scholarly journals AMPA receptor subunit GluR1 (GluA1) serine-845 site is involved in synaptic depression but not in spine shrinkage associated with chemical long-term depression

2011 ◽  
Vol 105 (4) ◽  
pp. 1897-1907 ◽  
Author(s):  
Kaiwen He ◽  
Angela Lee ◽  
Lihua Song ◽  
Patrick O. Kanold ◽  
Hey-Kyoung Lee
Keyword(s):  
Ampa Receptor ◽  
Molecular Mechanisms ◽  
Pyramidal Neurons ◽  
Low Frequency ◽  
Morphological Plasticity ◽  
Mutant Mice ◽  
Long Term Depression ◽  
Spine Head ◽  
Nmdar Activation

The structure of dendritic spines is highly plastic and can be modified by neuronal activity. In addition, there is evidence that spine head size correlates with the synaptic α-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptor (AMPAR) content, which suggests that they may be coregulated. Although there is evidence that there are overlapping mechanisms for structural and functional plasticity, the extent of the overlap needs further investigation. Specifically, it is unknown whether AMPAR levels determine spine size or whether both are regulated via parallel pathways. We studied the correlation between spine structural plasticity and long-term synaptic plasticity following chemical-induced long-term depression (chemLTD). In particular, we examined whether the regulation of AMPARs, which is implicated in LTD, is critical for spine morphological plasticity. We used mutant mice specifically lacking the serine-845 site on the type 1 glutamate receptor (GluR1, or GluA1) subunit of AMPARs (mutants). These mice specifically lack N-methyl-d-aspartate (NMDA) receptor (NMDAR)-dependent LTD and NMDAR activation-induced AMPAR endocytosis. We found that chemLTD causes a rapid and persistent shrinkage in spine head volume of hippocampal CA1 pyramidal neurons in wild types similar to that reported in other studies using low-frequency stimulation (LFS)-induced LTD. Surprisingly, we found that although S845A mutant mice display impaired chemLTD, the shrinkage of spine head volume occurred to a similar magnitude to that observed in wild types. Our results suggest that there is dissociation in the molecular mechanisms underlying functional LTD and spine shrinkage and that GluR1-S845 regulation is not necessary for spine morphological plasticity.

Low-frequency stimulation at the troughs of theta-oscillation induces long-term depression of previously potentiated CA1 synapses

1996 ◽  
Vol 75 (2) ◽  
pp. 877-884 ◽  
Author(s):  
P. T. Huerta ◽  
J. E. Lisman
Keyword(s):  
Hippocampal Slices ◽  
Field Potential ◽  
Low Frequency ◽  
Long Term Depression ◽  
Low Frequency Stimulation ◽  
Bath Application ◽  
Stable Conditions ◽  
Theta Frequency ◽  
Frequency Stimulation

1. The induction of long-term weakening of synaptic transmission in rat hippocampal slices was examined in CA1 synapses during cholinergic modulation. 2. Bath application of the cholinergic agonist carbachol (50 microM) activated an oscillation of the local field potential in the theta-frequency range (5-12 Hz), termed theta. It was previously shown that a stimulation train of 40 single shocks (at 0.1 Hz) to the Schaffer collateral-commisural afferents, each synchronized with positive peaks of theta, caused homosynaptic long-term enhancement in CA1. Furthermore, long-term depression (LTD) was sporadically observed when the stimulation train was given at negative troughs of theta. Here we have sought to determine stable conditions for LTD induction during theta. 3. Synaptic weakening was reliably obtained, by giving 40 shocks (at 0.1 Hz) at theta-troughs, only in pathways that had been previously potentiated. This decrement, termed theta-LTD, was synapse specific because it did not occur in an independent pathway not stimulated during theta. The interval between the initial potentiating tetanus and theta-LTD induction could be as long as 90 min. 4. theta-LTD could be saturated; after consecutive episodes of theta-LTD induction, no significant further depression was obtained. Moreover, theta-LTD could be reversed by tetanic stimulation. 5. theta-LTD could prevent the induction of LTD by 600-900 pulses at 1 Hz. This suggests that the two protocols may share common mechanisms at the synaptic level. 6. We conclude that single presynaptic spikes that occur at low frequency and are properly timed to the troughs of theta may be a relevant mechanism for decreasing the strength of potentiated synapses.

scholarly journals GSK3β Modulates Timing-Dependent Long-Term Depression Through Direct Phosphorylation of Kv4.2 Channels

2018 ◽  
Vol 29 (5) ◽  
pp. 1851-1865 ◽  
Author(s):  
Giuseppe Aceto ◽  
Agnese Re ◽  
Andrea Mattera ◽  
Lucia Leone ◽  
Claudia Colussi ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Synaptic Strength ◽  
Spike Timing ◽  
Long Term Depression ◽  
Pharmacological Agents ◽  
Type K ◽  
Molecular Determinant ◽  
K Currents

AbstractSpike timing-dependent plasticity (STDP) is a form of activity-dependent remodeling of synaptic strength that underlies memory formation. Despite its key role in dictating learning rules in the brain circuits, the molecular mechanisms mediating STDP are still poorly understood. Here, we show that spike timing-dependent long-term depression (tLTD) and A-type K+ currents are modulated by pharmacological agents affecting the levels of active glycogen-synthase kinase 3 (GSK3) and by GSK3β knockdown in layer 2/3 of the mouse somatosensory cortex. Moreover, the blockade of A-type K+ currents mimics the effects of GSK3 up-regulation on tLTD and occludes further changes in synaptic strength. Pharmacological, immunohistochemical and biochemical experiments revealed that GSK3β influence over tLTD induction is mediated by direct phosphorylation at Ser-616 of the Kv4.2 subunit, a molecular determinant of A-type K+ currents. Collectively, these results identify the functional interaction between GSK3β and Kv4.2 channel as a novel mechanism for tLTD modulation providing exciting insight into the understanding of GSK3β role in synaptic plasticity.

Long-Term Depression of Temporoammonic-CA1 Hippocampal Synaptic Transmission

1999 ◽  
Vol 81 (3) ◽  
pp. 1036-1044 ◽  
Author(s):  
Hannah Dvorak-Carbone ◽  
Erin M. Schuman
Keyword(s):  
Synaptic Transmission ◽  
Calcium Influx ◽  
Hippocampal Slices ◽  
Low Frequency ◽  
Nmda Receptor Antagonist ◽  
Long Term Depression ◽  
Field Recordings ◽  
Old Rats ◽  
Inhibitory Components

Long-term depression of temporoammonic-CA1 hippocampal synaptic transmission. The temporoammonic pathway, the direct projection from layer III of the entorhinal cortex to area CA1 of the hippocampus, includes both excitatory and inhibitory components that are positioned to be an important source of modulation of the hippocampal output. However, little is known about synaptic plasticity in this pathway. We used field recordings in hippocampal slices prepared from mature (6- to 8-wk old) rats to study long-term depression (LTD) in the temporoammonic pathway. Low-frequency (1 Hz) stimulation (LFS) for 10 min resulted in a depression of the field response that lasted for ≥1 h. This depression was saturable by multiple applications of LFS. LTD induction was unaffected by the blockade of either fast (GABAA) or slow (GABAB) inhibition. Temporoammonic LTD was inhibited by the presence of the N-methyl-d-aspartate (NMDA) receptor antagonist AP5, suggesting a dependence on calcium influx. Full recovery from depression could be induced by high-frequency (100 Hz) stimulation (HFS); in the presence of the GABAA antagonist bicuculline, HFS induced recovery above the original baseline level. Similarly, HFS or θ-burst stimulation (TBS) applied to naive slices caused little potentiation, whereas HFS or TBS applied in the presence of bicuculline resulted in significant potentiation of the temporoammonic response. Our results show that, unlike the Schaffer collateral input to CA1, the temporoammonic input in mature animals is easy to depress but difficult to potentiate.

Stimulation at 1-5 Hz does not produce long-term depression or depotentiation in the hippocampus of the adult rat in vivo

1995 ◽  
Vol 74 (4) ◽  
pp. 1793-1799 ◽  
Author(s):  
M. L. Errington ◽  
T. V. Bliss ◽  
G. Richter-Levin ◽  
K. Yenk ◽  
V. Doyere ◽  
...  
Keyword(s):  
Young Animal ◽  
Low Frequency ◽  
Long Term Depression ◽  
Developmentally Regulated ◽  
Adult Rats ◽  
Adult Rat ◽  
Area Ca1 ◽  
Awake Rat

1. We examined the efficacy of low-frequency trains (1-5 Hz) in producing long-term depression (LTD) or depotentiation in the hippocampus of the awake adult rat and in anesthetized rats aged from 10 days to 3 mo. 2. In the dentate gyrus we found no evidence that low-frequency trains produce either depotentiation or LTD in the awake, adult animal or in the anesthetized animal at any age tested (10 days-adult). 3. In area CA1 of both awake and anesthetized adult rats, we also found no evidence that low-frequency trains induced either LTD or depotentiation. Only in area CA1 of very young rats (10-11 days) was clear evidence for LTD and depotentiation obtained; at this age experiments were only possible in anesthetized animals. By 16 days, the ability to display both LTD and depotentiation was lost. 4. These experiments suggest that repetitive low-frequency stimulation evokes a developmentally regulated form of activity-dependent depression that in the hippocampus is limited to specific pathways in the young animal. Our results leave open the question of whether alternative patterns of activity can induce LTD and/or depotentiation in the adult awake rat.

scholarly journals Long-term depression: a cell biological view

2014 ◽  
Vol 369 (1633) ◽  
pp. 20130138 ◽  
Author(s):  
Morgan Sheng ◽  
Ali Ertürk
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Dendritic Spines ◽  
Crucial Role ◽  
Molecular Mechanisms ◽  
Signalling Pathways ◽  
Long Term Depression ◽  
A Cell ◽  
Biological Programme

Recent studies of the molecular mechanisms of long-term depression (LTD) suggest a crucial role for the signalling pathways of apoptosis (programmed cell death) in the weakening and elimination of synapses and dendritic spines. With this backdrop, we suggest that LTD can be considered as the electrophysiological aspect of a larger cell biological programme of synapse involution, which uses localized apoptotic mechanisms to sculpt synapses and circuits without causing cell death.

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