scholarly journals Long-Term Potentiation of Excitatory Synapses on Neocortical Somatostatin-Expressing Interneurons

2009 ◽  
Vol 102 (6) ◽  
pp. 3251-3259 ◽  
Author(s):  
Huan-Xin Chen ◽  
Mali Jiang ◽  
Dilek Akakin ◽  
Steven N. Roper
Keyword(s):  
Fluorescent Protein ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Long Term Potentiation ◽  
Excitatory Synapses ◽  
Term Potentiation ◽  
Voltage Dependent ◽  
Green Fluorescent ◽  
Theta Burst

Synaptic plasticity has been extensively studied in principal neurons of the neocortex, but less work has been done on GABAergic interneurons. Interneurons consist of multiple subtypes and their synaptic properties vary between subtypes. In the present study, we have examined long-term potentiation (LTP) of excitatory synapses on somatostatin (SS)-expressing interneurons in neocortex using transgenic mice that express enhanced green fluorescent protein in these interneurons. We found that a strong theta burst stimulation was required to induce LTP in SS interneurons. LTP was associated with a reduction in paired-pulse facilitation and was not blocked by an N-methyl-d-aspartate receptor (NMDAR) antagonist. LTP was not affected by chelating postsynaptic Ca2+ with BAPTA, a fast Ca2+ chelator, and blocking L-type voltage-dependent Ca2+ channels with nimodipine. Application of forskolin, an activator of adenylate cyclase that increases cyclic adenosine monophosphate (cAMP) concentration, enhanced synaptic transmission and occluded subsequent induction of LTP. Finally, we found that LTP was blocked by protein kinase A (PKA) inhibitors. Our results suggest that excitatory synapses on SS interneurons express a presynaptic form of LTP that is not dependent on NMDARs or postsynaptic Ca2+ rise but is dependent on the cAMP–PKA signaling pathway.

scholarly journals GluA1 trafficking and metabotropic NMDA: addressing results from other laboratories inconsistent with ours

2014 ◽  
Vol 369 (1633) ◽  
pp. 20130145 ◽  
Author(s):  
Sadegh Nabavi ◽  
Rocky Fox ◽  
Stephanie Alfonso ◽  
Jonathan Aow ◽  
Roberto Malinow
Keyword(s):  
Fluorescent Protein ◽  
Long Term Potentiation ◽  
Long Term Depression ◽  
Mk 801 ◽  
Over Expression ◽  
Term Potentiation ◽  
The Difference ◽  
Green Fluorescent ◽  
Gfp Tag

We have previously shown that when over-expressed in neurons, green fluorescent protein (GFP) tagged GluA1 (GluA1-GFP) delivery into synapses is dependent on plasticity. A recent study suggests that GluA1 over-expression leads to its incorporation into the synapse, in the absence of additional long-term potentiation-like manipulations. It is possible that a GFP tag was responsible for the difference. Using rectification index as a measure of synaptic delivery of GluA1, we found no difference in the synaptic delivery of GluA1-GFP versus untagged GluA1. We recently published a study showing that while D-APV blocks NMDAr-dependent long-term depression (LTD), MK-801 and 7-chloro kynurenate (7CK) fail to block LTD. We propose a metabotropic function for the NMDA receptor in LTD induction. In contrast to our observations, recent unpublished data suggest that the above antagonists are equally effective in blocking LTD. We noticed different methodology in their study. Here, we show that their methodology has complex effects on synaptic transmission. Therefore, it is not possible to conclude that 7CK is effective in blocking LTD from their type of experiment.

scholarly journals Large and Small Dendritic Spines Serve Different Interacting Functions in Hippocampal Synaptic Plasticity and Homeostasis

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Joshua J. W. Paulin ◽  
Peter Haslehurst ◽  
Alexander D. Fellows ◽  
Wenfei Liu ◽  
Joshua D. Jackson ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Fluorescent Protein ◽  
Long Term Potentiation ◽  
Functional Differentiation ◽  
Strong Stimulus ◽  
Term Potentiation ◽  
Original Size ◽  
Green Fluorescent ◽  
Homeostatic Response

The laying down of memory requires strong stimulation resulting in specific changes in synaptic strength and corresponding changes in size of dendritic spines. Strong stimuli can also be pathological, causing a homeostatic response, depressing and shrinking the synapse to prevent damage from too much Ca2+influx. But do all types of dendritic spines serve both of these apparently opposite functions? Using confocal microscopy in organotypic slices from mice expressing green fluorescent protein in hippocampal neurones, the size of individual spines along sections of dendrite has been tracked in response to application of tetraethylammonium. This strong stimulus would be expected to cause both a protective homeostatic response and long-term potentiation. We report separation of these functions, with spines of different sizes reacting differently to the same strong stimulus. The immediate shrinkage of large spines suggests a homeostatic protective response during the period of potential danger. In CA1, long-lasting growth of small spines subsequently occurs consolidating long-term potentiation but only after the large spines return to their original size. In contrast, small spines do not change in dentate gyrus where potentiation does not occur. The separation in time of these changes allows clear functional differentiation of spines of different sizes.

scholarly journals Excitatory synapses are stronger in the hippocampus of Rett syndrome mice due to altered synaptic trafficking of AMPA-type glutamate receptors

2016 ◽  
Vol 113 (11) ◽  
pp. E1575-E1584 ◽  
Author(s):  
Wei Li ◽  
Xin Xu ◽  
Lucas Pozzo-Miller
Keyword(s):  
Rett Syndrome ◽  
Pyramidal Neurons ◽  
Long Term Potentiation ◽  
Excitatory Synapses ◽  
Afferent Stimulation ◽  
Altered Expression ◽  
Hippocampal Pyramidal Neurons ◽  
Term Potentiation ◽  
Theta Burst

Deficits in long-term potentiation (LTP) at central excitatory synapses are thought to contribute to cognitive impairments in neurodevelopmental disorders associated with intellectual disability and autism. Using the methyl-CpG-binding protein 2 (Mecp2) knockout (KO) mouse model of Rett syndrome, we show that naïve excitatory synapses onto hippocampal pyramidal neurons of symptomatic mice have all of the hallmarks of potentiated synapses. Stronger Mecp2 KO synapses failed to undergo LTP after either theta-burst afferent stimulation or pairing afferent stimulation with postsynaptic depolarization. On the other hand, basal synaptic strength and LTP were not affected in slices from younger presymptomatic Mecp2 KO mice. Furthermore, spine synapses in pyramidal neurons from symptomatic Mecp2 KO are larger and do not grow in size or incorporate GluA1 subunits after electrical or chemical LTP. Our data suggest that LTP is occluded in Mecp2 KO mice by already potentiated synapses. The higher surface levels of GluA1-containing receptors are consistent with altered expression levels of proteins involved in AMPA receptor trafficking, suggesting previously unidentified targets for therapeutic intervention for Rett syndrome and other MECP2-related disorders.

scholarly journals PKA drives an increase in AMPA receptor unitary conductance during LTP in the hippocampus

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pojeong Park ◽  
John Georgiou ◽  
Thomas M. Sanderson ◽  
Kwang-Hee Ko ◽  
Heather Kang ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Single Channel ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Theta Burst Stimulation ◽  
Term Potentiation ◽  
Hippocampal Ca1 ◽  
Necessary And Sufficient ◽  
Theta Burst

AbstractLong-term potentiation (LTP) at hippocampal CA1 synapses can be expressed by an increase either in the number (N) of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors or in their single channel conductance (γ). Here, we have established how these distinct synaptic processes contribute to the expression of LTP in hippocampal slices obtained from young adult rodents. LTP induced by compressed theta burst stimulation (TBS), with a 10 s inter-episode interval, involves purely an increase in N (LTPN). In contrast, either a spaced TBS, with a 10 min inter-episode interval, or a single TBS, delivered when PKA is activated, results in LTP that is associated with a transient increase in γ (LTPγ), caused by the insertion of calcium-permeable (CP)-AMPA receptors. Activation of CaMKII is necessary and sufficient for LTPN whilst PKA is additionally required for LTPγ. Thus, two mechanistically distinct forms of LTP co-exist at these synapses.

Theta-burst stimulation of primary afferents drives long-term potentiation in the spinal cord and persistent pain via α2δ-1–bound NMDA receptors

2021 ◽  
pp. JN-RM-1968-21
Author(s):  
Yuying Huang (黄玉莹) ◽  
Shao-Rui Chen (陈少瑞) ◽  
Hong Chen (陈红) ◽  
Jing-Jing Zhou (周京京) ◽  
Daozhong Jin (金道忠) ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Nmda Receptors ◽  
Long Term Potentiation ◽  
Primary Afferents ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Term Potentiation ◽  
Theta Burst ◽  
Stimulation Of

scholarly journals Proteasome and Autophagy-Mediated Impairment of Late Long-Term Potentiation (l-LTP) after Traumatic Brain Injury in the Somatosensory Cortex of Mice

2019 ◽  
Vol 20 (12) ◽  
pp. 3048 ◽  
Author(s):  
Feldmann ◽  
Le Prieult ◽  
Felzen ◽  
Thal ◽  
Engelhard ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Protein Degradation ◽  
Long Term Potentiation ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Ipsilateral Hemisphere ◽  
Term Potentiation ◽  
Theta Burst

Traumatic brain injury (TBI) can lead to impaired cognition and memory consolidation.The acute phase (24–48 h) after TBI is often characterized by neural dysfunction in the vicinity ofthe lesion, but also in remote areas like the contralateral hemisphere. Protein homeostasis is crucialfor synaptic long-term plasticity including the protein degradation systems, proteasome andautophagy. Still, little is known about the acute effects of TBI on synaptic long-term plasticity andprotein degradation. Thus, we investigated TBI in a controlled cortical impact (CCI) model in themotor and somatosensory cortex of mice ex vivo-in vitro. Late long-term potentiation (l-LTP) wasinduced by theta-burst stimulation in acute brain slices after survival times of 1–2 days. Proteinlevels for the plasticity related protein calcium/calmodulin-dependent protein kinase II (CaMKII)was quantified by Western blots, and the protein degradation activity by enzymatical assays. Weobserved missing maintenance of l-LTP in the ipsilateral hemisphere, however not in thecontralateral hemisphere after TBI. Protein levels of CaMKII were not changed but, interestingly,the protein degradation revealed bidirectional changes with a reduced proteasome activity and anincreased autophagic flux in the ipsilateral hemisphere. Finally, LTP recordings in the presence ofpharmacologically modified protein degradation systems also led to an impaired synaptic plasticity:bath-applied MG132, a proteasome inhibitor, or rapamycin, an activator of autophagy, bothadministered during theta burst stimulation, blocked the induction of LTP. These data indicate thatalterations in protein degradation pathways likely contribute to cognitive deficits in the acute phaseafter TBI, which could be interesting for future approaches towards neuroprotective treatmentsearly after traumatic brain injury.

scholarly journals Role of Voltage-Dependent Calcium Channel Long-Term Potentiation (LTP) and NMDA LTP in Spatial Memory

2000 ◽  
Vol 20 (24) ◽  
pp. 9272-9276 ◽  
Author(s):  
Albert M. Borroni ◽  
Harlan Fichtenholtz ◽  
Brian L. Woodside ◽  
Timothy J. Teyler
Keyword(s):  
Spatial Memory ◽  
Calcium Channel ◽  
Long Term Potentiation ◽  
Voltage Dependent Calcium Channel ◽  
Term Potentiation ◽  
Voltage Dependent

scholarly journals Chemical LTD, but not LTP, induces transient accumulation of gelsolin in dendritic spines

2019 ◽  
Vol 400 (9) ◽  
pp. 1129-1139 ◽  
Author(s):  
Iryna Hlushchenko ◽  
Pirta Hotulainen
Keyword(s):  
Synaptic Plasticity ◽  
Dendritic Spines ◽  
Hippocampal Neurons ◽  
Long Term Potentiation ◽  
Excitatory Synapses ◽  
Signal Molecule ◽  
Brain Functions ◽  
Dendritic Shaft ◽  
Term Potentiation

Abstract Synaptic plasticity underlies central brain functions, such as learning. Ca2+ signaling is involved in both strengthening and weakening of synapses, but it is still unclear how one signal molecule can induce two opposite outcomes. By identifying molecules, which can distinguish between signaling leading to weakening or strengthening, we can improve our understanding of how synaptic plasticity is regulated. Here, we tested gelsolin’s response to the induction of chemical long-term potentiation (cLTP) or long-term depression (cLTD) in cultured rat hippocampal neurons. We show that gelsolin relocates from the dendritic shaft to dendritic spines upon cLTD induction while it did not show any relocalization upon cLTP induction. Dendritic spines are small actin-rich protrusions on dendrites, where LTD/LTP-responsive excitatory synapses are located. We propose that the LTD-induced modest – but relatively long-lasting – elevation of Ca2+ concentration increases the affinity of gelsolin to F-actin. As F-actin is enriched in dendritic spines, it is probable that increased affinity to F-actin induces the relocalization of gelsolin.

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