Effects of aging on axon terminals in the dentate molecular layer

1987 ◽  
Vol 45 ◽  
pp. 928-929
Author(s):  
K. Cullen-Dockstader ◽  
E. Fifkova
Keyword(s):  
Granule Cells ◽  
Molecular Layer ◽  
Age Groups ◽  
Long Term Potentiation ◽  
Male Rats ◽  
Perforant Path ◽  
Axon Terminals ◽  
Fischer 344 ◽  
Spatial Memory Deficit ◽  
Effects Of Aging

Normal aging results in a pronounced spatial memory deficit associated with a rapid decay of long-term potentiation at the synapses between the perforant path and spines in the medial and distal thirds of the dentate molecular layer (DML), suggesting the alteration of synaptic transmission in the dentate fascia. While the number of dentate granule cells remains unchanged, and there are no obvious pathological changes in these cells associated with increasing age, the density of their axospinous contacts has been shown to decrease. There are indications that the presynaptic element is affected by senescence before the postsynaptic element, yet little attention has been given to the fine structure of the remaining axon terminals. Therefore, we studied the axon terminals of the perforant path in the DML across three age groups.5 Male rats (Fischer 344) of each age group (3, 24 and 30 months), were perfused through the aorta.

scholarly journals Structural homo- and heterosynaptic plasticity in mature and adult newborn rat hippocampal granule cells

2018 ◽  
Vol 115 (20) ◽  
pp. E4670-E4679 ◽  
Author(s):  
Tassilo Jungenitz ◽  
Marcel Beining ◽  
Tijana Radic ◽  
Thomas Deller ◽  
Hermann Cuntz ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Granule Cells ◽  
Molecular Layer ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
High Frequency Stimulation ◽  
Spatial Learning And Memory ◽  
Heterosynaptic Plasticity ◽  
Spine Plasticity

Adult newborn hippocampal granule cells (abGCs) contribute to spatial learning and memory. abGCs are thought to play a specific role in pattern separation, distinct from developmentally born mature GCs (mGCs). Here we examine at which exact cell age abGCs are synaptically integrated into the adult network and which forms of synaptic plasticity are expressed in abGCs and mGCs. We used virus-mediated labeling of abGCs and mGCs to analyze changes in spine morphology as an indicator of plasticity in rats in vivo. High-frequency stimulation of the medial perforant path induced long-term potentiation in the middle molecular layer (MML) and long-term depression in the nonstimulated outer molecular layer (OML). This stimulation protocol elicited NMDA receptor-dependent homosynaptic spine enlargement in the MML and heterosynaptic spine shrinkage in the inner molecular layer and OML. Both processes were concurrently present on individual dendritic trees of abGCs and mGCs. Spine shrinkage counteracted spine enlargement and thus could play a homeostatic role, normalizing synaptic weights. Structural homosynaptic spine plasticity had a clear onset, appearing in abGCs by 28 d postinjection (dpi), followed by heterosynaptic spine plasticity at 35 dpi, and at 77 dpi was equally as present in mature abGCs as in mGCs. From 35 dpi on, about 60% of abGCs and mGCs showed significant homo- and heterosynaptic plasticity on the single-cell level. This demonstration of structural homo- and heterosynaptic plasticity in abGCs and mGCs defines the time course of the appearance of synaptic plasticity and integration for abGCs.

scholarly journals Somatostatin Depresses Long-Term Potentiation and Ca2+ Signaling in Mouse Dentate Gyrus

2002 ◽  
Vol 88 (6) ◽  
pp. 3078-3086 ◽  
Author(s):  
Michael V. Baratta ◽  
Tyra Lamp ◽  
Melanie K. Tallent
Keyword(s):  
Dentate Gyrus ◽  
High Frequency ◽  
Granule Cells ◽  
Molecular Layer ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
Functional Consequence ◽  
Term Potentiation ◽  
Synaptic Responses

The selective loss of somatostatin (SST)-containing interneurons from the hilus of the dentate gyrus is a hallmark of epileptic hippocampus. The functional consequence of this loss, including its contribution to postseizure hyperexcitability, remains unclear. We address this issue by characterizing the actions of SST in mouse dentate gyrus using electrophysiological techniques. Although the majority of dentate SST receptors are located in the outer molecular layer adjacent to lateral perforant path (LPP) synapses, we found no consistent action of SST on standard synaptic responses generated at these synapses. However, when SST was present during application of high-frequency trains that normally generate long-term potentiation (LTP), the induction of LTP was impaired. SST did not alter the maintenance of LTP when applied after its induction. To examine the mechanism by which SST inhibits LTP, we recorded from dentate granule cells and examined the actions of this neuropeptide on synaptic transmission and postsynaptic currents. Unlike findings in the CA1 hippocampus, we observed no postsynaptic actions on K+ currents. Instead, SST inhibited Ca2+/Ba2+ spikes evoked by depolarization. This inhibition was dependent on N-type Ca2+currents. Blocking these currents also blocked LTP, suggesting a mechanism through which SST may inhibit LTP. Our results indicate that SST reduction of dendritic Ca2+ through N-type Ca2+ channels may contribute to modulation of synaptic plasticity at LPP synapses. Therefore the loss of SST function postseizure could result in abnormal synaptic potentiation that contributes to epileptogenesis.

Hydroxylation of salicylate in lungs of Fischer 344 rats: effects of aging and ozone exposure

1996 ◽  
Vol 271 (6) ◽  
pp. L995-L1003 ◽  
Author(s):  
L. Liu ◽  
P. Kumarathasan ◽  
J. Guenette ◽  
R. Vincent
Keyword(s):  
Chemical Reduction ◽  
Age Groups ◽  
Ozone Exposure ◽  
Male Rats ◽  
Adult Rats ◽  
Fischer 344 ◽  
Clean Air ◽  
Oxidant Production ◽  
Effects Of Aging ◽  
Air Control

The formation of 2,3-dihydroxybenzoic acid (DHBA) from salicylate was measured in the lungs and plasma to assay for the .OH in juvenile (2 mo), adult (9 mo), and senescent (24 mo) Fischer 344 male rats exposed to clean air, 1 part/million (ppm) ozone, or 2 ppm ozone for 2 h. Similar rates of distribution of salicylic acid in plasma and to the lungs were observed among air control animals of all age groups. Levels of 2,3-DHBA were about twice as high in the lungs of air control senescent rats compared with juvenile and adult rats (P < 0.05). Exposure to ozone resulted in 1.5- to 2-fold elevation of 2,3-DHBA in lungs and plasma of all age groups (P < 0.05), whereas levels of 2,5-DHBA were not changed significantly. There was no effect of age on the magnitude of 2,3-DHBA increase in the lungs or plasma after ozone exposure. The postulated source of .OH is chemical reduction of H2O2, which could be generated from increased age-dependent endogenous oxidant production or the age-independent reaction of ozone or macrophage-derived oxidants with the surfactant lining.

scholarly journals Dendritic spikes in hippocampal granule cells are necessary for long-term potentiation at the perforant path synapse

2018 ◽  
Author(s):  
Sooyun Kim ◽  
Yoonsub Kim ◽  
Suk-Ho Lee ◽  
Won-Kyung Ho
Keyword(s):  
Granule Cells ◽  
Memory Function ◽  
Brain Slices ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
Term Potentiation ◽  
Dendritic Spikes ◽  
Voltage Attenuation ◽  
Synaptic Responses

AbstractLong-term potentiation (LTP) of synaptic responses is essential for hippocampal memory function. Perforant-path (PP) synapses on hippocampal granule cells (GCs) contribute to the formation of associative memories, which are considered the cellular correlates of memory engrams. However, the mechanisms of LTP at these synapses are not well understood. Due to sparse firing activity and the voltage attenuation in their dendrites, it remains unclear how associative LTP at distal synapses occurs. Here we show that NMDA receptor-dependent LTP can be induced at PP-GC synapses without backpropagating action potentials (bAPs) in acute rat brain slices. Dendritic recordings reveal substantial attenuation of bAPs as well as local dendritic Na + ‐spike generation during PP-GC input. Inhibition of Na+ ‐spikes impairs LTP suggesting that LTP at PP-GC synapse requires local Na + ‐spikes. Thus, dendritic spikes are essential for LTP induction at PP-GC synapse and may constitute a key cellular mechanism for memory formation in the dentate gyrus.

scholarly journals The Curious Anti-Pathology of the Wlds Mutation: Paradoxical Postsynaptic Spine Growth Accompanies Delayed Presynaptic Wallerian Degeneration

2021 ◽  
Vol 14 ◽  
Author(s):  
Oswald Steward ◽  
Jennifer M. Yonan ◽  
Paula M. Falk
Keyword(s):  
Wallerian Degeneration ◽  
Granule Cells ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
Synaptic Membrane ◽  
Term Potentiation ◽  
Terminal Degeneration ◽  
Synapse Degeneration ◽  
Degenerating Axons

The Wlds mutation, which arose spontaneously in C57Bl/6 mice, remarkably delays the onset of Wallerian degeneration of axons. This remarkable phenotype has transformed our understanding of mechanisms contributing to survival vs. degeneration of mammalian axons after separation from their cell bodies. Although there are numerous studies of how the Wlds mutation affects axon degeneration, especially in the peripheral nervous system, less is known about how the mutation affects degeneration of CNS synapses. Here, using electron microscopy, we explore how the Wlds mutation affects synaptic terminal degeneration and withering and re-growth of dendritic spines on dentate granule cells following lesions of perforant path inputs from the entorhinal cortex. Our results reveal that substantial delays in the timing of synapse degeneration in Wlds mice are accompanied by paradoxical hypertrophy of spine heads with enlargement of post-synaptic membrane specializations (PSDs) and development of spinules. These increases in the complexity of spine morphology are similar to what is seen following induction of long-term potentiation (LTP). Robust and paradoxical spine growth suggests yet to be characterized signaling processes between amputated but non-degenerating axons and their postsynaptic targets.

scholarly journals The discovery of long-term potentiation

2003 ◽  
Vol 358 (1432) ◽  
pp. 617-620 ◽  
Author(s):  
Terje Lømo
Keyword(s):  
Granule Cells ◽  
Field Potential ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
Term Potentiation ◽  
Basic Reference ◽  
Potential Recording ◽  
Independent Work ◽  
Field Potential Recording

This paper describes circumstances around the discovery of long-term potentiation (LTP). In 1966, I had just begun independent work for the degree of Dr medicinae (PhD) in Per Andersen's laboratory in Oslo after an eighteen-month apprenticeship with him. Studying the effects of activating the perforant path to dentate granule cells in the hippocampus of anaesthetized rabbits, I observed that brief trains of stimuli resulted in increased efficiency of transmission at the perforant path-granule cell synapses that could last for hours. In 1968, Tim Bliss came to Per Andersen's laboratory to learn about the hippocampus and field potential recording for studies of possible memory mechanisms. The two of us then followed up my preliminary results from 1966 and did the experiments that resulted in a paper that is now properly considered to be the basic reference for the discovery of LTP.

scholarly journals Altered Dendritic Integration in Hippocampal Granule Cells of Spatial Learning-Impaired Aged Rats

2008 ◽  
Vol 99 (6) ◽  
pp. 2769-2778 ◽  
Author(s):  
Michael Krause ◽  
Zhiyong Yang ◽  
Geeta Rao ◽  
Frank P. Houston ◽  
C. A. Barnes
Keyword(s):  
Nmda Receptor ◽  
Spatial Learning ◽  
Granule Cells ◽  
Developmental Process ◽  
Perforant Path ◽  
Spatial Learning And Memory ◽  
Aged Rats ◽  
Fischer 344 Rats ◽  
Whole Cell ◽  
Fischer 344

Glutamatergic transmission at central synapses undergoes activity-dependent and developmental changes. In the hippocampal dentate gyrus, the non- N-methyl d-aspartate (NMDA) receptor component of field excitatory postsynaptic potentials (fEPSPs) increases with age in Fischer-344 rats. This effect may not depend on the animal's activity or experience but could be part of the developmental process. Age-dependent differences in synaptic transmission at the perforant path-granule cell synapse may be caused by changes in non-NMDA and NMDA receptor-mediated currents. To test this hypothesis, we compared whole cell excitatory postsynaptic currents (EPSCs) in dentate granule cells evoked by perforant path stimulation in young (3–4 mo) and aged (22–27 mo) Fischer-344 rats using a Cs+-based intracellular solution. Aged animals as a group showed spatial learning and memory deficits in the Morris water maze. Using whole cell recordings, slope conductances of both non-NMDA and NMDA EPSCs at holding potentials −10 to +50 mV were significantly reduced in aged animals and the non-NMDA/NMDA ratio in aged animals was found to be significantly smaller than in young animals. In contrast, we detected no differences in basic electrophysiological parameters, or absolute amplitudes of non-NMDA and NMDA EPSCs. Extracellular Cs+ increased the fEPSP in young slices to a greater degree than was found in the aged slices, while it increased population spikes to a greater degree in the aged rats. Our results not only provide evidence for reduced glutamatergic synaptic responses in Fischer-344 rats but also point to differential changes in Cs+-sensitive dendritic conductances, such as Ih or inwardly rectifying potassium currents, during aging.

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