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Schulz K, Korz V. Hippocampal testosterone relates to reference memory performance and synaptic plasticity in male rats. Front Behav Neurosci 2010; 4:187. [PMID: 21188275 PMCID: PMC3006668 DOI: 10.3389/fnbeh.2010.00187] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 12/01/2010] [Indexed: 12/12/2022] Open
Abstract
Steroids are important neuromodulators influencing cognitive performance and synaptic plasticity. While the majority of literature concerns adrenal- and gonadectomized animals, very little is known about the “natural” endogenous release of hormones during learning. Therefore, we measured blood and brain (hippocampus, prefrontal cortex) testosterone, estradiol, and corticosterone concentrations of intact male rats undergoing a spatial learning paradigm which is known to reinforce hippocampal plasticity. We found significant modulations of all investigated hormones over the training course. Corticosterone and testosterone were correlated manifold with behavior, while estradiol expressed fewer correlations. In the recall session, testosterone was tightly coupled to reference memory (RM) performance, which is crucial for reinforcement of synaptic plasticity in the dentate gyrus. Intriguingly, prefrontal cortex and hippocampal levels related differentially to RM performance. Correlations of testosterone and corticosterone switched from unspecific activity to specific cognitive functions over training. Correspondingly, exogenous application of testosterone revealed different effects on synaptic and neuronal plasticity in trained versus untrained animals. While hippocampal long-term potentiation (LTP) of the field excitatory postsynaptic potential (fEPSP) was prolonged in untrained rats, both the fEPSP- and the population spike amplitude (PSA)-LTP was impaired in trained rats. Behavioral performance was unaffected, but correlations of hippocampal field potentials with behavior were decoupled in treated rats. The data provide important evidence that besides adrenal, also gonadal steroids play a mechanistic role in linking synaptic plasticity to cognitive performance.
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Yavich L, Jäkälä P, Tanila H. Abnormal compartmentalization of norepinephrine in mouse dentate gyrus in alpha-synuclein knockout and A30P transgenic mice. J Neurochem 2006; 99:724-32. [PMID: 16824047 DOI: 10.1111/j.1471-4159.2006.04098.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the dentate gyrus of the mouse hippocampus, presynaptic recruitment of norepinephrine in response to repeated-burst stimulation can be described in terms of an interaction between storage and readily releasable pools. The dynamics of this interaction depends on neuronal activity (bursting), so that the higher the demand for norepinephrine, the faster it is delivered from the storage pool. We also found that alpha-synuclein, a presynaptic protein that plays a crucial role in dopamine compartmentalization in the striatum, is also involved in the compartmentalization of norepinephrine in the dentate gyrus. Experiments in transgenic mice with modified or absent alpha-synuclein revealed that the familial Parkinson's disease-linked alpha-synuclein mutation A30P can cause selective changes in the function of noradrenergic terminals. Addition of mutated human alpha-synuclein abolished the normal norepinephrine mobilization. There were no compensatory mechanisms available in the norepinephrine presynaptic terminals. In contrast, deletion of mouse alpha-synuclein is compensated for by increased vesicle transport from the storage pool. The effects are essentially the same as previously reported for dopaminergic terminals in the striatum, indicating that the important role of alpha-synuclein in neurotransmitter mobilization is not limited to dopaminergic terminals.
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Affiliation(s)
- Leonid Yavich
- Department of Pharmacology and Toxicology, University of Kuopio, Finland.
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Yavich L, Jäkälä P, Tanila H. Noradrenaline overflow in mouse dentate gyrus following locus coeruleus and natural stimulation: real-time monitoring by in vivo voltammetry. J Neurochem 2005; 95:641-50. [PMID: 16248883 DOI: 10.1111/j.1471-4159.2005.03390.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pattern of catecholaminergic innervation of the dentate gyrus (DG) of the hippocampus, particularly the relatively dense and selective noradrenergic input, creates favourable conditions for real-time monitoring of noradrenaline (NA) release following stimulation of the locus coeruleus (LC) by in vivo voltammetry. Two electrochemically active species with different temporal characteristics were registered in the DG following electrical stimulation of the LC. Several approaches, including testing of anatomical and pharmacological specificity, coating of microelectrodes with Nafion and use of fast cyclic voltammetry, were used to verify the characteristics of electrochemical responses. The first sharp peak that appeared immediately during stimulation was definitely associated with NA overflow. The second late peak was possibly attributable to ascorbic acid. We examined the characteristics of alpha-2 adrenoceptor regulation of NA release in the DG, and showed for the first time that noradrenergic terminals resemble dopaminergic terminals in their mechanisms of increasing the refilling rate of the readily releasable pool following stimulation repeated at short intervals. Amperometric registration of NA in the DG was complicated by interference with electrical activity of hippocampus. This interference could be used, after appropriate filtration, for simultaneous recording from the same microelectrode of NA release and electrical activity of the hippocampus.
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Affiliation(s)
- Leonid Yavich
- Department of Pharmacology and Toxicology, Universtiy of Kuopio, Kuopio, Finland.
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Abstract
Long-term potentiation (LTP) at the basal-dendritic synapses of CA1 pyramidal cells was induced by a single 200 Hz stimulation train (0.5-1 sec duration) in freely behaving rats during one of four behavioral states: awake-immobility (IMM), walking, slow-wave sleep (SWS), and rapid eye movement sleep (REM). Field EPSPs generated by basal-dendritic excitation of CA1 were recorded before and up to 1 d after the tetanus. After a tetanus during any behavioral state, basal-dendritic LTP was >170% of the baseline for the first hour after the tetanus and decayed to approximately 120% 1 d after. LTP induced during walking was significantly larger than that induced during IMM, SWS, or REM, which had similar LTP magnitudes. To test the hypothesis that septohippocampal cholinergic activity enhanced LTP during walking as compared with IMM, rats were either pretreated with muscarinic cholinergic antagonist scopolamine or injected with IgG192-saporin in the medial septum to selectively lesion cholinergic septohippocampal neurons. Pretreatment with scopolamine decreased the LTP induced during walking but did not affect that induced during IMM, such that the difference between the LTP induced during walking and IMM was abolished after scopolamine. Rats injected with IgG192-saporin showed no difference in the LTP induced during walking and IMM, and scopolamine did not reduce the LTP during walking. In contrast, sham-lesion rats showed larger LTP induced during walking than IMM, and the LTP induced during walking was attenuated by scopolamine. This is the first demonstration of an enhancement of hippocampal LTP by physiologically activated cholinergic inputs.
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Straube T, Frey JU. Involvement of beta-adrenergic receptors in protein synthesis-dependent late long-term potentiation (LTP) in the dentate gyrus of freely moving rats: the critical role of the LTP induction strength. Neuroscience 2003; 119:473-9. [PMID: 12770561 DOI: 10.1016/s0306-4522(03)00151-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have investigated the requirement of beta-adrenergic receptor activation and protein synthesis for the induction and specifically for the maintenance of long-term potentiation (LTP) in the dentate gyrus of freely moving rats in dependency on different LTP-induction procedures. Three tetanization paradigms were used: a relatively weak protocol A (10 bursts of 15 biphasic pulses at 200 Hz; 10-s interburst interval; 0.2-ms pulse width per phase), a stronger protocol B (as protocol A but 20 bursts and 0.25-ms pulse width) and, as the strongest condition, protocol C (2 times protocol B; inter-tetanus interval: 5 min). All protocols led to robust late-LTP in control animals. Late- but not early-LTP was protein synthesis-dependent under all tetanization conditions as indicated by the absence of long-lasting LTP when the protein synthesis inhibitor anisomycin was applied before tetanization. Application of the beta-adrenergic receptor antagonist propranolol before LTP induction prevented late-LTP when either protocol A or B but not when protocol C was used. Thus, repeated strong tetanization can compensate for the loss of beta-adrenergic receptor activation. We suggest that the results could provide a link to cellular mechanisms of memory consolidation in respect to the strength and relevance of the incoming sensory information during learning.
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Affiliation(s)
- T Straube
- Leibniz-Institute for Neurobiology, Department of Neurophysiology, Brenneckestrasse 6, D-39118, Magdeburg, Germany.
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Abstract
Basolateral amygdala (BLA) activation by emotional arousal modulates memory-related processes in the hippocampus. We have shown (Akirav and Richter-Levin, 1999b) that activating the BLA before perforant path (PP) tetanization has a biphasic effect on hippocampal plasticity; priming the BLA immediately before PP tetanization results in the enhancement of dentate gyrus (DG) long-term potentiation (LTP) (an "emotional tag"), whereas stimulation in a spaced interval results in the suppression of DG-LTP. Here, we aimed to elucidate the mechanisms underlying BLA modulation of DG-LTP and specifically to examine whether the stress hormones norepinephrine (NE) and corticosterone (CORT) are main mediators of the BLA biphasic effects. We found that the BLA affects hippocampal plasticity in a complex manner; BLA priming enhanced DG-LTP, and both NE and CORT mediated this effect. Furthermore, we found that ipsilateral BLA spaced activation (2 hr before PP tetanization) suppressed DG-LTP and that this suppressive effect was also mediated by NE and CORT. Priming the contralateral BLA enhanced DG-LTP similarly to the ipsilateral enhancement, but neither NE nor CORT mediated this effect. The spaced activation of the contralateral BLA did not suppress DG-LTP. Taken together, these results suggest that differential mechanisms underlie the ipsilateral and contralateral BLA effects on hippocampal plasticity. Hence, the BLA modulates hippocampal memory processes, presumably via the mediation of the stress hormones NE and CORT, to establish a diverse memory of the experience. Possibly, at the onset of an emotional event the stress hormones permissively mediate plasticity. However, their prolonged presence in the system may suppress the cognitive response to stress.
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Munro CA, Walling SG, Evans JH, Harley CW. Beta-adrenergic blockade in the dentate gyrus in vivo prevents high frequency-induced long-term potentiation of EPSP slope, but not long-term potentiation of population spike amplitude. Hippocampus 2002; 11:322-8. [PMID: 11769313 DOI: 10.1002/hipo.1046] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
High frequency (HF)-induced and norepinephrine (NE)-induced long-term potentiation have been hypothesized to utilize common mechanisms of induction and expression in the dentate gyrus. In vitro data tend to support this hypothesis, but few studies have been done in vivo. The present study records perforant path-evoked potentials simultaneously on two micropipettes, one filled with saline and the other with the beta-antagonist, timolol. Stimulation of the paragigantocellularis nucleus (PGi) was used as a method of producing NE release in the dentate gyrus, and thus, to assess the efficacy of beta-receptor blockade on the timolol pipette. Beta-blockade by timolol attenuated PGi-induced spike potentiation. HF-induced potentiation of the excitatory post-synaptic potential (EPSP) slope was also blocked by timolol, but HF-induced spike amplitude potentiation was unaffected. These results are consistent with an earlier report examining HF-long-term potentiation (LTP) following 6-OHDA-induced NE depletion, which showed that the EPSP slope LTP depended, for its full expression, on NE, but potentiation of the population spike amplitude component of HF-induced LTP did not. In the present study, PGi-induced potentiation of spike amplitude on the saline pipette was normal after HF-induced saturation of spike amplitude potentiation, suggesting that the mechanisms for expression of spike potentiation, as well as induction of spike potentiation, are separate for HF and NE stimulation.
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Affiliation(s)
- C A Munro
- Department of Psychology, Memorial University of Newfoundland, St. John's, Canada
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Swanson-Park JL, Coussens CM, Mason-Parker SE, Raymond CR, Hargreaves EL, Dragunow M, Cohen AS, Abraham WC. A double dissociation within the hippocampus of dopamine D1/D5 receptor and beta-adrenergic receptor contributions to the persistence of long-term potentiation. Neuroscience 1999; 92:485-97. [PMID: 10408599 DOI: 10.1016/s0306-4522(99)00010-x] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We compared the effects of the D1/D5 receptor antagonist SCH-23390 with the beta-adrenergic receptor antagonist propranolol on the persistence of long-term potentiation in the CA1 and dentate gyrus subregions of the hippocampus. In slices, SCH-23390 but not propranolol reduced the persistence of long-term potentiation in area CA1 without affecting its induction. The drugs exerted reverse effects in the dentate gyrus, although in this case the induction of long-term potentiation was also affected by propranolol. The lack of effect of SCH-23390 on the induction and maintenance of long-term potentiation in the dentate gyrus was confirmed in awake animals. The drug also had little or no effect on the expression of inducible transcription factors. In area CA1 of awake animals, SCH-23390 blocked persistence of long-term potentiation beyond 3 h, confirming the results in slices. To rule out a differential release of catecholamines induced by our stimulation protocols between brain areas, we compared the effects of the D1/D5 agonist SKF-38393 with the beta-adrenergic agonist isoproterenol on the persistence of a weakly induced, decremental long-term potentiation in CA1 slices. SKF-38393 but not isoproterenol promoted greater persistence of long-term potentiation over a 2-h period. In contrast, isoproterenol but not SKF-38392 facilitated the induction of long-term potentiation. These data demonstrate that there is a double dissociation of the catecholamine modulation of long-term potentiation between CA1 and the dentate gyrus, suggesting that long-term potentiation in these brain areas may be differentially consolidated according to the animal's behavioural state.
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Affiliation(s)
- J L Swanson-Park
- Department of Psychology and the Neuroscience Research Centre, University of Otago, Dunedin, New Zealand
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Abstract
Use-dependent alterations in synaptic efficacy are believed to form the basis for such complex brain functions as learning and memory and significantly contribute to the development of neuronal networks. The algorithm of synapse modification proposed by Hebb as early as 1949 is the coincident activation of pre- and postsynaptic neurons. The present review considers the evolution of experimental protocols in which postsynaptic cell depolarization through the recording microelectrode was used to reveal the manifestation of Hebb-type plasticity in the synaptic inputs of the neocortex and hippocampus. Special attention is focused on the inhibitory control of the Hebb-type plasticity. Disinhibition within the local neuronal circuits is considered to be an important factor in Hebbian plasticity, contributing to such phenomena as priming, primed burst potentiation, hippocampal theta-rhythm and cortical arousal. The role of various transmitters (acetylcholine, norepinephrine, gamma-amino-butyric acid) in disinhibition is discussed with a special emphasis on the brain noradrenergic system. Possible mechanisms of Hebbian synapse modification and their modulation by memory enhancing substances are considered. It is suggested that along with their involvement in disinhibition processes these substances may control Hebb-type plasticity through intracellular second messenger systems.
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Affiliation(s)
- V G Skrebitsky
- Brain Research Institute, Russian Academy of Medical Sciences, Moscow
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Cellular Mechanisms Of Long-Term Potentiation: Late Maintenance. NEURAL-NETWORK MODELS OF COGNITION - BIOBEHAVIORAL FOUNDATIONS 1997. [DOI: 10.1016/s0166-4115(97)80092-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Frizzell LM, Harley CW. The N-methyl-D-aspartate channel blocker ketamine does not attenuate, but enhances, locus coeruleus-induced potentiation in rat dentate gyrus. Brain Res 1994; 663:173-8. [PMID: 7531596 DOI: 10.1016/0006-8993(94)90476-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Norepinephrine (NE)-induced potentiation of the perforant path-evoked potential is blocked by N-methyl-D-aspartate (NMDA) receptor antagonism in vitro. Does this occur in vivo? A saline and a ketamine micropipette monitored perforant path-evoked potentials in the dentate gyrus of urethane-anesthetized rats. Activation of locus coeruleus (LC) produced short- and long-term potentiation of the perforant path-evoked potential on both pipettes. Spike amplitude potentiation was enhanced on the ketamine pipette. In contrast high frequency-induced potentiation on the ketamine pipette was attenuated. LC-NE potentiation may not require NMDA channel activation in vivo.
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Affiliation(s)
- L M Frizzell
- Psychology Department, Memorial University of Newfoundland, St. John's, Canada
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Wilson DA, Sullivan RM. Neurobiology of associative learning in the neonate: early olfactory learning. BEHAVIORAL AND NEURAL BIOLOGY 1994; 61:1-18. [PMID: 7907468 DOI: 10.1016/s0163-1047(05)80039-1] [Citation(s) in RCA: 177] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mammalian neonates have been simultaneously described as having particularly poor memory, as evidenced by infantile amnesia, and as being particularly excellent learners with unusually plastic nervous systems that are easily influenced by experience. An understanding of the neurobiological constraints and mechanisms of early learning may contribute to a unified explanation of these two disparate views. Toward that end, we review here our work on the neurobiology of learning and memory in neonates. Specifically, we have examined the neurobiology of early learning using an olfactory classical conditioning paradigm. Olfactory classical conditioning in neonates at the behavioral level conforms well with the requirements and outcomes of classical conditioning described in adults. Furthermore, specific neural correlates of this behavioral conditioning have been described including anatomical and physiological changes, neural pathways, and modulatory systems. In this Review, we outline the behavioral paradigm, the identified neural correlates, and apparent mechanisms of this learning. Finally, we compare the neurobiology of early learning with that reported for mature animals, with specific reference to the role of US-CS convergence, memory modulation, consolidation, and distributed memory.
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Affiliation(s)
- D A Wilson
- Department of Psychology, University of Oklahoma, Norman 73019
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Abstract
Use of learned odor cues by newborn rats is critical for pup survival. Rat pups acquire approach responses to maternal odors through an associative conditioning mechanism. This learned behavioral response is accompanied by a modification of olfactory bulb neural response patterns to the learned odor. Both the behavioral and neural response changes involved and require norepinephrine release in the olfactory bulb. The source of this norepinephrine is the locus coeruleus. It is proposed that the unique response properties of the locus coeruleus during the early postnatal period in the rat may facilitate acquisition of these critical early memories.
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Affiliation(s)
- R M Sullivan
- Department of Zoology, University of Oklahoma, Norman 73019
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Robinson GB, Fluharty SJ, Zigmond MJ, Sclabassi RJ, Berger TW. Recovery of hippocampal dentate granule cell responsiveness to entorhinal cortical input following norepinephrine depletion. Brain Res 1993; 614:21-8. [PMID: 7688646 DOI: 10.1016/0006-8993(93)91013-i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Hippocampal dentate granule cell responsivity to excitatory input from entorhinal perforant path fibers was examined in the chronic rabbit preparation following norepinephrine (NE) depletion induced with the neurotoxin DSP4. To examine granule cell responsivity as a function of perforant path activation, constant low frequency stimulation (0.1 Hz) was applied to the perforant path using an ascending intensity series. To examine granule cell responsivity to more complex patterns of stimulation, a train of impulses, with a random interstimulus interval (Poisson distribution; mean frequency of 2 Hz), was applied to the perforant path. Both single impulse and random interval impulse stimulation revealed that NE depletion increased the average amplitude of the perforant path-granule cell population spike. The random interval impulse stimulation revealed that NE depletion also increased the magnitude and duration of second order inhibitory interactions. These changes were transient, however, and recovered over the 21 day test period. Hippocampal NE levels were reduced an average of 80% between 23 and 38 days post-DSP4. The activity of the rate-limiting enzyme for NE synthesis, tyrosine hydroxylase (TH), was reduced an average of 60%. That NE levels were reduced to a greater extent than was TH activity is suggestive of increased NE synthesis within the remaining nerve terminals. Such an increase in NE synthesis may reflect a compensatory response underlying the functional recovery of electrophysiological responsiveness following partial NE depletion.
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Affiliation(s)
- G B Robinson
- Department of Psychology, University of New Brunswick, Fredericton, Canada
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Otani S, Ben-Ari Y. Biochemical correlates of long-term potentiation in hippocampal synapses. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1993; 35:1-41. [PMID: 8463060 DOI: 10.1016/s0074-7742(08)60567-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Figure 2 summarizes biochemical events which are currently known or hypothesized to participate in LTP induction/maintenance. Current evidence strongly suggests that postsynaptic Ca2+, both entered from the outside of cells and released from intracellular stores, is the initial key substance for the induction of LTP. A rise of [Ca2+]i triggers a variety of enzymatic reactions and initiates the enhancement of synaptic transmission. This first step may be achieved by direct/indirect phosphorylations of protein molecules in postsynaptic receptors/ion channels. This would result in an increase in receptor sensitivity. An immediate increase in the number of available postsynaptic receptors by modifications of spine morphology is another candidate. Such modifications may be accomplished by cytoskeleton rearrangements or changes in extracellular environments. A change in spine structure may also cause an increase in spine neck conductance. Although it is unknown to what extent the increase in [Ca2+]i affects cellular chemistry, Ca2+ probably also directly/indirectly stimulates cascades which exert effects more slowly. A delayed increase in metabotropic receptor sensitivity may occur. New synthesis of protein molecules may be involved in late periods of LTP by replacing turnovered molecules and/or by supplying new materials. Some of these chains of biochemical events may also apply to presynaptic terminals, although the existence of retrograde messenger substances must still be confirmed. In addition, interactions between different protein kinases and second messengers appear to occur to bring about final effects.
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Affiliation(s)
- S Otani
- INSERM Unité 29, Paris, France
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Sakai N, Sasa M, Ishihara K, Komure O, Tanaka C, Takaori S. Effects of L-threo-DOPS, a noradrenaline precursor, on the long-term potentiation in the rat hippocampal mossy fiber-CA3 region. Brain Res 1991; 567:267-73. [PMID: 1817730 DOI: 10.1016/0006-8993(91)90805-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS), a synthetic precursor of norepinephrine (NE), on the long-term potentiation (LTP) in the hippocampal mossy fiber-CA3 system was examined in urethane-anesthetized rats, the objective being to determine whether or not this drug acts as NE on the LTP. L-threo-DOPS may be effective for treating some type of mental disorders, including dementia. The LTP, induced in CA3 by tetanic stimulation (100 Hz for 1 s) applied to the mossy fiber persisted for more than 4 h. When L-threo-DOPS (50 and 150 micrograms) was injected into the lateral ventricle 30 min prior to the tetanic stimulation, there were no significant alterations in the LTP. However, in animals treated with reserpine (5 mg/kg i.p.) 24 h before the experiment, LTP was not induced with tetanic stimulation alone yet was obtained when tetanic stimulation was preceded by L-threo-DOPS (50 and 150 micrograms) applied to the ventricle. The LTP obtained by L-threo-DOPS in the reserpine-treated animal was inhibited by pretreatment with benserazide and was completely blocked by the simultaneous administration of sotalol. These results suggest that NE converted from L-threo-DOPS plays an important role in inducing LTP in the mossy fiber-CA3 system in the animals deficient in catecholamines.
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Affiliation(s)
- N Sakai
- Department of Pharmacology, Kobe University School of Medicine, Japan
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Harley C. Noradrenergic and locus coeruleus modulation of the perforant path-evoked potential in rat dentate gyrus supports a role for the locus coeruleus in attentional and memorial processes. PROGRESS IN BRAIN RESEARCH 1991; 88:307-21. [PMID: 1687619 DOI: 10.1016/s0079-6123(08)63818-2] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The perforant path-dentate gyrus synapse has provided a model system for functional neural plasticity in adult mammalian brain. NMDA-dependent long-term changes in neural connectivity occur at this synapse in response to high-frequency input. Norepinephrine (NE) applied exogenously or released endogenously can initiate both a short- and a long-term potentiation (LTP) of the dentate gyrus response to perforant path input. Triggering of the potentiated response depends on beta-receptor activation and does not require a high-frequency stimulus. An increase in locus coeruleus (LC) activity can initiate both short and LTP of the perforant path response, although a reduction in LC activity does not alter baseline perforant path responses. This chapter considers differences between NE modulation in vitro and in vivo, differences and similarities between NE-LTP and frequency-induced LTP, and the surprising specificity of NE effects at the perforant path synapse. Studies of NE in the dentate gyrus support a role for the LC in promoting both short- and long-term enhancement of responses to complex sensory inputs and are consistent with a role for the LC in memorial as well as attentional processes.
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Affiliation(s)
- C Harley
- Department of Psychology, Memorial University of Newfoundland, St. John's, Canada
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Frey U, Schroeder H, Matthies H. Dopaminergic antagonists prevent long-term maintenance of posttetanic LTP in the CA1 region of rat hippocampal slices. Brain Res 1990; 522:69-75. [PMID: 1977494 DOI: 10.1016/0006-8993(90)91578-5] [Citation(s) in RCA: 247] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The involvement of dopaminergic mechanisms in the induction and maintenance of posttetanic long-term potentiation (LTP) was investigated on CA1 cells of rat hippocampal slices. The presence of the dopamine receptor blocker domperidone in a concentration of 1 microM during tetanization with 3 trains of 100 impulses (100 Hz) and a train interval of 10 min influences neither the synaptic transmission nor the induction of LTP. However, the potentiation of both the population spike and the population EPSP gradually decreases, thus significantly differing from control LTP about 4 h after initiation and reaching the level of non-tetanized controls about 7-8 h after tetanization. The simultaneous presence of 1 microM apomorphine during tetanization abolishes this effect of domperidone indicating the specific dopaminolytic nature of its action. Also the presence of the dopamine antagonists sulpiride and flupenthixol, respectively, in a concentration of 1 microM during tetanization likewise prevents the occurrence of the late LTP maintenance. The determination of [14C]dopamine in 2 min fractions from the superfused slices after preloading during a preincubation period revealed that a low frequency stimulation of the Schaffer collaterals with 0.33 Hz does not influence the spontaneous efflux of dopamine, whereas the tetanization with an impulse train of 100 Hz produces a significantly enhanced release. The observations suggest that dopaminergic influences during and immediately after tetanization at least additionally contribute to the induction of postsynaptic mechanisms subserving a late, long-lasting maintenance of potentiation. The results also support the assumed existence of different subsequent stages of LTP.
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Affiliation(s)
- U Frey
- Institute of Neurobiology and Brain Research, Academy of Sciences, Magdeburg, G.D.R
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Abstract
The possible influence of the sleep-waking cycle on evoked neurotransmission and on the induction of long-term potentiation (LTP) and depression (LTD) was studied in the perforant path-granule cell system. Freely moving rats received a high-frequency stimulus train (8 bursts at 400 Hz) during slow-wave sleep (SWS), rapid eye movement (REM) sleep, and a still-alert (SAL) behavioral state. Trains applied during SAL and REM reliably elicited LTP of the excitatory postsynaptic potential (EPSP) slope, population spike height, and spike onset latency. Granule cell excitability was also enhanced, as indicated by a leftward shift of the EPSP-population spike (E-S) relation. In contrast, tetanization in SWS rarely produced 'classical' LTP and often failed to elicit any lasting change in field potentials. Furthermore, the following types of E-S change occurred almost exclusively after tetanization in SWS: (1) LTP of the EPSP accompanied by depression of the population spike, and (2) E-S potentiation without a change in EPSP. When LTP occurred, however, its magnitude was independent of the animal's behavioral state at the time of the train. In agreement with previous reports, the efficacy of low-frequency neurotransmission varied with behavioral state. A modulation index (MI) was introduced to quantify the difference between field potentials evoked in SAL and SWS. Interestingly, both the occurrence and magnitude of LTP were related to the strength of the MI, as determined in each rat before the train. After trains, the state-dependent modulation of transmission was maintained and was superimposed on LTP and LTD. The results suggest that synaptic plasticity is dynamically modulated during the sleep-wakefulness cycle.
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Affiliation(s)
- C R Bramham
- Department of Physiology, University of Bergen, Norway
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20
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Buzsáki G, Gage FH. Absence of long-term potentiation in the subcortically deafferented dentate gyrus. Brain Res 1989; 484:94-101. [PMID: 2713705 DOI: 10.1016/0006-8993(89)90351-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
All subcortical afferents to the dorsal hippocampus, running in the fimbria-fornix and supracallosal path, were removed by aspiration. Three to 5 months later the rats were implanted with chronic recording electrodes in the dentate gyrus and CA1 region, and stimulating electrodes in the angular bundle. In non-lesioned rats, high-frequency trains delivered to the angular bundle gave rise to a sustained increase of the evoked population spike in the dentate gyrus. In lesioned animals, high-frequency stimulation resulted in only short-lasting changes, and by 15 min after the conditioning trains the amplitude of both the population spike and field postsynaptic potentials returned to baseline. In lesioned rats large amplitude interictal spikes (less than 40 ms, 3-8 mV) occurred spontaneously. These findings suggest that either (1) coactivation of entorhinal and subcortical inputs is essential for the induction of long-lasting plastic changes in the dentate gyrus, or (2) the long-term potentiation mechanism is saturated by the chronically occurring interictal discharges in the subcortically denervated dentate gyrus.
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Affiliation(s)
- G Buzsáki
- Department of Neurosciences, University of California at San Diego, La Jolla 92093
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21
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Abstract
Long-term potentiation (LTP) and kindling are strikingly similar in many respects. Both are believed to model CNS plasticity, both are induced by the localized application of brief, high-frequency trains of electrical pulses through implanted electrodes, and both result in a lasting increase in the response to a constant stimulus. In addition to these formal similarities, recent findings have indicated that the two models may share aspects of an underlying neural mechanism, and this has led to the suggestion that LTP may constitute the cellular mechanism of kindling. However, other findings have indicated two models. This article discusses the differences in mechanisms and the relations between LTP and kindling.
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22
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Affiliation(s)
- H Matthies
- Institute of Neurobiology and Brain Research, Academy of Sciences of G.D.R., Magdeburg
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23
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Abstract
The present study characterized the effect of the formamidine pesticide, amitraz, upon hippocampal function in male Long-Evans rats. Animals were chronically prepared with a stimulating electrode in the perforant path and field potentials were recorded from a bipolar electrode situated across the granule cell layer of the dentate gyrus. Input/output functions and paired pulse inhibition were monitored in unrestrained, unanesthetized animals over a number of days following acute administration of 100 mg/kg of amitraz. Input/output functions revealed a decrease in excitatory postsynaptic potential (ESP) slope and an increase in population spike height 4 and 24 hr after treatment, with return to baseline by 48 hr. Tests of inhibition using pairs of stimulus pulses delivered at intervals ranging between 20 and 100 msec revealed a decrease in inhibition following amitraz. Both of these effects could be mimicked by administration of 0.1 mg/kg of the alpha-2 agonist clonidine, supporting this mode of action of amitraz on CNS function. These results indicate that systemic amitraz treatment produced a transient enhancement of excitatory and reduction of inhibitory processes in a CNS pathway.
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Affiliation(s)
- M E Gilbert
- Northrop Services Inc., Research Triangle Park, NC 27709
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24
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Leonard BJ, McNaughton BL, Barnes CA. Suppression of hippocampal synaptic plasticity during slow-wave sleep. Brain Res 1987; 425:174-7. [PMID: 3427418 DOI: 10.1016/0006-8993(87)90496-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The influence of behavioral state on the induction of long-term enhancement (LTE) of hippocampal synapses was studied in chronically prepared animals. Perforant path evoked field potentials and EEG were recorded from fascia dentata during slow-wave sleep (SWS) and waking. LTE was strongly suppressed during SWS, suggesting that hippocampal information storage may be inactivated at certain phases of the sleep cycle. Normal LTE was observed in the same animals while awake.
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Affiliation(s)
- B J Leonard
- Department of Psychology, University of Colorado, Boulder 80309
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25
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Stanton PK, Sarvey JM. Norepinephrine regulates long-term potentiation of both the population spike and dendritic EPSP in hippocampal dentate gyrus. Brain Res Bull 1987; 18:115-9. [PMID: 3030508 DOI: 10.1016/0361-9230(87)90039-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Hippocampal slices from norepinephrine (NE)-depleted rats exhibited marked reductions in long-term potentiation (LTP) of both the population spike and dendritic EPSP in the dentate gyrus. In contrast, depletion of serotonin (5-hydroxytryptamine, 5-HT) had no effect on either population spike or EPSP-LTP. In addition, superfusion of slices with NE produced potentiation of both the granule cell population spike and dendritic EPSP which persisted long after NE washout. These data support a role for NE in regulating long-term plasticity of both granule cell action potential firing and dendritic EPSPs.
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26
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Austin KB, Bronzino J, Morgane PJ. Prenatal protein malnutrition affects synaptic potentiation in the dentate gyrus of rats in adulthood. Brain Res 1986; 394:267-73. [PMID: 3021287 DOI: 10.1016/0165-3806(86)90102-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Long-term potentiation (LTP) was studied in the dentate gyrus of anesthetized normal and prenatally protein malnourished rats in adulthood. LTP was initiated by high-frequency stimulation of the perforant path. Potentiation of both population excitatory postsynaptic potential (EPSP) slope and population spike was studied at various times after conditioning out to 5 h. The results indicate that prenatal protein malnutrition has a differential effect on LTP. Although potentiation of the population spike was relatively unaffected, prenatal protein malnutrition did lead to a significant reduction in potentiation of the population EPSP. Several possibilities are proposed as to the cause of the differential effect.
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27
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Robinson GB, Racine RJ. Interactions between septal and entorhinal inputs to the rat dentate gyrus: facilitation effects. Brain Res 1986; 379:63-7. [PMID: 3017509 DOI: 10.1016/0006-8993(86)90255-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We examined facilitation effects between the medial septum and perforant path inputs to the dentate gyrus for the four possible combinations of paired-pulse activation. Facilitation effects occurred in all cases. The largest facilitation effects occurred when the septal pulse served as the conditioning pulse for the population spike subsequently evoked by a perforant path pulse. Using 3 pulses, we also examined the influence of septal activation on paired-pulse facilitation of the perforant path-granule cell population spike. A septal stimulation pulse, applied 6-10 ms prior to the onset of the population spike evoked by a perforant path conditioning pulse, did not affect the perforant path-dentate test response at any interpulse interval. If the septal pulse occurred immediately prior to population spike onset, however, there was a significantly greater depression of the test response from 70-3000 ms, but no effect at early intervals (20-50 ms). The effect of the septal pulse appears more consistent with a direct action of the septal terminals on granule cells than with an indirect action via the recurrent inhibitory interneurons.
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28
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Lynch MA, Bliss TV. Noradrenaline modulates the release of [14C]glutamate from dentate but not from CA1/CA3 slices of rat hippocampus. Neuropharmacology 1986; 25:493-8. [PMID: 2874519 DOI: 10.1016/0028-3908(86)90173-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The modulation of the release of [14C]glutamate by noradrenaline (NA) was investigated in slices prepared from the dentate gyrus and from the CA1/CA3 area of the hippocampus. In dentate, but not in CA1/CA3 slices, NA significantly enhanced K+-induced Ca2+-dependent release, and this effect was mimicked by clonidine and isoprenaline, but not by phenylephrine. The enhancement of release by NA was antagonised by propranolol, but not by yohimbine or phentolamine. These results suggest that NA does not modulate the release of glutamate in CA1/CA3, but does so in the dentate gyrus, probably by acting on presynaptically-located beta receptors.
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29
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Collingridge GL. Long term potentiation in the hippocampus: mechanisms of initiation and modulation by neurotransmitters. Trends Pharmacol Sci 1985. [DOI: 10.1016/0165-6147(85)90192-0] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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