scholarly journals Increased and synchronous recruitment of release sites underlies hippocampal mossy fiber presynaptic potentiation

2020 ◽  
Author(s):  
Marta Orlando ◽  
Anton Dvorzhak ◽  
Felicitas Bruentgens ◽  
Marta Maglione ◽  
Benjamin R. Rost ◽  
...  
Keyword(s):  
Mossy Fiber ◽  
Glutamate Release ◽  
Long Term Potentiation ◽  
Stimulated Emission ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Term Potentiation ◽  
Synaptic Ultrastructure ◽  
Electron Microscopy Analysis

ABSTRACTSynaptic plasticity is a cellular model for learning and memory. However, the expression mechanisms underlying presynaptic forms of plasticity are not well understood. Here, we investigate functional and structural correlates of long-term potentiation at large hippocampal mossy fiber boutons induced by the adenylyl cyclase activator forskolin. We performed two-photon imaging of the genetically encoded glutamate sensor iGluu that revealed an increase in the surface area used for glutamate release at potentiated terminals. Moreover, time-gated stimulated emission depletion microscopy revealed no change in the coupling distance between immunofluorescence signals from calcium channels and release sites. Finally, by high-pressure freezing and transmission electron microscopy analysis, we found a fast remodeling of synaptic ultrastructure at potentiated boutons: synaptic vesicles dispersed in the terminal and accumulated at the active zones, while active zone density and synaptic complexity increased. We suggest that these rapid and early structural rearrangements likely enable long-term increase in synaptic strength.

scholarly journals Recruitment of release sites underlies chemical presynaptic potentiation at hippocampal mossy fiber boutons

PLoS Biology ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. e3001149
Author(s):  
Marta Orlando ◽  
Anton Dvorzhak ◽  
Felicitas Bruentgens ◽  
Marta Maglione ◽  
Benjamin R. Rost ◽  
...  
Keyword(s):  
Mossy Fiber ◽  
Glutamate Release ◽  
Stimulated Emission ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Synaptic Ultrastructure ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis ◽  
Cyclase Activator

Synaptic plasticity is a cellular model for learning and memory. However, the expression mechanisms underlying presynaptic forms of plasticity are not well understood. Here, we investigate functional and structural correlates of presynaptic potentiation at large hippocampal mossy fiber boutons induced by the adenylyl cyclase activator forskolin. We performed 2-photon imaging of the genetically encoded glutamate sensor iGluu that revealed an increase in the surface area used for glutamate release at potentiated terminals. Time-gated stimulated emission depletion microscopy revealed no change in the coupling distance between P/Q-type calcium channels and release sites mapped by Munc13-1 cluster position. Finally, by high-pressure freezing and transmission electron microscopy analysis, we found a fast remodeling of synaptic ultrastructure at potentiated boutons: Synaptic vesicles dispersed in the terminal and accumulated at the active zones, while active zone density and synaptic complexity increased. We suggest that these rapid and early structural rearrangements might enable long-term increase in synaptic strength.

Maintenance of long-term potentiation in hippocampal mossy fiber-CA3 pathway requires fine-tuned MMP-9 proteolytic activity

Hippocampus ◽  
2013 ◽  
Vol 23 (6) ◽  
pp. 529-543 ◽  
Author(s):  
Grzegorz Wiera ◽  
Grazyna Wozniak ◽  
Malgorzata Bajor ◽  
Leszek Kaczmarek ◽  
Jerzy W. Mozrzymas
Keyword(s):  
Proteolytic Activity ◽  
Mossy Fiber ◽  
Long Term Potentiation ◽  
Term Potentiation

scholarly journals Metabotropic Glutamate Receptor Antagonist AIDA Blocks Induction of Mossy Fiber-CA3 LTP In Vivo

2005 ◽  
Vol 93 (5) ◽  
pp. 2668-2673 ◽  
Author(s):  
Kenira J. Thompson ◽  
Mario L. Mata ◽  
James E. Orfila ◽  
Edwin J. Barea-Rodriguez ◽  
Joe L. Martinez
Keyword(s):  
Mossy Fiber ◽  
Long Term Potentiation ◽  
Initial Slope ◽  
Maximal Response ◽  
Excitatory Postsynaptic Potential ◽  
Sprague Dawley ◽  
Metabotropic Glutamate ◽  
Term Potentiation

Metabotropic glutamate receptors (mGluR) are implicated in long-term memory storage. mGluR-I and mGluR-II antagonists impede various forms of learning and long-term potentiation (LTP) in animals. Despite the evidence linking mGluR to learning mechanisms, their role in mossy fiber-CA3 long-term potentiation (LTP) is not yet clear. To explain the involvement of mGluR-I in memory mechanisms, we examined the function of the mGluR-I antagonist 1-aminoindan-1, 5-dicarboxylic acid (AIDA) on the induction of mossy fiber-CA3 LTP in vivo in male Sprague Dawley and Fischer 344 (F344) rats. Acute extracellular mossy fiber (MF) responses were evoked by stimulation of the MF bundle and recorded in the stratum lucidum of CA3. The excitatory postsynaptic potential (EPSP) magnitude was measured by using the initial slope of the field EPSP slope measured 2–3 ms after response onset. After collection of baseline MF-CA3 responses at 0.05 Hz, animals received either ((±))-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid ( N-methyl-d-aspartate-R antagonist, 10 mg/kg ip), naloxone (opioid-R antagonist, 10 mg/kg ip), or AIDA (mGluR antagonist, 1 mg/kg ip or 37.5 nmol ic). LTP was induced by two 100-Hz trains at the intensity sufficient to evoke 50% of the maximal response. Responses were collected for an additional 1 h. AIDA blocked induction of LTP in the mossy fiber pathway ( P < 0.05) in both strains of rats after systemic and in Sprague Dawley rats after intrahippocampal injection.

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