scholarly journals Temporal and spatial regulation of the expression of BAD2, a MAP kinase phosphatase, during seizure, kindling, and long-term potentiation.

1994 ◽  
Vol 1 (3) ◽  
pp. 180-188
Author(s):  
Z Qian ◽  
M Gilbert ◽  
E R Kandel
Keyword(s):  
Map Kinase ◽  
Specific Activity ◽  
Long Term Potentiation ◽  
Dual Purpose ◽  
Spatial Regulation ◽  
Term Potentiation ◽  
Map Kinase Phosphatase ◽  
Synaptic Changes

Recent studies indicate that stimulation of NMDA receptors in cultured hippocampal cells activates MAP kinase. Although the pathway whereby MAP kinase is activated has been been characterized, little is known about the mechanisms that shut off MAP kinase. In the course of analyzing several immediate-early genes identified previously by differential screen as inducible by seizure activity, we found that one of them, BAD2, encodes dual purpose, threonine/tyrosine phosphates with specific activity directed against MAP kinase (MKP-1). In situ hybridization of BAD2 demonstrates that stimuli that produce seizure, kindling, and long-term potentiation cause a rapid increase in BAD2 mRNA (within 0.5-1 hr after stimulation) that has, in each case, a distinctive pattern of expression in the brain. In these regions, the induction of a MAP kinase-specific phosphatase may provide a negative feedback control associated with long-term synaptic changes.

Novel Scenes Improve Recollection and Recall of Words

2008 ◽  
Vol 20 (7) ◽  
pp. 1250-1265 ◽  
Author(s):  
Daniela B. Fenker ◽  
Julietta U. Frey ◽  
Hartmut Schuetze ◽  
Dorothee Heipertz ◽  
Hans-Jochen Heinze ◽  
...  
Keyword(s):  
Specific Activity ◽  
Activity Patterns ◽  
Long Term Potentiation ◽  
Contextual Memory ◽  
Memory Enhancement ◽  
Term Potentiation ◽  
Outdoor Scenes ◽  
Indoor And Outdoor ◽  
Hippocampus Dependent Memory

Exploring a novel environment can facilitate subsequent hippocampal long-term potentiation in animals. We report a related behavioral enhancement in humans. In two separate experiments, recollection and free recall, both measures of hippocampus-dependent memory formation, were enhanced for words studied after a 5-min exposure to unrelated novel as opposed to familiar images depicting indoor and outdoor scenes. With functional magnetic resonance imaging, the enhancement was predicted by specific activity patterns observed during novelty exposure in parahippocampal and dorsal prefrontal cortices, regions which are known to be linked to attentional orienting to novel stimuli and perceptual processing of scenes. Novelty was also associated with activation of the substantia nigra/ventral tegmental area of the midbrain and the hippocampus, but these activations did not correlate with contextual memory enhancement. These findings indicate remarkable parallels between contextual memory enhancement in humans and existing evidence regarding contextually enhanced hippocampal plasticity in animals. They provide specific behavioral clues to enhancing hippocampus-dependent memory in humans.

Klk8, a multifunctional protease in the brain and skin: analysis of knockout mice

2010 ◽  
Vol 391 (4) ◽  
Author(s):  
Shigetaka Yoshida
Keyword(s):  
Central Nervous System ◽  
Long Term Potentiation ◽  
Term Potentiation ◽  
The Central Nervous System ◽  
Synaptic Changes ◽  
Adhesive Molecules ◽  
High Level ◽  
Activity Dependent ◽  
The Brain

Abstract Klk8 is a tryptic serine protease with limited substrate specificity. Klk8 mRNA is expressed in many developing organs, whereas its expression is confined to limited regions, including the hippocampus, in adults. In the hippocampus, Klk8 is involved in activity-dependent synaptic changes such as long-term potentiation, which was found to be suppressed in Klk8 knockout (KO) mice. Oligodendrocytes only expressed Klk8 mRNA after injury to the central nervous system. The epidermis of the skin is one of the tissues that exhibits a high level of KLK8 expression. Klk8 might be involved in desquamation through the degradation of adhesive molecules that connect layers of the epidermis. Klk8 might thus be involved in tissue development and rearrangement.

scholarly journals Bistable MAP kinase activity: a plausible mechanism contributing to maintenance of late long-term potentiation

2008 ◽  
Vol 294 (2) ◽  
pp. C503-C515 ◽  
Author(s):  
Paul Smolen ◽  
Douglas A. Baxter ◽  
John H. Byrne
Keyword(s):  
Map Kinase ◽  
Dendritic Spine ◽  
Mapk Pathway ◽  
Long Term Potentiation ◽  
Long Term Memory ◽  
Stable States ◽  
Mapk Activity ◽  
Stochastic Fluctuations ◽  
Term Potentiation

Bistability of MAP kinase (MAPK) activity has been suggested to contribute to several cellular processes, including differentiation and long-term synaptic potentiation. A recent model (Markevich NI, Hoek JB, Kholodenko BN. J Cell Biol 164: 353–359, 2004) predicts bistability due to interactions of the kinases and phosphatases in the MAPK pathway, without feedback from MAPK to earlier reactions. Using this model and enzyme concentrations appropriate for neurons, we simulated bistable MAPK activity, but bistability was present only within a relatively narrow range of activity of Raf, the first pathway kinase. Stochastic fluctuations in molecule numbers eliminated bistability for small molecule numbers, such as are expected in the volume of a dendritic spine. However, positive-feedback loops have been posited from MAPK up to Raf activation. One proposed loop in which MAPK directly activates Raf was incorporated into the model. We found that such feedback greatly enhanced the robustness of both stable states of MAPK activity to stochastic fluctuations and to parameter variations. Bistability was robust for molecule numbers plausible for a dendritic spine volume. The upper state of MAPK activity was resistant to inhibition of MEK activation for >1 h, which suggests that inhibitor experiments have not sufficed to rule out a role for persistent MAPK activity in the maintenance of long-term potentiation (LTP). These simulations suggest that persistent MAPK activity and consequent upregulation of translation may contribute to LTP maintenance and to long-term memory. Experiments using a fluorescent MAPK substrate may further test this hypothesis.

[P4-036]: THE NOVEL AMPA RECEPTOR POSITIVE ALLOSTERIC MODULATOR S 47445 RESCUES IN VIVO CA3-CA1 LONG-TERM POTENTIATION AND STRUCTURAL SYNAPTIC CHANGES IN MIDDLE-AGED MICE

2017 ◽  
Vol 13 (7S_Part_26) ◽  
pp. P1270-P1270
Author(s):  
Sylvie Bretin ◽  
Albert Giralt ◽  
María Ángeles Gómez-Climent ◽  
Rafael Alcalá ◽  
Jose Maria Delgado-Garcia ◽  
...  
Keyword(s):  
Ampa Receptor ◽  
Long Term Potentiation ◽  
Allosteric Modulator ◽  
The Novel ◽  
Positive Allosteric Modulator ◽  
Aged Mice ◽  
Term Potentiation ◽  
Synaptic Changes

A Statistical Theory of Long-Term Potentiation and Depression

2001 ◽  
Vol 13 (1) ◽  
pp. 87-111 ◽  
Author(s):  
John M. Beggs
Keyword(s):  
Response Curve ◽  
Long Term Potentiation ◽  
Synaptic Strength ◽  
Excitatory Synapses ◽  
Field Potentials ◽  
Postsynaptic Activity ◽  
Term Potentiation ◽  
Synaptic Changes ◽  
Cortical Slices

The synaptic phenomena of long-term potentiation (LTP) and long-term depression (LTD) have been intensively studied for over twenty-five years. Although many diverse aspects of these forms of plasticity have been observed, no single theory has offered a unifying explanation for them. Here, a statistical “bin” model is proposed to account for a variety of features observed in LTP and LTD experiments performed with field potentials in mammalian cortical slices. It is hypothesized that long-term synaptic changes will be induced when statistically unlikely conjunctions of pre- and postsynaptic activity occur. This hypothesis implies that finite changes in synaptic strength will be proportional to information transmitted by conjunctions and that excitatory synapses will obey a Hebbian rule (Hebb, 1949). Using only one set of constants, the bin model offers an explanation as to why synaptic strength decreases in a decelerating manner during LTD induction (Mulkey & Malenka, 1992); why the induction protocols for LTP and LTD are asymmetric (Dudek & Bear, 1992; Mulkey & Malenka, 1992); why stimulation over a range of frequencies produces a frequency-response curve similar to that proposed by the BCM theory (Bienenstock, Cooper, & Munro, 1982; Dudek & Bear, 1992); and why this curve would shift as postsynaptic activity is changed (Kirkwood, Rioult, & Bear, 1996). In addition, the bin model offers an alternative to the BCM theory by predicting that changes in postsynaptic activity will produce vertical shifts in the curve rather than merely horizontal shifts.

scholarly journals Stress enhances fear by forming new synapses with greater capacity for long-term potentiation in the amygdala

2014 ◽  
Vol 369 (1633) ◽  
pp. 20130151 ◽  
Author(s):  
Aparna Suvrathan ◽  
Sharath Bennur ◽  
Supriya Ghosh ◽  
Anupratap Tomar ◽  
Shobha Anilkumar ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Conditioned Fear ◽  
Brain Area ◽  
Long Term Potentiation ◽  
Silent Synapses ◽  
Term Potentiation ◽  
Emotional Behaviour ◽  
Synaptic Changes ◽  
And Function

Prolonged and severe stress leads to cognitive deficits, but facilitates emotional behaviour. Little is known about the synaptic basis for this contrast. Here, we report that in rats subjected to chronic immobilization stress, long-term potentiation (LTP) and NMDA receptor (NMDAR)-mediated synaptic responses are enhanced in principal neurons of the lateral amygdala, a brain area involved in fear memory formation. This is accompanied by electrophysiological and morphological changes consistent with the formation of ‘silent synapses’, containing only NMDARs. In parallel, chronic stress also reduces synaptic inhibition. Together, these synaptic changes would enable amygdalar neurons to undergo further experience-dependent modifications, leading to stronger fear memories. Consistent with this prediction, stressed animals exhibit enhanced conditioned fear. Hence, stress may leave its mark in the amygdala by generating new synapses with greater capacity for plasticity, thereby creating an ideal neuronal substrate for affective disorders. These findings also highlight the unique features of stress-induced plasticity in the amygdala that are strikingly different from the stress-induced impairment of structure and function in the hippocampus.

scholarly journals The fate of hippocampal synapses depends on the sequence of plasticity-inducing events

2018 ◽  
Author(s):  
J. Simon Wiegert ◽  
Mauro Pulin ◽  
Christine E. Gee ◽  
Thomas G. Oertner
Keyword(s):  
Hippocampal Slice ◽  
Specific Activity ◽  
Activity Patterns ◽  
Long Term Potentiation ◽  
Information Storage ◽  
Two Photon ◽  
Term Potentiation ◽  
Hippocampal Synapses ◽  
Activity Dependent

AbstractSynapses change their strength in response to specific activity patterns. This functional plasticity is assumed to be the brain’s primary mechanism for information storage. We used optogenetic stimulation of rat hippocampal slice cultures to induce long-term potentiation (LTP), long-term depression (LTD), or both forms of plasticity in sequence. Two-photon imaging of spine calcium signals allowed us to identify stimulated synapses and to follow their fate for the next 7 days. We found that plasticity-inducing protocols affected the synapse’s chance for survival: LTP increased synaptic stability, LTD destabilized synapses, and the effect of the last stimulation protocol was dominant over earlier stimulations. Interestingly, most potentiated synapses were resistant to depression-inducing protocols delivered 24 hours later. Our findings suggest that activity-dependent changes in the transmission strength of individual synapses are transient, but have long-lasting consequences for synaptic lifetime.

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