californica, where it elicits fast excitatory responses via dedicated cholinergic receptors.^[20] This divergence underscores evolutionary adaptations in synaptic chemistry across phyla.^[21]

Ion Channels and Depolarization

The excitatory postsynaptic potential (EPSP) arises primarily from the activation of ligand-gated ion channels in the postsynaptic membrane, which open in response to neurotransmitter binding and permit the influx of cations. These channels, predominantly AMPA receptors in glutamatergic synapses, are non-selective for monovalent cations like sodium (Na⁺) and potassium (K⁺), but the net current is depolarizing due to the predominance of Na⁺ entry.^[22] This influx reduces the membrane potential from its typical resting value of around -70 mV toward the threshold for action potential initiation, around -50 mV.^[23] The driving force for this depolarization stems from the electrochemical gradient of Na⁺, where extracellular concentrations are high (approximately 145 mM) compared to intracellular levels (about 12 mM), favoring rapid Na⁺ entry through the open channels. Although K⁺ efflux occurs simultaneously due to its gradient, the reversal potential of these channels (near 0 mV) ensures that the overall effect is a net positive charge movement into the cell, shifting the membrane potential positively.^[24] This process is highly efficient, with single-channel conductance for AMPA receptors ranging from 5 to 25 pS, enabling quick and substantial local depolarization.^[25] The time course of an AMPA receptor-mediated EPSP is characterized by a rapid rise time of approximately 1-2 ms (10%-90% amplitude), reflecting the fast kinetics of channel opening and cation permeation following glutamate release. The decay phase, lasting 10-20 ms, results from channel desensitization and deactivation, as well as the membrane time constant influenced by leak conductances and capacitance.^[26] Neurotransmitter diffusion away from the synaptic cleft also contributes to termination, preventing prolonged activation. Spatially, EPSPs generated at distal dendritic synapses attenuate in amplitude as they propagate toward the soma due to the passive cable properties of neuronal dendrites, including axial resistance and membrane capacitance. This attenuation follows exponential decay governed by the length constant (λ ≈ 0.1-0.5 mm in dendrites), with faster EPSPs experiencing greater filtering than slower ones because of the frequency-dependent nature of cable filtering.^[27] As a result, the somatic EPSP amplitude can be reduced by 50% or more for synapses located several hundred micrometers from the soma, emphasizing the role of dendritic morphology in signal integration.^[28]

Properties

Graded Nature and Summation

Excitatory postsynaptic potentials (EPSPs) are graded potentials, meaning their amplitude varies continuously depending on the strength of the synaptic input and the number of activated synapses, rather than exhibiting an all-or-nothing response like action potentials.^[4] This graded nature allows EPSPs to reflect the intensity of presynaptic activity, with typical amplitudes ranging from 0.1 to 5 mV in central neurons, often averaging around 1-2 mV for single synaptic events.^[29]^[30] Temporal summation occurs when multiple EPSPs from the same presynaptic neuron overlap in time due to high-frequency stimulation, leading to a cumulative depolarization that can build toward the action potential threshold.^[4] For instance, if successive EPSPs arrive before the previous one decays, their membrane potential changes add together, increasing the overall excitatory effect on the postsynaptic neuron.^[31] Spatial summation involves the integration of EPSPs arriving simultaneously from different presynaptic inputs at various synaptic sites on the same postsynaptic neuron, allowing the neuron to sum excitatory signals across its dendritic tree.^[4] This process enables the neuron to assess the collective input from multiple sources, potentially reaching the threshold for firing if the combined depolarization is sufficient.^[32] The amplitude of an EPSP is influenced by several factors, including the width of the synaptic cleft, which affects neurotransmitter diffusion and peak concentration at postsynaptic receptors, thereby modulating the magnitude of the response. Postsynaptic receptor density also plays a key role, as higher densities lead to greater ion influx and larger depolarizations, with EPSP size being highly sensitive to changes in this parameter.^[33] Additionally, the reversal potential for the underlying cation channels, typically around 0 mV, determines the electrochemical driving force for ion flow, further shaping EPSP amplitude based on the postsynaptic membrane potential.^[34]

Miniature EPSPs and Quantal Analysis

Miniature excitatory postsynaptic potentials (mEPSPs) are spontaneous, low-amplitude depolarizations observed in quiescent postsynaptic neurons, resulting from the release of a single vesicle of neurotransmitter at excitatory synapses. These events typically measure around 0.1-0.3 mV in amplitude at the soma in cortical and hippocampal neurons and occur independently of action potentials in the presynaptic neuron, reflecting baseline vesicular release mechanisms.^[35] In central nervous system neurons, mEPSPs provide a direct measure of quantal synaptic events, with their irregular timing and uniform shape distinguishing them from evoked responses.^[36] The quantal theory of synaptic transmission, foundational to understanding mEPSPs, posits that neurotransmitter is released in discrete packets or quanta, each corresponding to the content of a single synaptic vesicle. Developed by Bernard Katz and colleagues in the 1950s through studies on the frog neuromuscular junction, this theory demonstrated that the overall postsynaptic response arises from the synchronous release of multiple such quanta. The evoked synaptic potential is mathematically described as the product n \times p \times q, where n represents the number of available release sites, p is the probability of release at each site, and q is the quantal size (the postsynaptic response to one quantum, akin to the mEPSP amplitude). This framework, initially established at the neuromuscular junction, has been extended to central excitatory synapses, where mEPSPs serve as empirical estimates of q.^[36] Quantal analysis employs recordings of mEPSPs to quantify synaptic parameters through statistical methods, primarily by constructing frequency and amplitude histograms. Amplitude histograms reveal the distribution of mEPSP sizes, allowing estimation of q from peak separations or mean values, while frequency histograms assess release rates and variability to infer p and n. These techniques often use binomial or Poisson models to fit data, enabling precise decomposition of synaptic variability.^[37] Such analyses are particularly robust when thousands of events are recorded under controlled conditions, minimizing noise and ensuring reliable parameter extraction.^[37] In synaptic plasticity studies, quantal analysis of mEPSPs is instrumental for discerning whether changes in synaptic strength arise presynaptically (alterations in n or p) or postsynaptically (changes in q). For instance, long-term potentiation or depression can be parsed by tracking shifts in these parameters, revealing mechanisms like vesicle pool modifications or receptor trafficking. This approach has illuminated presynaptic contributions to plasticity in hippocampal and cortical circuits, providing quantitative insights into adaptive neural processes.^[38]^[39]

Measurement Techniques

Intracellular Recordings

Intracellular recordings of excitatory postsynaptic potentials (EPSPs) involve the insertion of a fine glass microelectrode into the postsynaptic neuron to directly measure changes in membrane potential triggered by presynaptic stimulation. This technique, pioneered in the mid-20th century and refined with patch-clamp methods, allows for the precise detection of depolarizing voltage shifts resulting from synaptic activation.^[40] In typical protocols, sharp microelectrodes (resistance 75–180 MΩ) filled with potassium-based solutions, such as KCH₃COOH or K-gluconate, are advanced into the soma or dendrite of the target neuron in acute brain slice preparations, often 250–400 μm thick. The recording is conducted in current-clamp mode to monitor membrane potential fluctuations near resting levels (e.g., -70 to -90 mV), with presynaptic fibers stimulated via nearby bipolar electrodes to evoke EPSPs. For instance, in hippocampal slices, stimulation of the perforant path elicits EPSPs in dentate hilar cells or CA1 pyramidal neurons, enabling the study of synaptic responses in a semi-intact neural circuit. Whole-cell patch-clamp variants achieve a high-resistance seal (>1 GΩ) before rupturing the membrane, using internal solutions like 120 mM K-gluconate and 20 mM KCl to maintain intracellular milieu during recording.^[41]^[42]^[43] This approach offers superior resolution for isolating single-synapse or unitary EPSPs, facilitating detailed analysis of their temporal kinetics, such as rise times and decay phases, which reveal voltage-dependent amplitude variations. It also supports pharmacological investigations by allowing the bath application of receptor antagonists, like CNQX for AMPA/kainate receptors or APV for NMDA receptors, to dissect underlying mechanisms without disrupting circuit-level activity.^[41]^[43] However, intracellular recordings are inherently invasive, risking mechanical damage to the neuron from electrode penetration, which can cause depolarization or instability during extended sessions. The method is largely confined to in vitro brain slices or anesthetized animals due to technical challenges in freely behaving subjects, and whole-cell configurations may lead to dialysis of intracellular components, altering natural signaling. Additionally, inadequate space-clamp in extended dendrites can distort measurements of distal EPSPs.^[42]^[41]^[43]

Field EPSPs

Field excitatory postsynaptic potentials (fEPSPs) represent extracellularly recorded signals that capture the synchronized depolarization of dendritic populations in neural ensembles, manifesting as a negative potential shift due to the influx of positive ions during excitatory synaptic transmission.^[44] This population-level response contrasts with single-cell measurements by aggregating activity from multiple neurons, providing insight into network dynamics without penetrating individual cells.^[45] In typical recording setups, extracellular microelectrodes are positioned in the stratum radiatum of the hippocampal CA1 region, where they detect fEPSPs evoked by electrical stimulation of the Schaffer collaterals from CA3 pyramidal cells. These electrodes, often glass micropipettes filled with artificial cerebrospinal fluid or multi-electrode arrays, are used in either acute brain slices or in vivo preparations to stimulate and record synaptic responses with high temporal resolution.^[46] The negative extracellular potential arises from the coordinated inward currents across many synapses, reflecting the underlying depolarization driven by ionotropic glutamate receptors.^[47] Analysis of fEPSPs focuses on the initial slope or peak amplitude of the waveform to quantify synaptic efficacy, as these metrics are less contaminated by fiber volley contributions or population spikes compared to amplitude alone.^[44] Slope measurement, in particular, is preferred for assessing changes in synaptic strength, such as those observed during long-term potentiation (LTP) induction protocols involving high-frequency stimulation. This approach has been instrumental in seminal studies demonstrating LTP as a persistent enhancement of synaptic transmission in the hippocampus.^[48] The primary advantages of fEPSP recordings include their relative non-invasiveness, enabling chronic in vivo studies in freely behaving animals to monitor network-level synaptic plasticity over extended periods. Additionally, they provide a reliable proxy for excitatory drive in distributed neural populations, facilitating the investigation of circuit-level mechanisms without the complexities of single-neuron targeting.^[45]

Comparisons and Integration

Differences from IPSPs

Excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) represent opposing forms of synaptic transmission that modulate neuronal excitability. EPSPs depolarize the postsynaptic membrane by promoting the influx of cations, primarily sodium (Na⁺), through ligand-gated ion channels, thereby increasing the likelihood of action potential generation.^[1] In contrast, IPSPs hyperpolarize the membrane or stabilize it near the resting potential through the influx of chloride ions (Cl⁻) or efflux of potassium ions (K⁺), mediated by ionotropic receptors such as GABA_A or glycine receptors, which reduces the probability of firing.^[1]^[49] A key distinction lies in their reversal potentials, which determine the direction and magnitude of the potential change relative to the membrane voltage. The reversal potential for EPSPs is typically around 0 mV, reflecting the equilibrium for nonselective cation channels permeable to Na⁺ and K⁺, making them excitatory when the membrane is at resting levels (around -70 mV).^[1] For IPSPs, the reversal potential is more negative, often near -70 mV for GABA_A-mediated Cl⁻ conductances or -80 mV for certain K⁺-selective channels, ensuring hyperpolarization or shunting inhibition from typical resting potentials.^[1] This difference in reversal potentials allows the net synaptic effect to depend on the prevailing membrane potential, with EPSPs driving toward excitation and IPSPs toward inhibition.^[1] The primary neurotransmitters underlying these potentials also differ markedly. EPSPs are predominantly elicited by glutamate binding to ionotropic receptors like AMPA and NMDA, which open cation channels.^[1] IPSPs, however, arise from inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) in the central nervous system or glycine in the spinal cord, activating Cl⁻-permeable channels.^[49]^[50] In terms of spatial organization, EPSPs typically occur at synapses distributed along the dendrites of pyramidal neurons, often on dendritic spines, facilitating widespread excitatory integration.^[51] IPSPs, by comparison, are frequently located on the soma or proximal dendrites, enabling perisomatic shunting inhibition that effectively controls action potential initiation at the axon hillock.^[52]

Neuronal Integration

Neuronal integration of excitatory postsynaptic potentials (EPSPs) with inhibitory postsynaptic potentials (IPSPs) plays a central role in decision-making processes, where the balance of these inputs determines whether a neuron reaches the threshold for action potential generation. At the soma, coincidence detection occurs as EPSPs drive depolarization while IPSPs provide counterbalancing hyperpolarization, enabling precise spike timing. This interaction operates through subtractive inhibition, where IPSPs linearly reduce the amplitude of EPSPs, and divisive inhibition, which multiplicatively scales the excitatory response via shunting conductances, thereby narrowing the temporal window for effective summation and enhancing temporal precision in hippocampal CA1 neurons.^[53]^[54] Such mechanisms ensure that only synchronously arriving excitatory inputs, unopposed or minimally opposed by inhibition, propagate to elicit spikes, as demonstrated in neocortical networks where gain modulation refines response selectivity.^[55] In dendritic compartments, local interactions between EPSPs and IPSPs facilitate nonlinear integration, allowing neurons to perform complex computations beyond simple linear summation. Shunting inhibition from GABA_A receptors introduces a multiplicative term in the somatic voltage response, approximated as somatic response ≈ EPSP + IPSP + k × EPSP × IPSP, where k quantifies shunting strength and depends on the spatial separation of excitatory and inhibitory synapses. This nonlinearity is compartment-specific: when IPSPs target dendritic branches, they confine shunting effects locally, enabling independent processing in distal regions while proximal inputs remain less affected, as observed in rat hippocampal CA1 pyramidal neurons. Active dendritic conductances further amplify these effects, with sublinear summation from IPSPs favoring distributed inputs for coincidence detection and supralinear boosts from clustered EPSPs enhancing feature selectivity.^[56]^[57] IPSPs modulate the effective spiking threshold by hyperpolarizing the membrane, thereby increasing the excitatory drive required for depolarization to reach firing levels, a dynamic essential for rhythm generation in neural networks. In septohippocampal circuits, rhythmic IPSPs synchronized to theta oscillations (1–5 Hz) trigger rebound spiking in GABAergic neurons via the hyperpolarization-activated current I_h, elevating firing rates and sustaining oscillatory patterns. This threshold adjustment prevents premature firing during inhibitory phases, promoting phase-locked activity critical for network-level rhythms like those in respiratory control or hippocampal theta generation.^[58]^[59] A prominent example is found in cortical pyramidal neurons, where perisomatic inhibition from parvalbumin-positive basket cells gates distal EPSPs by raising the somatic spiking threshold through subtractive effects and reducing gain via divisive shunting on proximal dendrites. This mechanism buffers responses to varying excitatory inputs (10–100 synapses), allowing distal dendritic computations to summate over broader timescales while enforcing precise coincidence detection at the soma, as modeled in CA1 pyramidal cells. Such gating enhances dynamic range and input selectivity in sensory processing.^[60]

Modeling and Applications

Mathematical Models

Mathematical models of excitatory postsynaptic potentials (EPSPs) provide quantitative frameworks for predicting their amplitude, time course, and propagation in neurons. A foundational approach uses a simple point-neuron approximation to estimate EPSP amplitude, where the change in membrane potential ΔV is roughly proportional to the synaptic charge transfer. Specifically, ΔV ≈ (g_syn τ_syn / C_m) (E_rev - V_m), with g_syn denoting the peak synaptic conductance, τ_syn the synaptic decay time constant (typically 2-5 ms for AMPA receptors), C_m the membrane capacitance (around 1 μF/cm²), E_rev the reversal potential (near 0 mV), and V_m the resting membrane potential (about -70 mV). This approximation assumes a brief synaptic conductance transient and neglects spatial effects, capturing the driving force (E_rev - V_m) that amplifies depolarization. Extending this to quantal release, the model incorporates probabilistic neurotransmitter vesicle exocytosis as derived from Katz's theory at the neuromuscular junction, later applied to central synapses. The evoked EPSP amplitude is modeled as E_EPSP ≈ n p q, where n is the number of release sites (or available vesicles), p the release probability (0 < p ≤ 1), and q the quantal size representing the mean unitary postsynaptic potential from one vesicle (typically 0.1-1 mV at central synapses), which incorporates the driving force (E_rev - V_m) under recording conditions. This formulation arises from observing that end-plate potentials (EPPs) fluctuate around multiples of miniature EPP amplitudes, with mean quantal content m = n p following a Poisson distribution for low p; in central neurons, binomial statistics often apply due to higher p values. For spatially extended neurons, compartmental modeling simulates EPSP propagation using discretized cable theory, commonly implemented in software like NEURON. The core equation governing voltage dynamics in each compartment is C_m dV/dt = [I_axial_in - I_axial_out] - g_leak (V - E_leak) + I_syn, where I_axial terms account for current flow between compartments via axial resistance, g_leak is leak conductance, E_leak the leak reversal potential, and I_syn = g_syn(t) (V - E_rev) the synaptic current. This framework reveals attenuation and broadening of EPSPs along dendrites, with simulations showing distal EPSPs reduced by 50-90% at the soma depending on dendritic length and diameter. Advanced models incorporate kinetic schemes for receptor gating to capture AMPA and NMDA receptor dynamics underlying EPSPs. For AMPA receptors, a simple three-state Markov scheme (closed ↔ bound-closed ↔ open) yields rapid activation and desensitization, with rate constants fitted to produce decay times of 2-5 ms; the open fraction r determines g_syn(t) = ḡ_max r, where ḡ_max is maximal conductance. NMDA receptors use a four-state scheme (closed ↔ bound ↔ open ↔ desensitized) with voltage-dependent Mg²⁺ block, resulting in slower kinetics (decay ~50-200 ms) and amplification of summed EPSPs. These schemes, derived from voltage-clamp data, enable realistic simulation of EPSP shapes and nonlinear integration. Recent studies (as of 2025) have highlighted accelerated EPSP propagation in human neocortical dendrites due to large somatic conductance loads and biophysically grounded mean-field models for simulating large-scale brain activity integrating membrane conductances and synaptic receptors.^[61]^[62]

Clinical Relevance

In epilepsy, dysregulation of excitatory postsynaptic potentials (EPSPs) arises from glutamatergic hyperactivity, where excessive glutamate release leads to hyperexcitability and seizure generation through overactivation of AMPA and NMDA receptors.^[63] This imbalance contributes to aberrant neuronal firing, as evidenced by elevated extracellular glutamate levels during seizures that disrupt normal synaptic signaling.^[64] Therapeutic strategies targeting this pathway include AMPA receptor antagonists, such as perampanel, which reduce EPSP amplitude and seizure frequency by blocking fast glutamatergic transmission without broadly impairing cognition.^[65] Emerging positive allosteric modulators of AMPA receptors are under investigation to enhance EPSP-mediated transmission for treating cognitive deficits and depression (as of 2025).^[66] Synaptic disorders like Alzheimer's disease feature reduced EPSPs due to amyloid-beta (Aβ) oligomers, which impair long-term potentiation (LTP)—a process reliant on EPSP summation—by suppressing postsynaptic signaling cascades and reducing synaptic efficacy.^[67] In autism spectrum disorder (ASD), an excitatory-inhibitory imbalance often manifests as heightened EPSP-driven activity relative to inhibitory inputs, altering circuit dynamics and contributing to sensory processing deficits.^[68] Genetic models of ASD, such as those involving fragile X syndrome, demonstrate this through enhanced excitatory synapse density and weakened inhibitory control, underscoring EPSPs' role in neurodevelopmental imbalances.^[69] Recent research in the 2020s has leveraged optogenetics to manipulate EPSPs for decoding neural circuits, enabling precise activation of glutamatergic synapses to map connectivity and dysfunction in vivo, as seen in studies combining optogenetic stimulation with patch-clamp recordings to quantify synaptic strength.^[70] In depression, ketamine enhances AMPA-mediated EPSPs by promoting AMPA receptor trafficking and synaptic potentiation, rapidly restoring prefrontal circuit activity and alleviating symptoms through metaplastic effects on glutamatergic transmission.^[71] This mechanism highlights EPSPs' involvement in mood disorders, where ketamine's blockade of NMDA receptors indirectly boosts excitatory drive.^[72] Therapeutically, drugs targeting NMDA receptors, such as memantine—an uncompetitive antagonist—modulate EPSP-dependent plasticity by preventing excitotoxicity while preserving physiological LTP, offering benefits in Alzheimer's by mitigating Aβ-induced synaptic loss.^[73] Chronic memantine pretreatment has been shown to restore hippocampal LTP and EPSP responses impaired by amyloid pathology, supporting its role in stabilizing excitatory signaling without disrupting normal cognition.^[74] These interventions underscore the potential of EPSP modulation as a target for neuroprotection across neurodegenerative and psychiatric conditions.^[75]

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EPSP amplitudes were most sensitive to changes in synaptic density and were much less sensitive to alterations in neuron input resistance and specific membrane ...
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A model of cooperative effect of AMPA and NMDA receptors in ...
Glutamatergic synapses play a pivotal role in brain excitation. The synaptic response is mediated by the activity of two receptor types (AMPA and NMDA).
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Miniature excitatory postsynaptic potentials in embryonic ... - PubMed
The mEPSPs were heterogeneous in size even within pools of potentials that were homogeneous in shape. They had similar shapes and amplitudes as the smallest ...
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Quantal Transmission at Neuromuscular Synapses - NCBI - NIH
Most of the pioneering work on neuromuscular transmission was performed by Bernard Katz and his collaborators at University College London during the 1950s and ...
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MAKING QUANTAL ANALYSIS MORE CONVENIENT, FAST, AND ...
Spontaneous release events can be detected as miniature excitatory postsynaptic potentials (mEPSP) or currents (mEPSC) using amplitude thresholds for the ...
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Presynaptic long-term plasticity - PMC - PubMed Central
The idea of using quantal analysis to identify presynaptic mechanisms was proposed by Sir Bernard Katz (1971), following the discoveries of spontaneously ...
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Quantal Analysis Reveals a Functional Correlation between ...
Jan 27, 2010 · The overall strength of synaptic connections between neurons is determined by multiple factors, some being structural (Walmsley et al., 1998; ...
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The beginning of intracellular recording in spinal neurons
Intracellular (IC) recording of action potentials in neurons of the vertebrate central nervous system (CNS) was first reported by John Eccles and two ...
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Characteristics of Spontaneous and Evoked EPSPs Recorded From ...
Excitation of the spiny subtype of hilar neurons in the fascia dentata was characterized by intracellular recording from hilar cells in hippocampal slices.
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Whole-cell Patch-clamp Recordings in Brain Slices - PMC
Jun 15, 2016 · In most cases, synaptic excitability is assessed using the whole-cell voltage-clamp technique. This recording mode allows the measurement of ion ...
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Whole-cell patch clamp electrophysiology to study ionotropic ...
Here we will discuss commonly used protocols and techniques for performing whole-cell patch clamp recordings and exploring AMPA and NMDA receptor mediated ...<|control11|><|separator|>
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Amino Acid Neurotransmitters (Section 1, Chapter 13) Neuroscience ...
Inhibitory neurotransmission (IPSPs) is mediated primarily by glycine in the spinal cord, and a metabolite of glutamate called gamma-aminobutyric acid (GABA) ...
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GABA and glycine as neurotransmitters: a brief history - PMC
We now know that at least 40% of inhibitory synaptic processing in the mammalian brain uses GABA. Establishing its role as a transmitter was a lengthy process ...
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Functional implications of inhibitory synapse placement on signal ...
Excitatory synapses onto pyramidal cells are located on dendritic spines that are widely spread across a complex dendritic arbor [1]. Dendritic inhibition can ...
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Proximity of excitatory and inhibitory axon terminals adjacent to ...
Jun 16, 2009 · The PSD of the inhibitory synapse (red) is located in the pyramidal cell body, in front of the axo-somatic terminal. The PSD of the excitatory ...
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Precise excitation-inhibition balance controls gain and timing ... - NIH
This novel gain control operation, termed Subthreshold Divisive Normalization (SDN) encodes input information in both amplitude and timing of the CA1 response.
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Neuronal arithmetic - PMC - PubMed Central - NIH
Subtractive and divisive inhibition: effect of voltage-dependent inhibitory conductances and noise. ... Sub-millisecond coincidence detection in active ...
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Rapid Neocortical Dynamics: Cellular and Network Mechanisms
Gain modulation of neuronal responses by subtractive and divisive mechanisms of inhibition. ... Adaptive coincidence detection and dynamic gain control in ...
[56]
An arithmetic rule for spatial summation of excitatory and inhibitory ...
Dendritic integration of excitatory and inhibitory inputs is critical for neuronal computation, but the underlying rules remain to be elucidated.
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Contribution of sublinear and supralinear dendritic integration to ...
Nonlinear dendritic integration is thought to increase the computational ability of neurons. Most studies focus on how supralinear summation of excitatory ...
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The Hippocamposeptal Pathway Generates Rhythmic Firing of ...
We demonstrated that carbachol-induced rhythmic theta-like hippocampal oscillations recorded extracellularly were synchronized with powerful rhythmic IPSPs in ...
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Respiratory Rhythm Generation In Vivo - PMC - PubMed Central - NIH
Here, we try to integrate the key discoveries into an updated description of the basic neural processes generating respiratory rhythm under in vivo conditions.
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Distinct and synergistic feedforward inhibition of pyramidal cells by ...
Oct 22, 2015 · FFI also allows CA1PC dendrites to sum incoming activity over broader time windows while enforcing precise coincidence detection in the soma ( ...
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Glutamatergic Mechanisms Associated with Seizures and Epilepsy
Seizures elevate extracellular glutamate—the main excitatory neurotransmitter of the brain—which leads to aberrant neuronal signaling and connectivity.
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The Role of Glutamate Receptors in Epilepsy - PMC - PubMed Central
The dysregulation of glutamate receptors and the glutamatergic system is involved in numerous neurological and psychiatric disorders, especially epilepsy.
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Ionotropic Glutamate Receptors in Epilepsy: A Review Focusing on ...
It is known that AMPA receptor activity mediates fast synaptic transmission and has an important role in the early phase of excitatory synaptic potential, ...2.1. Ampa Receptors · 2.2. Nmda Receptor · 5. Role Of Nmda And Ampa...
[64]
Soluble Aβ Oligomers Inhibit Long-Term Potentiation through a ...
Numerous studies report that hippocampal long-term potentiation (LTP) can be inhibited by soluble oligomers of amyloid β-protein (Aβ), but the synaptic elements ...
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Increased excitation-inhibition ratio stabilizes synapse and circuit ...
A simple synaptic conductance model explains why increased E-I conductance ratio does not generate stronger PSPs or more spiking in ASD mutants: In all 4 ASD ...
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Genetic Controls Balancing Excitatory and Inhibitory ...
Genetic models of FXS exhibit striking excitatory and inhibitory synapse imbalance, associated with impaired cognitive and social interaction behaviors.
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Studying Synaptic Connectivity and Strength with Optogenetics and ...
We seek to provide practical insights into the methods used to study neural circuits and synapses, by combining optogenetics and patch-clamp electrophysiology.
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Essential roles of AMPA receptor GluA1 phosphorylation and ... - NIH
Dec 13, 2016 · Ketamine enhances synaptic transmission and GluA1 phosphorylation through a protein kinase A–dependent pathway · Ketamine increases the abundance ...
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Signaling Pathways Underlying the Rapid Antidepressant Actions of ...
Ketamine rapidly increases synaptogenesis, including increased density and function of spine synapses, in the prefrontal cortex (PFC).
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Alzheimer's disease, β-amyloid, glutamate, NMDA receptors and ...
As NMDA receptors are critically involved in neuronal plasticity including learning and memory, we felt that it would be valuable to provide an up to date ...
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Chronic pre-treatment with memantine prevents amyloid-beta ... - NIH
In addition, memantine increases the durability of synaptic plasticity in moderately aged rats and prevents the impaired LTP resulting from exogenous NMDA or ...
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Pharmacodynamics of Memantine: An Update - PMC
Memantine is a moderate affinity, uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist with strong voltage-dependency and fast kinetics.