101
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Korol D, Gold P. Epinephrine converts long-term potentiation from transient to durable form in awake rats. Hippocampus 2007; 18:81-91. [DOI: 10.1002/hipo.20372] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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102
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Abstract
Norepinephrine's role in the dentate gyrus is assessed based on a review of what is known about its innervation and receptor patterns and its functional effects at both cellular and behavioral levels. The data support seven hypotheses: (1) Norepinephrine's functional actions are primarily mediated by beta adrenoceptors and include electrophysiological enhancement of responses to excitatory input and glycogenolytic metabolic support of excitatory synaptic activity. (2) At the cellular level, locus coeruleus burst release of norepinephrine transiently inhibits feedforward interneurons and either excites or inhibits subpopulations of feedback interneurons. Consistent with reduced feedforward inhibition, granule cell firing is transiently increased. Concomitant EEG effects include transient increases in theta power and decreases in beta and gamma power. (3) Norepinephrine selectively promotes the processing of medial perforant path spatial input. This effect is mediated both through short- and long-term potentiation of cell excitability and through delayed potentiation of synaptic input. A critical level of norepinephrine release is required for long-term effects to norepinephrine alone. Norepinephrine release switches early phase frequency-induced long-term potentiation of perforant path input to an enduring late phase form and can reinstate decayed long-term potentiation. Norepinephrine also promotes frequency-induced potentiation of granule cell output at the mossy fiber to CA3 connection. (4) Local increases in norepinephrine accompany glutamate release and release of other neurotransmitters providing a mechanism for norepinephrine enhancement effects independent of locus coeruleus firing. (5) Stimuli, such as novelty and reward and punishment, which activate locus coeruleus neurons, enhance responses to medial perforant path input and engage late phase frequency-induced long-term potentiation through beta adrenoceptor activation. (6) Behavioral studies are consistent with the mechanistic evidence for a norepinephrine role in promoting learning and memory and assisting retrieval. (7) The overall profile suggests lower levels of norepinephrine may facilitate pattern completion or memory retrieval while higher levels would recruit global remapping and promote long-term episodic memory.
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Affiliation(s)
- Carolyn W Harley
- Department of Psychology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
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103
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Dringenberg HC, Kuo MC. Cholinergic, histaminergic, and noradrenergic regulation of LTP stability and induction threshold: cognitive implications. EXS 2006; 98:165-83. [PMID: 17019888 DOI: 10.1007/978-3-7643-7772-4_9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Hans C Dringenberg
- Department of Psychology, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario K7L 3N6, Canada.
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104
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Yang CH, Huang CC, Hsu KS. Novelty exploration elicits a reversal of acute stress-induced modulation of hippocampal synaptic plasticity in the rat. J Physiol 2006; 577:601-15. [PMID: 17008368 PMCID: PMC1890448 DOI: 10.1113/jphysiol.2006.120386] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Acute behavioural stress has been recognized as a strong influence on the inducibility of hippocampal long-term synaptic plasticity. We have reported previously that in adult male rats, acute behavioural stress impairs long-term potentiation (LTP) but enhances long-term depression (LTD) in the hippocampal CA1 region. In this study we report that the effects of stress on LTP and LTD were reversed when animals were introduced into a novel 'stimulus-rich' environment immediately after the stress. Novelty exploration-induced reversal of stress effects was prevented when the animals were given the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid, the cholinergic antagonist atropine and the protein phosphatase (PP) 2B inhibitors cyclosporin A and cypermethrin, but not the alpha1-adrenergic antagonist prazosin, the beta-adrenergic antagonist propranolol or the PP1/2A inhibitor okadaic acid, respectively before being subjected to the novel environment. In addition, the ability of novelty exploration to reverse the stress effects was mimicked by a direct application of the cholinergic agonist carbachol. Exposure to the novel environment following stress was accompanied by the activation of both PP2B and striatal-enriched tyrosine phosphatase (STEP). Taken together, these findings suggest that the activation of the cholinergic system and, in turn, the triggering of an NMDA receptor-mediated activation of PP2B to increase STEP activity appear to mediate the novelty exploration-induced reversal of stress-related modulation of hippocampal long-term synaptic plasticity.
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Affiliation(s)
- Chih-Hao Yang
- Department of Pharmacology, College of Medicine, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan
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105
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Bunzeck N, Düzel E. Absolute coding of stimulus novelty in the human substantia nigra/VTA. Neuron 2006; 51:369-79. [PMID: 16880131 DOI: 10.1016/j.neuron.2006.06.021] [Citation(s) in RCA: 282] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 05/11/2006] [Accepted: 06/21/2006] [Indexed: 10/24/2022]
Abstract
Novelty exploration can enhance hippocampal plasticity in animals through dopaminergic neuromodulation arising in the substantia nigra/ventral tegmental area (SN/VTA). This enhancement can outlast the exploration phase by several minutes. Currently, little is known about dopaminergic novelty processing and its relationship to hippocampal function in humans. In two functional magnetic resonance imaging (fMRI) studies, SN/VTA activations in humans were indeed driven by stimulus novelty rather than other forms of stimulus salience such as rareness, negative emotional valence, or targetness of familiar stimuli, whereas hippocampal responses were less selective. SN/VTA novelty responses were scaled according to absolute rather than relative novelty in a given context, unlike adaptive SN/VTA responses recently reported for reward outcome in animal studies. Finally, novelty enhanced learning and perirhinal/parahippocampal processing of familiar items presented in the same context. Thus, the human SN/VTA can code absolute stimulus novelty and might contribute to enhancing learning in the context of novelty.
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Affiliation(s)
- Nico Bunzeck
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London, WC1N 3AR, United Kingdom
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106
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Ahmed T, Frey JU, Korz V. Long-term effects of brief acute stress on cellular signaling and hippocampal LTP. J Neurosci 2006; 26:3951-8. [PMID: 16611811 PMCID: PMC6673904 DOI: 10.1523/jneurosci.4901-05.2006] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 11/21/2022] Open
Abstract
In a previous study, we reported that a brief exposure to swim stress transforms an electrically induced, protein synthesis-independent early long-term potentiation (early LTP) into a protein synthesis-dependent late LTP ["reinforcement of LTP" in the hippocampal dentate gyrus (DG)] (Korz and Frey, 2003). This transformation depends on activation of mineralocorticoid receptors (MRs) by corticosterone, and on intact basolateral amygdala (BLA) function. Here, we demonstrate that a brief swim experience results in lasting changes in levels of hippocampal cellular signaling molecules that are known to be involved in the induction of late LTP. Within the DG, MRs were rapidly upregulated, whereas glucocorticoid receptor (GR) levels were elevated with a 3 h delay. Levels of phosphorylated mitogen-activated protein kinase 2 (pMAPK2) and p38 MAPK, as well as phosphorylated calcium/calmodulin-dependent protein kinase II (pCaMKII) were enhanced shortly after swim stress and remained elevated until 24 h, whereas levels of phosphorylated cAMP response element-binding protein (pCREB) remained unchanged. MR and GR were upregulated with a longer delay within the CA1 region, whereas levels of pMAPK2 and p38MAPK were rapidly increased, but the former returned to basal levels after 3 h. Levels of pCREB and pCaMKII were maintained in an enhanced state after swim stress. DG-LTP reinforcement requires a serotonergic but not dopaminergic heterosynaptic receptor activation that probably mediates the BLA-dependent modulation of LTP under stress. Thus, molecular alterations induced by specific stress resemble late LTP-related molecular changes. These changes, in interaction with stress-specific heterosynaptic processes, may support the transformation of early LTP into late LTP. The results contribute to the understanding of the rapid consolidation of cellular and possibly systemic memories triggered by stress.
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107
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Roozendaal B, Okuda S, Van der Zee EA, McGaugh JL. Glucocorticoid enhancement of memory requires arousal-induced noradrenergic activation in the basolateral amygdala. Proc Natl Acad Sci U S A 2006; 103:6741-6. [PMID: 16611726 PMCID: PMC1458951 DOI: 10.1073/pnas.0601874103] [Citation(s) in RCA: 359] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Considerable evidence indicates that glucocorticoid hormones enhance the consolidation of long-term memories for emotionally arousing experiences but not that for less arousing or neutral information. However, previous studies have not determined the basis of such arousal-induced selectivity. Here we report the finding that endogenous noradrenergic activation of the basolateral complex of the amygdala (BLA) induced by emotional arousal is essential in enabling glucocorticoid memory enhancement. Corticosterone administered immediately after object recognition training enhanced 24-h memory of naïve male rats but not that of rats previously habituated to the training context in order to reduce novelty-induced emotional arousal. The beta-adrenoceptor antagonist propranolol administered either systemically or into the BLA blocked the corticosterone-induced memory enhancement. Further, in habituated rats, corticosterone activated BLA neurons, as assessed by phosphorylated cAMP response element binding (pCREB) immunoreactivity levels, and enhanced memory only when norepinephrine release was stimulated by administration of the alpha(2)-adrenoceptor antagonist yohimbine. These findings strongly suggest that synergistic actions of glucocorticoids and emotional arousal-induced noradrenergic activation of the BLA constitute a neural mechanism by which glucocorticoids may selectively enhance memory consolidation for emotionally arousing experiences.
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Affiliation(s)
- Benno Roozendaal
- *Center for the Neurobiology of Learning and Memory, and Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800
- To whom correspondence may be addressed. E-mail:
or
| | - Shoki Okuda
- *Center for the Neurobiology of Learning and Memory, and Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800
- CNS Disorder Research, Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., Tsukuba, Ibaraki 300-2611, Japan; and
| | - Eddy A. Van der Zee
- Department of Molecular Neurobiology, University of Groningen, P.O. Box 14, 9750 AA, Haren, The Netherlands
| | - James L. McGaugh
- *Center for the Neurobiology of Learning and Memory, and Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800
- To whom correspondence may be addressed. E-mail:
or
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108
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Sanberg CD, Jones FL, Do VH, Dieguez D, Derrick BE. 5-HT1a receptor antagonists block perforant path-dentate LTP induced in novel, but not familiar, environments. Learn Mem 2006; 13:52-62. [PMID: 16452654 PMCID: PMC1360133 DOI: 10.1101/lm.126306] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Numerous studies suggest roles for monoamines in modulating long-term potentiation (LTP). Previously, we reported that both induction and maintenance of perforant path-dentate gyrus LTP is enhanced when induced while animals explore novel environments. Here we investigate the contribution of serotonin and 5-HT1a receptors to the novelty-mediated enhancement of LTP. In freely moving animals, systemic administration of the selective 5-HT1a antagonist WAY-100635 (WAY) attenuated LTP in a dose-dependent manner when LTP was induced while animals explored novel cages. In contrast, LTP was completely unaffected by WAY when induced in familiar environments. LTP was also blocked in anesthetized animals by direct application of WAY to the dentate gyrus, but not to the median raphe nucleus (MRN), suggesting the effect of systemic WAY is mediated by a block of dentate 5-HT1a receptors. Paradoxically, systemic administration of the 5-HT1a agonist 8-OH-DPAT also attenuated LTP. This attenuation was mimicked in anesthetized animals following application of 8-OH-DPAT to the MRN, but not the dentate gyrus. In addition, application of a 5-HT1a agonist to the dentate gyrus reduced somatic GABAergic inhibition. Because serotonergic projections from the MRN terminate on dentate inhibitory interneurons, these data suggest 5-HT1a receptors contribute to LTP induction via inhibition of GABAergic interneurons. Moreover, activation of raphe 5-HT1a autoreceptors, which inhibits serotonin release, attenuated LTP induction even in familiar environments. This suggests that serotonin normally contributes to dentate LTP induction in a variety of behavioral states. Together, these data suggest that serotonin and dentate 5-HT1a receptors play a permissive role in dentate LTP induction, particularly in novel conditions, and presumably, during the encoding of novel, hippocampus-relevant information.
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Affiliation(s)
- Cyndy Davis Sanberg
- The Department of Biology, The Cajal Neuroscience Research Institute, The University of Texas at San Antonio, Texas 78249, USA
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109
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Korz V, Frey JU. Bidirectional modulation of hippocampal long-term potentiation under stress and no-stress conditions in basolateral amygdala-lesioned and intact rats. J Neurosci 2006; 25:7393-400. [PMID: 16093390 PMCID: PMC6725292 DOI: 10.1523/jneurosci.0910-05.2005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hippocampal long-term potentiation (LTP) is widely considered as a cellular model for learning and memory formation. We have shown previously that protein synthesis-independent, early dentate gyrus (DG) LTP, lasting approximately 4-5 h, can be transformed into a late-LTP with a duration of > or = 24 h by a brief acute swim stress experience (high-stress condition). This reinforcement requires the activation of mineralocorticoid receptors and protein synthesis. The basolateral amygdala (BLA) is known to modulate glucocorticoid effects on the consolidation of spatial/contextual memory via a beta-adrenergic mechanism. Interestingly, hippocampal DG-LTP can also be indirectly modulated by beta-adrenergic and cholinergic/muscarinergic processes. Here, we show that the reinforcement of early-DG-LTP under high-stress conditions depends on the processing of novel spatial/contextual information. Furthermore, this reinforcement was blocked in BLA-lesioned animals compared with sham-operated and intact controls; however, it was not dependent on beta-adrenergic or cholinergic/muscarinergic receptor activation. In contrast, under low-stress conditions, the induction of late-LTP in BLA-lesioned animals is facilitated, and this facilitation, again, was dependent on beta-adrenergic activation. The data suggest that DG-LTP maintenance can be influenced by the BLA through different mechanisms: a short-lasting corticosterone-dependent and beta-adrenergic-independent mechanism and a long-lasting mechanism that facilitated hippocampal beta-adrenergic mechanisms.
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Affiliation(s)
- Volker Korz
- Department of Neurophysiology, Leibniz-Institute for Neurobiology, D-39118 Magdeburg, Germany.
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110
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Almaguer-Melian W, Rosillo JC, Frey JU, Bergado JA. Subcortical deafferentation impairs behavioral reinforcement of long-term potentiation in the dentate gyrus of freely moving rats. Neuroscience 2006; 138:1083-8. [PMID: 16426765 DOI: 10.1016/j.neuroscience.2005.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 11/17/2005] [Accepted: 12/01/2005] [Indexed: 11/29/2022]
Abstract
Long-term potentiation is a form of neural functional plasticity which has been related with memory formation and recovery of function after brain injury. Previous studies have shown that a transient early-long-term potentiation can be prolonged by direct stimulation of distinct brain areas, or behavioral stimuli with a high motivational content. The basolateral amygdala and other subcortical structures, like the medial septum and the locus coeruleus, are involved in mediating the reinforcing effect. We have previously shown that the lesion of the fimbria-fornix--the main entrance of subcortical afferents to the hippocampus--abolishes the reinforcing basolateral amygdala-effects on long-term potentiation in the dentate gyrus in vivo. It remains to be investigated, however, if such subcortical afferents may also be important for behavioral reinforcement of long-term potentiation. Young-adult (8 weeks) Sprague-Dawley male rats were fimbria-fornix-transected under anesthesia, and electrodes were implanted at the dentate gyrus and the perforant path. One week after surgery the freely moving animals were studied. Fimbria-fornix-lesion reduced the ability of the animals to develop long-term potentiation when a short pulse duration was used for tetanization (0.1 ms per half-wave of a biphasic stimulus), whereas increasing the pulse duration to 0.2 ms per half-wave during tetanization resulted in a transient early-long-term potentiation lasting about 4 h in the lesioned animals, comparable to that obtained in non-lesioned or sham-operated control rats. In water-deprived (24 h) control animals, i.e. in non-lesioned and sham-operated rats, early-long-term potentiation could be behaviorally reinforced by drinking 15 min after tetanization. However, in fimbria-fornix-lesioned animals long-term potentiation-reinforcement by drinking was not detected. This result indicates that the effect of behavioral-motivational stimuli to reinforce long-term potentiation is mediated by subcortical, heterosynaptic afferents.
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Affiliation(s)
- W Almaguer-Melian
- Centro Internacional de Restauración Neurológica, Ave. 25 # 15805, Cubanacán, Playa 11300, Ciudad de La Habana, Cuba
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111
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Straube T, Glauer M, Dilger S, Mentzel HJ, Miltner WHR. Effects of cognitive-behavioral therapy on brain activation in specific phobia. Neuroimage 2005; 29:125-35. [PMID: 16087353 DOI: 10.1016/j.neuroimage.2005.07.007] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Revised: 06/03/2005] [Accepted: 07/05/2005] [Indexed: 12/30/2022] Open
Abstract
Little is known about the effects of successful psychotherapy on brain function in subjects with anxiety disorders. The present study aimed to identify changes in brain activation following cognitive-behavioral therapy (CBT) in subjects suffering from specific phobia. Using functional magnetic resonance imaging (fMRI), brain activation to spider videos was measured in 28 spider phobic and 14 healthy control subjects. Phobics were randomly assigned to a therapy-group (TG) and a waiting-list control group (WG). Both groups of phobics were scanned twice. Between scanning sessions, CBT was given to the TG. Before therapy, brain activation did not differ between both groups of phobics. As compared to control subjects, phobics showed greater responses to spider vs. control videos in the insula and anterior cingulate cortex (ACC). CBT strongly reduced phobic symptoms in the TG while the WG remained behaviorally unchanged. In the second scanning session, a significant reduction of hyperactivity in the insula and ACC was found in the TG compared to the WG. These results propose that increased activation in the insula and ACC is associated with specific phobia, whereas an attenuation of these brain responses correlates with successful therapeutic intervention.
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Affiliation(s)
- Thomas Straube
- Department of Biological and Clinical Psychology, Friedrich-Schiller-University, Am Steiger 3,1, D-07743 Jena, Germany.
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112
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Lisman JE, Grace AA. The hippocampal-VTA loop: controlling the entry of information into long-term memory. Neuron 2005; 46:703-13. [PMID: 15924857 DOI: 10.1016/j.neuron.2005.05.002] [Citation(s) in RCA: 1340] [Impact Index Per Article: 70.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this article we develop the concept that the hippocampus and the midbrain dopaminergic neurons of the ventral tegmental area (VTA) form a functional loop. Activation of the loop begins when the hippocampus detects newly arrived information that is not already stored in its long-term memory. The resulting novelty signal is conveyed through the subiculum, accumbens, and ventral pallidum to the VTA where it contributes (along with salience and goal information) to the novelty-dependent firing of these cells. In the upward arm of the loop, dopamine (DA) is released within the hippocampus; this produces an enhancement of LTP and learning. These findings support a model whereby the hippocampal-VTA loop regulates the entry of information into long-term memory.
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Affiliation(s)
- John E Lisman
- Department of Biology, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, USA.
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113
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Davis CD, Jones FL, Derrick BE. Novel environments enhance the induction and maintenance of long-term potentiation in the dentate gyrus. J Neurosci 2005; 24:6497-506. [PMID: 15269260 PMCID: PMC6729872 DOI: 10.1523/jneurosci.4970-03.2004] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The induction of long-term potentiation (LTP) in the hippocampal formation can be modulated by different behavioral states. However, few studies have addressed modulation of LTP during behavioral states in which the animal is likely acquiring new information. Here, we demonstrate that both the induction and the longevity of LTP in the dentate gyrus are enhanced when LTP is induced during the initial exploration of a novel environment. These effects are independent from locomotor activity, changes in brain temperature, and theta rhythm. Previous exposure to the novel environment attenuated this enhancement, suggesting that the effects of novelty habituate with familiarity. LTP longevity also was enhanced when induced in familiar environments containing novel objects. Together, these data indicate that both LTP induction and maintenance are enhanced when LTP is induced while rats investigate novel stimuli. We suggest that novelty initiates a transition of the hippocampal formation to a mode that is particularly conducive to synaptic plasticity, a process that could allow for new learning while preserving the stability of previously stored information. In addition, LTP induced in novel environments elicited a sustained late LTP. This suggests that a single synaptic population can display distinct profiles of LTP maintenance and that this depends on the animal's behavioral state during its induction. Furthermore, the duration of LTP enhanced by novelty parallels the time period during which the hippocampal formation is thought necessary for memory, consistent with the view that dentate LTP is of a duration sufficient to sustain memory in the hippocampal formation.
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Affiliation(s)
- Cyndy D Davis
- Department of Biology and Cajal Neuroscience Research Center, The University of Texas at San Antonio, San Antonio, Texas 78249-0662, USA
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114
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Uzakov S, Frey JU, Korz V. Reinforcement of rat hippocampal LTP by holeboard training. Learn Mem 2005; 12:165-71. [PMID: 15774946 PMCID: PMC1074335 DOI: 10.1101/lm.89305] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2004] [Accepted: 12/16/2004] [Indexed: 11/25/2022]
Abstract
Hippocampal long-term potentiation (LTP) can be dissociated in early-LTP lasting 4-5 h and late-LTP with a duration of more than 8 h, the latter of which requires protein synthesis and heterosynaptic activity during its induction. Previous studies in vivo have shown that early-LTP in the dentate gyrus can protein synthesis-dependently be transformed (reinforced) into late-LTP by the association of arousing novel environmental stimuli. Here we show that consolidation of spatial memory also reinforces early-LTP in the dentate gyrus. Both memory consolidation and LTP-reinforcement depend on protein synthesis. Four groups of animals were trained by five, seven, eight or 10 trials, respectively, to recognize a fixed pattern of baited holes. The last trial was performed 15 min after tetanus. Errors of long-term reference memory during the last trial were significantly decreased only in the eight- and 10-trial experimental groups compared to pseudo-trained animals. In correlation to this learning effect we found a reinforcement of early-LTP only in these experimental groups compared to controls. The data suggest that the synthesis of new proteins required for spatial reference-memory formation also contributes to LTP maintenance in the hippocampal dentate gyrus.
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Affiliation(s)
- Shukhrat Uzakov
- Department of Neurophysiology, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany
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115
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Wittmann BC, Schott BH, Guderian S, Frey JU, Heinze HJ, Düzel E. Reward-Related fMRI Activation of Dopaminergic Midbrain Is Associated with Enhanced Hippocampus- Dependent Long-Term Memory Formation. Neuron 2005; 45:459-67. [PMID: 15694331 DOI: 10.1016/j.neuron.2005.01.010] [Citation(s) in RCA: 481] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 12/22/2004] [Accepted: 01/07/2005] [Indexed: 11/20/2022]
Abstract
Long-term potentiation in the hippocampus can be enhanced and prolonged by dopaminergic inputs from midbrain structures such as the substantia nigra. This improved synaptic plasticity is hypothesized to be associated with better memory consolidation in the hippocampus. We used a condition that reliably elicits a dopaminergic response, reward anticipation, to study the relationship between activity of dopaminergic midbrain areas and hippocampal long-term memory in healthy adults. Pictures of object drawings that predicted monetary reward were associated with stronger fMRI activity in reward-related brain areas, including the substantia nigra, compared with non-reward-predicting pictures. Three weeks later, recollection and source memory were better for reward-predicting than for non-reward-predicting pictures. FMRI activity in the hippocampus and the midbrain was higher for reward-predicting pictures that were later recognized compared with later forgotten pictures. These data are consistent with the hypothesis that activation of dopaminergic midbrain regions enhances hippocampus-dependent memory formation, possibly by enhancing consolidation.
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Affiliation(s)
- Bianca C Wittmann
- Department of Neurology II and , Centre for Advanced Imaging, Otto von Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany
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116
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Gibbs ME, Summers RJ. Contrasting roles for β1, β2 and β3-adrenoceptors in memory formation in the chick. Neuroscience 2005; 131:31-42. [PMID: 15680689 DOI: 10.1016/j.neuroscience.2004.10.036] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2004] [Indexed: 11/24/2022]
Abstract
Noradrenaline plays distinct roles in the modulation and consolidation of memory for one-trial, discriminated, avoidance learning in the chick. We have previously shown that activation of beta2-, beta3- and alpha1-adrenoceptors (ARs) by injection into the multimodal forebrain association region (intermediate medial hyperstriatum ventrale [IMHV] or intermediate medial mesopallium [IMM]) is involved in the consolidation of memory 30 min after training and that activation of alpha2-ARs in the caudate putamen plays a role in the reinforcement of memory leading to consolidation in the IMM (IMHV). In this paper we provide evidence that noradrenaline acts at beta1-ARs in the basal ganglia (lobus parolfactorius or medial striatum) in short-term memory processing immediately post-training and demonstrate inhibition of memory by selective AR antagonists at particular times in the sequential memory processing sequence after training. These results support separate roles for beta2- and beta3-ARs in memory consolidation. Our studies suggest that, as a consequence of the learning experience, noradrenaline acts in different brain regions and at different times in memory processing, to enhance memory through distinct populations of ARs.
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Affiliation(s)
- M E Gibbs
- Department of Pharmacology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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117
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Walling SG, Harley CW. Locus ceruleus activation initiates delayed synaptic potentiation of perforant path input to the dentate gyrus in awake rats: a novel beta-adrenergic- and protein synthesis-dependent mammalian plasticity mechanism. J Neurosci 2004; 24:598-604. [PMID: 14736844 PMCID: PMC6729256 DOI: 10.1523/jneurosci.4426-03.2004] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Norepinephrine, acting through beta-adrenergic receptors, is implicated in mammalian memory. In in vitro and in vivo studies, norepinephrine produces potentiation of the perforant path-dentate gyrus evoked potential; however, the duration and dynamics of norepinephrine-induced potentiation have not been explored over extended time periods. To characterize the long-term effects of norepinephrine on granule cell plasticity, the present study uses glutamatergic activation of the locus ceruleus (LC) to induce release of norepinephrine in the hippocampus of the awake rat and examines the subsequent modulation of the dentate gyrus evoked potential for 3 hr (short term) and 24 hr (long term) after LC activation. LC activation initiates a potentiation of the field EPSP slope observed 24 hr later. This late-phase potentiation of the synaptic potential is not preceded by early phase potentiation, although spike potentiation can be seen both immediately after, and 24 hr after, LC activation. Intracerebroventricular infusion of the beta-adrenergic antagonist, propranolol, or the protein synthesis inhibitor, anisomycin, before LC activation blocks the potentiation of perforant path input observed at 24 hr. The initiation of late-phase synaptic potentiation observed at 24 hr but not at the 3 hr after LC activation parallels the observation of a cAMP- and protein synthesis-dependent long-lasting synaptic facilitation in Aplysia that is not preceded by short-term synaptic facilitation. Locus ceruleus-initiated synaptic potentiation may selectively support long-term, rather than short-term, memory. The observation of selective initiation of long-term synaptic facilitation in a mammalian brain, as in invertebrates, is additional evidence that these two forms of memory depend on separable biological mechanisms.
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Affiliation(s)
- Susan G Walling
- Behavioral Neuroscience, Department of Psychology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X9
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