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Khodaie B, Edelmann E, Leßmann V. Distinct GABAergic modulation of timing-dependent LTP in CA1 pyramidal neurons along the longitudinal axis of the mouse hippocampus. iScience 2024; 27:109320. [PMID: 38487018 PMCID: PMC10937841 DOI: 10.1016/j.isci.2024.109320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 01/25/2024] [Accepted: 02/20/2024] [Indexed: 03/17/2024] Open
Abstract
Synaptic plasticity in the hippocampus underlies episodic memory formation, with dorsal hippocampus being instrumental for spatial memory whereas ventral hippocampus is crucial for emotional learning. Here, we studied how GABAergic inhibition regulates physiologically relevant low repeat spike timing-dependent LTP (t-LTP) at Schaffer collateral-CA1 synapses along the dorsoventral hippocampal axis. We used two t-LTP protocols relying on only 6 repeats of paired spike-firing in pre- and postsynaptic cells within 10 s that differ in postsynaptic firing patterns. GABAA receptor mechanisms played a greater role in blocking 6× 1:1 t-LTP that recruits single postsynaptic action potentials. 6× 1:4 t-LTP that depends on postsynaptic burst-firing unexpectedly required intact GABAB receptor signaling. The magnitude of both t-LTP-forms decreased along the dorsoventral axis, despite increasing excitability and basal synaptic strength in this direction. This suggests that GABAergic inhibition contributes to the distinct roles of dorsal and ventral hippocampus in memory formation.
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Affiliation(s)
- Babak Khodaie
- Institut für Physiologie, Otto-von-Guericke-Universität (OVGU), Medizinische Fakultät, 39120 Magdeburg, Germany
- OVGU International ESF-funded Graduate School ABINEP, 39104 Magdeburg, Germany
| | - Elke Edelmann
- Institut für Physiologie, Otto-von-Guericke-Universität (OVGU), Medizinische Fakultät, 39120 Magdeburg, Germany
- Center for Behavioral Brain Sciences, 39104 Magdeburg, Germany
- OVGU International ESF-funded Graduate School ABINEP, 39104 Magdeburg, Germany
| | - Volkmar Leßmann
- Institut für Physiologie, Otto-von-Guericke-Universität (OVGU), Medizinische Fakultät, 39120 Magdeburg, Germany
- Center for Behavioral Brain Sciences, 39104 Magdeburg, Germany
- OVGU International ESF-funded Graduate School ABINEP, 39104 Magdeburg, Germany
- DZPG (German Center of Mental Health), partner site Halle/Jena/Magdeburg (CIRC), Magdeburg, Germany
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Leontiadis LJ, Trompoukis G, Felemegkas P, Tsotsokou G, Miliou A, Papatheodoropoulos C. Increased Inhibition May Contribute to Maintaining Normal Network Function in the Ventral Hippocampus of a Fmr1-Targeted Transgenic Rat Model of Fragile X Syndrome. Brain Sci 2023; 13:1598. [PMID: 38002556 PMCID: PMC10669536 DOI: 10.3390/brainsci13111598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
A common neurobiological mechanism in several neurodevelopmental disorders, including fragile X syndrome (FXS), is alterations in the balance between excitation and inhibition in the brain. It is thought that in the hippocampus, as in other brain regions, FXS is associated with increased excitability and reduced inhibition. However, it is still not known whether these changes apply to both the dorsal and ventral hippocampus, which appear to be differently involved in neurodegenerative disorders. Using a Fmr1 knock-out (KO) rat model of FXS, we found increased neuronal excitability in both the dorsal and ventral KO hippocampus and increased excitatory synaptic transmission in the dorsal hippocampus. Interestingly, synaptic inhibition is significantly increased in the ventral but not the dorsal KO hippocampus. Furthermore, the ventral KO hippocampus displays increased expression of the α1GABAA receptor subtype and a remarkably reduced rate of epileptiform discharges induced by magnesium-free medium. In contrast, the dorsal KO hippocampus displays an increased rate of epileptiform discharges and similar expression of α1GABAA receptors compared with the dorsal WT hippocampus. Blockade of α5GABAA receptors by L-655,708 did not affect epileptiform discharges in any genotype or hippocampal segment, and the expression of α5GABAA receptors did not differ between WT and KO hippocampus. These results suggest that the increased excitability of the dorsal KO hippocampus contributes to its heightened tendency to epileptiform discharges, while the increased phasic inhibition in the Fmr1-KO ventral hippocampus may represent a homeostatic mechanism that compensates for the increased excitability reducing its vulnerability to epileptic activity.
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Affiliation(s)
| | | | | | | | | | - Costas Papatheodoropoulos
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, 26504 Rion, Greece; (L.J.L.); (G.T. (George Trompoukis)); (P.F.); (G.T. (Giota Tsotsokou)); (A.M.)
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3
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Valero-Aracama MJ, Zheng F, Alzheimer C. Dorsal-Ventral Gradient of Activin Regulates Strength of GABAergic Inhibition along Longitudinal Axis of Mouse Hippocampus in an Activity-Dependent Fashion. Int J Mol Sci 2023; 24:13145. [PMID: 37685952 PMCID: PMC10487617 DOI: 10.3390/ijms241713145] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 08/20/2023] [Accepted: 08/22/2023] [Indexed: 09/10/2023] Open
Abstract
The functional and neurophysiological distinction between the dorsal and ventral hippocampus affects also GABAergic inhibition. In line with this notion, ventral CA1 pyramidal cells displayed a more dynamic and effective response to inhibitory input compared to their dorsal counterparts. We posit that this difference is effected by the dorsal-ventral gradient of activin A, a member of the transforming growth factor-β family, which is increasingly recognized for its modulatory role in brain regions involved in cognitive functions and affective behavior. Lending credence to this hypothesis, we found that in slices from transgenic mice expressing a dominant-negative mutant of activin receptor IB (dnActRIB), inhibitory transmission was enhanced only in CA1 neurons of the dorsal hippocampus, where the basal activin A level is much higher than in the ventral hippocampus. We next asked how a rise in endogenous activin A would affect GABAergic inhibition along the longitudinal axis of the hippocampus. We performed ex vivo recordings in wild-type and dnActRIB mice after overnight exposure to an enriched environment (EE), which engenders a robust increase in activin A levels in both dorsal and ventral hippocampi. Compared to control mice from standard cages, the behaviorally induced surge in activin A produced a decline in ventral inhibition, an effect that was absent in slices from dnActRIB mice. Underscoring the essential role of activin in the EE-associated modulation of ventral inhibition, this effect was mimicked by acute application of recombinant activin A in control slices. In summary, both genetic and behavioral manipulations of activin receptor signaling affected the dorsal-ventral difference in synaptic inhibition, suggesting that activin A regulates the strength of GABAergic inhibition in a region-specific fashion.
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4
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Anvari S, Foolad F, Javan M, Mirnajafi-Zadeh J, Fathollahi Y. A distinct impact of repeated morphine exposure on synaptic plasticity at Schaffer collateral-CA1, temporoammonic-CA1, and perforant pathway-dentate gyrus synapses along the longitudinal axis of the hippocampus. Hippocampus 2023; 33:47-62. [PMID: 36514833 DOI: 10.1002/hipo.23488] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 11/23/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022]
Abstract
We aimed to study how morphine affects synaptic transmission in the dentate gyrus and CA1 regions along the hippocampal long axis. For this, recording and measuring of field excitatory postsynaptic potentials (fEPSPs) were utilized to test the effects of repeated morphine exposure on paired-pulse evoked responses and long-term potentiation (LTP) at Schaffer collateral-CA1 (Sch-CA1), temporoammonic-CA1 (TA-CA1) and perforant pathway-dentate gyrus (PP-DG) synapses in transverse slices from the dorsal (DH), intermediate (IH), and ventral (VH) hippocampus in adult male rats. After repeated morphine exposure, the expression of opioid receptors and the α1 and α5 GABAA subunits were also examined. We found that repeated morphine exposure blunt the difference between the DH and the VH in their basal levels of synaptic transmission at Sch-CA1 synapses that were seen in the control groups. Significant paired-pulse facilitation of excitatory synaptic transmission was observed at Sch-CA1 synapses in slices taken from all three hippocampal segments as well as at PP-DG synapses in slices taken from the VH segment in the morphine-treated groups as compared to the control groups. Interestingly, significant paired-pulse inhibition of excitatory synaptic transmission was observed at TA-CA1 synapses in the DH slices from the morphine-treated group as compared to the control group. While primed-burst stimulation (a protocol reflecting normal neuronal firing) induced a robust LTP in hippocampal subfields in all control groups, resulting in a decaying LTP at TA-CA1 synapses in the VH slices and at PP-DG synapses in both the IH and VH slices taken from the morphine-treated rats. In the DH of morphine-treated rats, we found increased levels of the mRNAs encoding the α1 and α5 GABAA subunits as compared to the control group. Taken together, these findings suggest the potential mechanisms through which repeated morphine exposure causes differential changes in circuit excitability and synaptic plasticity in the dentate gyrus and CA1 regions along the hippocampal long axis.
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Affiliation(s)
- Sohrab Anvari
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Forough Foolad
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mohammad Javan
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Javad Mirnajafi-Zadeh
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Yaghoub Fathollahi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
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A. Samara M, Oikonomou GD, Trompoukis G, Madarou G, Adamopoulou M, Papatheodoropoulos C. Septotemporal variation in modulation of synaptic transmission, paired-pulse ratio and frequency facilitation/depression by adenosine and GABA B receptors in the rat hippocampus. Brain Neurosci Adv 2022; 6:23982128221106315. [PMID: 35782711 PMCID: PMC9240614 DOI: 10.1177/23982128221106315] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 05/19/2022] [Indexed: 11/26/2022] Open
Abstract
Short-term synaptic plasticity represents a fundamental mechanism in
neural information processing and is regulated by neuromodulators.
Here, using field recordings from the CA1 region of adult rat
hippocampal slices, we show that excitatory synaptic transmission is
suppressed by strong but not moderate activation of adenosine
A1 receptors by
2-Chloro-N6-cyclopentyladenosine (CCPA) more in the dorsal
than the ventral hippocampus; in contrast, both mild and strong
activation of GABAB receptors by baclofen (1 μM, 10 μM)
suppress synaptic transmission more in the ventral than the dorsal
hippocampus. Using a 10-pulse stimulation train of variable frequency,
we found that CCPA modulates short-term synaptic plasticity
independently of the suppression of synaptic transmission in both
segments of the hippocampus and at stimulation frequencies greater
than 10 Hz. However, specifically regarding the paired-pulse ratio
(PPR) and frequency facilitation/depression (FF/D) we found
significant drug action before but not after adjusting conditioning
responses to control levels. Activation of GABABRs by
baclofen suppressed synaptic transmission more in the ventral than the
dorsal hippocampus. Furthermore, relatively high (10 μM) but not low
(1 μM) baclofen concentration enhanced both PPR and FF in both
hippocampal segments at stimulation frequencies greater than 1 Hz,
independently of the suppression of synaptic transmission by baclofen.
These results show that A1Rs and GABABRs control
synaptic transmission more effectively in the dorsal and the ventral
hippocampus, respectively, and suggest that these receptors modulate
PPR and FF/D at different frequency bands of afferent input, in both
segments of the hippocampus.
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Affiliation(s)
- Maria A. Samara
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, Rion, Greece
| | - George D. Oikonomou
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, Rion, Greece
| | - George Trompoukis
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, Rion, Greece
| | - Georgia Madarou
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, Rion, Greece
| | - Maria Adamopoulou
- Laboratory of Neurophysiology, Department of Medicine, University of Patras, Rion, Greece
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6
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Lamotrigine Attenuates Neuronal Excitability, Depresses GABA Synaptic Inhibition, and Modulates Theta Rhythms in Rat Hippocampus. Int J Mol Sci 2021; 22:ijms222413604. [PMID: 34948401 PMCID: PMC8705017 DOI: 10.3390/ijms222413604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/29/2021] [Accepted: 12/05/2021] [Indexed: 12/03/2022] Open
Abstract
Theta oscillations generated in hippocampal (HPC) and cortical neuronal networks are involved in various aspects of brain function, including sensorimotor integration, movement planning, memory formation and attention. Disruptions of theta rhythms are present in individuals with brain disorders, including epilepsy and Alzheimer’s disease. Theta rhythm generation involves a specific interplay between cellular (ion channel) and network (synaptic) mechanisms. HCN channels are theta modulators, and several medications are known to enhance their activity. We investigated how different doses of lamotrigine (LTG), an HCN channel modulator, and antiepileptic and neuroprotective agent, would affect HPC theta rhythms in acute HPC slices (in vitro) and anaesthetized rats (in vivo). Whole-cell patch clamp recordings revealed that LTG decreased GABAA-fast transmission in CA3 cells, in vitro. In addition, LTG directly depressed CA3 and CA1 pyramidal neuron excitability. These effects were partially blocked by ZD 7288, a selective HCN blocker, and are consistent with decreased excitability associated with antiepileptic actions. Lamotrigine depressed HPC theta oscillations in vitro, also consistent with its neuronal depressant effects. In contrast, it exerted an opposite, enhancing effect, on theta recorded in vivo. The contradictory in vivo and in vitro results indicate that LTG increases ascending theta activating medial septum/entorhinal synaptic inputs that over-power the depressant effects seen in HPC neurons. These results provide new insights into LTG actions and indicate an opportunity to develop more precise therapeutics for the treatment of dementias, memory disorders and epilepsy.
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Sun Q, Jiang YQ, Lu MC. Topographic heterogeneity of intrinsic excitability in mouse hippocampal CA3 pyramidal neurons. J Neurophysiol 2020; 124:1270-1284. [PMID: 32937083 DOI: 10.1152/jn.00147.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Area CA3 in the hippocampus is traditionally thought to act as a homogeneous neural circuit that is vital for spatial navigation and episodic memories. However, recent studies have revealed that CA3 pyramidal neurons in dorsal hippocampus display marked anatomic and functional heterogeneity along the proximodistal (transverse) axis. The hippocampus is also known to be functionally segregated along the dorsoventral (longitudinal) axis, with dorsal hippocampus strongly involved in spatial navigation and ventral hippocampus associated with emotion and anxiety. Surprisingly, however, relatively little is known about CA3 functional heterogeneity along the dorsoventral axis. Here, we carried out mouse-brain-slice patch-clamp recordings and morphological analyses to examine the heterogeneity of CA3 cellular properties along both proximodistal and dorsoventral axes. We find that CA3 pyramidal neurons exhibit considerable heterogeneity of somatodendritic morphology and intrinsic membrane properties, with ventral CA3 (vCA3) displaying more elaborate somatodendritic morphology, lower intrinsic excitability, smaller input resistance, greater cell capacitance, and more prominent hyperpolarization-activated current than dorsal CA3 (dCA3). Furthermore, although both dCA3 and vCA3 exhibit proximal-to-distal gradients in intrinsic properties and neuronal morphology, these proximal-to-distal gradients in vCA3 are more moderate than those in dCA3. Taken together, our results extend previous findings on the proximodistal heterogeneity of dCA3 function and uncover a complex, yet orderly, pattern of topographic organization of CA3 neuronal features that extends to multiple anatomic dimensions and may contribute to its in vivo functional diversity.NEW & NOTEWORTHY Area CA3 is a major hippocampal region that is classically thought to act as a homogeneous neural network vital for spatial navigation and episodic memories. Here, we report that CA3 pyramidal neurons exhibit marked heterogeneity of somatodendritic morphology and cellular electrical properties along both proximodistal and dorsoventral axes. These new results uncover a complex, yet orderly, pattern of topographic organization of CA3 neuronal features that may contribute to its in vivo functional diversity.
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Affiliation(s)
- Qian Sun
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Yu-Qiu Jiang
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Melissa C Lu
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio
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8
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Trompoukis G, Papatheodoropoulos C. Dorsal-Ventral Differences in Modulation of Synaptic Transmission in the Hippocampus. Front Synaptic Neurosci 2020; 12:24. [PMID: 32625076 PMCID: PMC7316154 DOI: 10.3389/fnsyn.2020.00024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/14/2020] [Indexed: 11/17/2022] Open
Abstract
Functional diversification along the longitudinal axis of the hippocampus is a rapidly growing concept. Modulation of synaptic transmission by neurotransmitter receptors may importantly contribute to specialization of local intrinsic network function along the hippocampus. In the present study, using transverse slices from the dorsal and the ventral hippocampus of adult rats and recordings of evoked field postsynaptic excitatory potentials (fEPSPs) from the CA1 stratum radiatum, we aimed to compare modulation of synaptic transmission between the dorsal and the ventral hippocampus. We found that transient heterosynaptic depression (tHSD, <2 s), a physiologically relevant phenomenon of regulation of excitatory synaptic transmission induced by paired stimulation of two independent inputs to stratum radiatum of CA1 field, has an increased magnitude and duration in the ventral hippocampus, presumably contributing to increased input segregation in this segment of the hippocampus. GABAB receptors, GABAA receptors, adenosine A1 receptors and L-type voltage-gated calcium channels appear to contribute differently to tHSD in the two hippocampal segments; GABABRs play a predominant role in the ventral hippocampus while both GABABRs and A1Rs play important roles in the dorsal hippocampus. Activation of GABAB receptors by an exogenous agonist, baclofen, robustly and reversibly modulated both the initial fast and the late slow components of excitatory synaptic transmission, expressed by the fEPSPslope and fEPSP decay time constant (fEPSPτ), respectively. Specifically, baclofen suppressed fEPSP slope more in the ventral than in the dorsal hippocampus and enhanced fEPSPτ more in the dorsal than in the ventral hippocampus. Also, baclofen enhanced paired-pulse facilitation in the two hippocampal segments similarly. Blockade of GABAB receptors did not affect basal paired-pulse facilitation in either hippocampal segment. We propose that the revealed dorsal-ventral differences in modulation of synaptic transmission may provide a means for specialization of information processing in the local neuronal circuits, thereby significantly contributing to diversifying neuronal network functioning along the dorsal-ventral axis of hippocampus.
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Affiliation(s)
- George Trompoukis
- Laboratory of Physiology, Department of Medicine, University of Patras, Patras, Greece
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Netsyk O, Hammoud H, Korol SV, Jin Z, Tafreshiha AS, Birnir B. Tonic
GABA
‐activated synaptic and extrasynaptic currents in dentate gyrus granule cells and
CA3
pyramidal neurons along the mouse hippocampal dorsoventral axis. Hippocampus 2020; 30:1146-1157. [DOI: 10.1002/hipo.23245] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 05/24/2020] [Accepted: 05/26/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Olga Netsyk
- Department of Medical Cell Biology Uppsala University Uppsala Sweden
| | - Hayma Hammoud
- Department of Medical Cell Biology Uppsala University Uppsala Sweden
| | - Sergiy V. Korol
- Department of Medical Cell Biology Uppsala University Uppsala Sweden
| | - Zhe Jin
- Department of Medical Cell Biology Uppsala University Uppsala Sweden
| | | | - Bryndis Birnir
- Department of Medical Cell Biology Uppsala University Uppsala Sweden
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Brown KA, Filipov NM, Wagner JJ. Dorsoventral-Specific Effects of Nerve Agent Surrogate Diisopropylfluorophosphate on Synaptic Transmission in the Mouse Hippocampus. J Pharmacol Exp Ther 2020; 373:10-23. [DOI: 10.1124/jpet.119.263053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 12/16/2019] [Indexed: 11/22/2022] Open
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β-adrenergic receptors reduce the threshold for induction and stabilization of LTP and enhance its magnitude via multiple mechanisms in the ventral but not the dorsal hippocampus. Neurobiol Learn Mem 2018; 151:71-84. [PMID: 29653257 DOI: 10.1016/j.nlm.2018.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 03/19/2018] [Accepted: 04/07/2018] [Indexed: 12/27/2022]
Abstract
The hippocampus is a functionally heterogeneous structure with the cognitive and emotional signal processing ascribed to the dorsal (DH) and the ventral hippocampus (VH) respectively. However, the underlying mechanisms are poorly understood. Noradrenaline is released in hippocampus during emotional arousal modulating synaptic plasticity and memory consolidation through activation of β adrenergic receptors (β-ARs). Using recordings of field excitatory postsynaptic potentials from the CA1 field of adult rat hippocampal slices we demonstrate that long-term potentiation (LTP) induced either by theta-burst stimulation (TBS) that mimics a physiological firing pattern of hippocampal neurons or by high-frequency stimulation is remarkably more sensitive to β-AR activation in VH than in DH. Thus, pairing of subthreshold primed burst stimulation with activation of β-ARs by their agonist isoproterenol (1 μM) resulted in a reliable induction of NMDA receptor-dependent LTP in the VH without affecting LTP in the DH. Activation of β-ARs by isoproterenol during application of intense TBS increased the magnitude of LTP in both hippocampal segments but facilitated voltage-gated calcium channel-dependent LTP in VH only. Endogenous β-AR activation contributed to the stabilization and the magnitude of LTP in VH but not DH as demonstrated by the effects of the β-ARs antagonist propranolol (10 μM). Exogenous (but not endogenous) β-AR activation strongly increased TBS-induced facilitation of postsynaptic excitability in VH. In DH, isoproterenol only produced a moderate and GABAergic inhibition-dependent enhancement in the facilitation of synaptic burst responses. Paired-pulse facilitation did not change with LTP at any experimental condition suggesting that expression of LTP does not involve presynaptic mechanisms. These findings suggest that β-AR may act as a switch that selectively promotes synaptic plasticity in VH through multiple ways and provide thus a first clue to mechanisms that underlie VH involvement in emotionality.
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12
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Immature Status Epilepticus: In Vitro Models Reveal Differences in Cholinergic Control and HFO Properties of Adult CA3 Interictal Discharges in Temporal vs Septal Hippocampus. Neuroscience 2018; 369:386-398. [DOI: 10.1016/j.neuroscience.2017.11.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 10/30/2017] [Accepted: 11/16/2017] [Indexed: 01/31/2023]
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13
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Cao B, Ni HY, Li J, Zhou Y, Bian XL, Tao Y, Cai CY, Qin C, Wu HY, Chang L, Luo CX, Zhu DY. (+)-Borneol suppresses conditioned fear recall and anxiety-like behaviors in mice. Biochem Biophys Res Commun 2017; 495:1588-1593. [PMID: 29223397 DOI: 10.1016/j.bbrc.2017.12.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 12/05/2017] [Indexed: 01/19/2023]
Abstract
Fear- and anxiety-related psychiatric disorders have been one of the major chronic diseases afflicting patients for decades, and new compounds for treating such disorders remain to be developed. (+)-Borneol, a bicyclic monoterpene found in several species of Artemisia and Dipterocarpaceae, is widely used for anxiety, pain and anesthesia in Chinese medicine. Meanwhile, it can potentiate GABA (γ-aminobutyric acid) activity directly in recombinant GABAA receptors. The present study was to investigate the effects of (+)-Borneol on both contextual and cued fear recall. Interestingly, microinjection of (+)-Borneol into the dorsal hippocampus inhibited 24 h and 7 d contextual fear, whereas its infusion into ventral hippocampus only reduced 24 h cued fear responses. Moreover, microinjection of (+)-Borneol into dorsal but not ventral hippocampus suppressed anxiety-like behaviors in the open field test, light/dark exploration and the elevated plus maze test. As selective GABAA receptor antagonist bicuculline reversed the effect of (+)-Borneol on contextual fear paradigm and the drug potentiated GABA-evoked currents in acute hippocampus slices, modulation of the GABAergic neurotransmission may explain the effects of (+)-Borneol. Our findings suggest that (+)-Borneol can serve as a new therapeutic in fear- and anxiety-related disorders.
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Affiliation(s)
- Bo Cao
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Huan-Yu Ni
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Jun Li
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Ying Zhou
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Xin-Lan Bian
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Yan Tao
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Cheng-Yun Cai
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Cheng Qin
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Hai-Yin Wu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Lei Chang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Chun-Xia Luo
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Dong-Ya Zhu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China; Key Laboratory of Precision Medicine of Cardiovascular Disease, Nanjing Medical University, Nanjing 211166, China; Institution of Stem Cells and Neuroregeneration, Nanjing Medical University, Nanjing 211166, China.
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14
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Almonte AG, Ewin SE, Mauterer MI, Morgan JW, Carter ES, Weiner JL. Enhanced ventral hippocampal synaptic transmission and impaired synaptic plasticity in a rodent model of alcohol addiction vulnerability. Sci Rep 2017; 7:12300. [PMID: 28951619 PMCID: PMC5615051 DOI: 10.1038/s41598-017-12531-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/12/2017] [Indexed: 02/06/2023] Open
Abstract
It has long been appreciated that adolescence represents a uniquely vulnerable period when chronic exposure to stressors can precipitate the onset of a broad spectrum of psychiatric disorders and addiction in adulthood. However, the neurobiological substrates and the full repertoire of adaptations within these substrates making adolescence a particularly susceptible developmental stage are not well understood. Prior work has demonstrated that a rodent model of adolescent social isolation (aSI) produces robust and persistent increases in phenotypes relevant to anxiety/stressor disorders and alcohol addiction, including anxiogenesis, deficits in fear extinction, and increased ethanol consumption. Here, we used extracellular field recordings in hippocampal slices to investigate adaptations in synaptic function and synaptic plasticity arising from aSI. We demonstrate that this early life stressor leads to enhanced excitatory synaptic transmission and decreased levels of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses. Further, these changes were largely confined to the ventral hippocampus. As the ventral hippocampus is integral to neurocircuitry that mediates emotional behaviors, our results add to mounting evidence that aSI has profound effects on brain areas that regulate affective states. These studies also lend additional support to our recent proposal of the aSI model as a valid model of alcohol addiction vulnerability.
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Affiliation(s)
- Antoine G Almonte
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
| | - Sarah E Ewin
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
| | - Madelyn I Mauterer
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
| | - James W Morgan
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
| | - Eugenia S Carter
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
| | - Jeffrey L Weiner
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA.
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15
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Dendritic GIRK Channels Gate the Integration Window, Plateau Potentials, and Induction of Synaptic Plasticity in Dorsal But Not Ventral CA1 Neurons. J Neurosci 2017; 37:3940-3955. [PMID: 28280255 DOI: 10.1523/jneurosci.2784-16.2017] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 02/28/2017] [Accepted: 03/04/2017] [Indexed: 01/05/2023] Open
Abstract
Studies comparing neuronal activity at the dorsal and ventral poles of the hippocampus have shown that the scale of spatial information increases and the precision with which space is represented declines from the dorsal to ventral end. These dorsoventral differences in neuronal output and spatial representation could arise due to differences in computations performed by dorsal and ventral CA1 neurons. In this study, we tested this hypothesis by quantifying the differences in dendritic integration and synaptic plasticity between dorsal and ventral CA1 pyramidal neurons of rat hippocampus. Using a combination of somatic and dendritic patch-clamp recordings, we show that the threshold for LTP induction is higher in dorsal CA1 neurons and that a G-protein-coupled inward-rectifying potassium channel mediated regulation of dendritic plateau potentials and dendritic excitability underlies this gating. By contrast, similar regulation of LTP is absent in ventral CA1 neurons. Additionally, we show that generation of plateau potentials and LTP induction in dorsal CA1 neurons depends on the coincident activation of Schaffer collateral and temporoammonic inputs at the distal apical dendrites. The ventral CA1 dendrites, however, can generate plateau potentials in response to temporally dispersed excitatory inputs. Overall, our results highlight the dorsoventral differences in dendritic computation that could account for the dorsoventral differences in spatial representation.SIGNIFICANCE STATEMENT The dorsal and ventral parts of the hippocampus encode spatial information at very different scales. Whereas the place-specific firing fields are small and precise at the dorsal end of the hippocampus, neurons at the ventral end have comparatively larger place fields. Here, we show that the dorsal CA1 neurons have a higher threshold for LTP induction and require coincident timing of excitatory synaptic inputs for the generation of dendritic plateau potentials. By contrast, ventral CA1 neurons can integrate temporally dispersed inputs and have a lower threshold for LTP. Together, these dorsoventral differences in the threshold for LTP induction could account for the differences in scale of spatial representation at the dorsal and ventral ends of the hippocampus.
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16
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Milior G, Di Castro MA, Sciarria LP, Garofalo S, Branchi I, Ragozzino D, Limatola C, Maggi L. Electrophysiological Properties of CA1 Pyramidal Neurons along the Longitudinal Axis of the Mouse Hippocampus. Sci Rep 2016; 6:38242. [PMID: 27922053 PMCID: PMC5138623 DOI: 10.1038/srep38242] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 11/07/2016] [Indexed: 12/18/2022] Open
Abstract
Evidence for different physiological properties along the hippocampal longitudinal axis is emerging. Here, we examined the electrophysiological features of neurons at different dorso-ventral sites of the mouse CA1 hippocampal region. Cell position was defined with respect to longitudinal coordinates of each slice. We measured variations in neuronal excitability, subthreshold membrane properties and neurotransmitter responses along the longitudinal axis. We found that (i) pyramidal cells of the dorsal hippocampus (DH) were less excitable than those of the ventral hippocampus (VH). Resting Membrane Potential (RMP) was more hyperpolarized and somatic Input Resistance (Ri) was lower in DH compared to VH. (ii) The Paired-pulse ratio (PPR) of focally induced synaptic responses was systematically reduced from the DH to the VH; (iii) Long-term-potentiation was most pronounced in the DH and fell gradually in the intermediate hippocampus and in the VH; (iv) the frequency of miniature GABAergic events was higher in the VH than in the DH; (v) the PPR of evoked inhibitory post-synaptic current (IPSC) was higher in the DH than in the VH. These findings indicate an increased probability of both GABA and glutamate release and a reduced plasticity in the ventral compared to more dorsal regions of the hippocampus.
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Affiliation(s)
- Giampaolo Milior
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy.,Inserm U1127, CNRS UMR7225, Sorbonne Universités, UPMC UMR S1127, Institut du Cerveau et de la Moelle épinière, Paris 75013, France
| | - Maria Amalia Di Castro
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
| | - Livio Pepe' Sciarria
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
| | - Stefano Garofalo
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
| | - Igor Branchi
- Section of Behavioural Neurosciences, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Davide Ragozzino
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy.,IRCCS Neuromed, Pozzilli, IS, Italy
| | - Cristina Limatola
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy.,IRCCS Neuromed, Pozzilli, IS, Italy
| | - Laura Maggi
- Pasteur Institute Rome-Department of Physiology and Pharmacology, Sapienza University of Rome, Italy
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17
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Malik R, Dougherty KA, Parikh K, Byrne C, Johnston D. Mapping the electrophysiological and morphological properties of CA1 pyramidal neurons along the longitudinal hippocampal axis. Hippocampus 2016; 26:341-61. [PMID: 26333017 PMCID: PMC4760884 DOI: 10.1002/hipo.22526] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2015] [Indexed: 01/10/2023]
Abstract
Differences in behavioral roles, anatomical connectivity, and gene expression patterns in the dorsal, intermediate, and ventral regions of the hippocampus are well characterized. Relatively fewer studies have, however, focused on comparing the physiological properties of neurons located at different dorsoventral extents of the hippocampus. Recently, we reported that dorsal CA1 neurons are less excitable than ventral neurons. There is little or no information for how neurons in the intermediate hippocampus compare to those from the dorsal and ventral ends. Also, it is not known whether the transition of properties along the dorsoventral axis is gradual or segmented. In this study, we developed a statistical model to predict the dorsoventral position of transverse hippocampal slices. Using current clamp recordings combined with this model, we found that CA1 neurons in dorsal, intermediate, and ventral hippocampus have distinct electrophysiological and morphological properties and that the transition in most (but not all) of these properties from the ventral to dorsal end is gradual. Using linear and segmented regression analyses, we found that input resistance and resting membrane potential changed linearly along the V-D axis. Interestingly, the transition in resonance frequency, rebound slope, dendritic branching in stratum radiatum, and action potential properties was segmented along the V-D axis. Together, the findings from this study highlight the heterogeneity in CA1 neuronal properties along the entire longitudinal axis of hippocampus.
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Affiliation(s)
- Ruchi Malik
- Center for Learning and Memory, University of Texas at Austin, Austin, Texas
| | - Kelly Ann Dougherty
- Center for Learning and Memory, University of Texas at Austin, Austin, Texas
- Department of Biology, Rhodes College, Memphis, Tennessee
| | - Komal Parikh
- Center for Learning and Memory, University of Texas at Austin, Austin, Texas
| | - Connor Byrne
- Center for Learning and Memory, University of Texas at Austin, Austin, Texas
| | - Daniel Johnston
- Center for Learning and Memory, University of Texas at Austin, Austin, Texas
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18
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Lasting Differential Effects on Plasticity Induced by Prenatal Stress in Dorsal and Ventral Hippocampus. Neural Plast 2016; 2016:2540462. [PMID: 26881096 PMCID: PMC4736977 DOI: 10.1155/2016/2540462] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/18/2015] [Accepted: 12/20/2015] [Indexed: 12/14/2022] Open
Abstract
Early life adversaries have a profound impact on the developing brain structure and functions that persist long after the original traumatic experience has vanished. One of the extensively studied brain structures in relation to early life stress has been the hippocampus because of its unique association with cognitive processes of the brain. While the entire hippocampus shares the same intrinsic organization, it assumes different functions in its dorsal and ventral sectors (DH and VH, resp.), based on different connectivity with other brain structures. In the present review, we summarize the differences between DH and VH and discuss functional and structural effects of prenatal stress in the two sectors, with the realization that much is yet to be explored in understanding the opposite reactivity of the DH and VH to stressful stimulation.
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19
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Kouvaros S, Papatheodoropoulos C. Major dorsoventral differences in the modulation of the local CA1 hippocampal network by NMDA, mGlu5, adenosine A2A and cannabinoid CB1 receptors. Neuroscience 2016; 317:47-64. [PMID: 26762803 DOI: 10.1016/j.neuroscience.2015.12.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 12/23/2015] [Accepted: 12/30/2015] [Indexed: 11/29/2022]
Abstract
Recent research points to diversification in the local neuronal circuitry between dorsal (DH) and ventral (VH) hippocampus that may be involved in the large-scale functional segregation along the long axis of the hippocampus. Here, using CA1 field recordings from rat hippocampal slices, we show that activation of N-methyl-d-aspartate receptors (NMDARs) reduced excitatory transmission more in VH than in DH, with an adenosine A1 receptor-independent mechanism, and reduced inhibition and enhanced postsynaptic excitability only in DH. Strikingly, co-activation of metabotropic glutamate receptor-5 (mGluR5) with NMDAR, by CHPG and NMDA respectively, strongly potentiated the effects of NMDAR in DH but had not any potentiating effect in VH. Furthermore, the synergistic actions in DH were occluded by blockade of adenosine A2A receptors (A2ARs) by their antagonist ZM 241385 demonstrating a tonic action of these receptors in DH. Exogenous activation of A2ARs by 4-[2-[[6-amino-9-(N-ethyl-β-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (CGS 21680) did not change the effects of mGluR5-NMDAR co-activation in either hippocampal pole. Importantly, blockade of cannabinoid CB1 receptors (CB1Rs) by their antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM 281) restricted the synergistic actions of mGluR5-NMDARs on excitatory synaptic transmission and postsynaptic excitability and abolished their effect on inhibition. Furthermore, AM 281 increased the excitatory transmission only in DH indicating that CB1Rs were tonically active in DH but not VH. Removing the magnesium ions from the perfusion medium neither stimulated the interaction between mGluR5 and NMDAR in VH nor augmented the synergy of the two receptors in DH. These findings show that the NMDAR-dependent modulation of fundamental parameters of the local neuronal network, by mGluR5, A2AR and CB1R, markedly differs between DH and VH. We propose that the higher modulatory role of A2AR and mGluR5, in combination with the role of CB1Rs, provide DH with higher functional flexibility of its NMDARs, compared with VH.
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Affiliation(s)
- S Kouvaros
- Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, 26504 Rion, Greece
| | - C Papatheodoropoulos
- Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, 26504 Rion, Greece.
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20
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Hernandez RV, Puro AC, Manos JC, Huitron-Resendiz S, Reyes KC, Liu K, Vo K, Roberts AJ, Gruol DL. Transgenic mice with increased astrocyte expression of IL-6 show altered effects of acute ethanol on synaptic function. Neuropharmacology 2015; 103:27-43. [PMID: 26707655 DOI: 10.1016/j.neuropharm.2015.12.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 11/21/2015] [Accepted: 12/14/2015] [Indexed: 11/29/2022]
Abstract
A growing body of evidence has revealed that resident cells of the central nervous system (CNS), and particularly the glial cells, comprise a neuroimmune system that serves a number of functions in the normal CNS and during adverse conditions. Cells of the neuroimmune system regulate CNS functions through the production of signaling factors, referred to as neuroimmune factors. Recent studies show that ethanol can activate cells of the neuroimmune system, resulting in the elevated production of neuroimmune factors, including the cytokine interleukin-6 (IL-6). Here we analyzed the consequences of this CNS action of ethanol using transgenic mice that express elevated levels of IL-6 through increased astrocyte expression (IL-6-tg) to model the increased IL-6 expression that occurs with ethanol use. Results show that increased IL-6 expression induces neuroadaptive changes that alter the effects of ethanol. In hippocampal slices from non-transgenic (non-tg) littermate control mice, synaptically evoked dendritic field excitatory postsynaptic potential (fEPSP) and somatic population spike (PS) at the Schaffer collateral to CA1 pyramidal neuron synapse were reduced by acute ethanol (20 or 60 mM). In contrast, acute ethanol enhanced the fEPSP and PS in hippocampal slices from IL-6 tg mice. Long-term synaptic plasticity of the fEPSP (i.e., LTP) showed the expected dose-dependent reduction by acute ethanol in non-tg hippocampal slices, whereas LTP in the IL-6 tg hippocampal slices was resistant to this depressive effect of acute ethanol. Consistent with altered effects of acute ethanol on synaptic function in the IL-6 tg mice, EEG recordings showed a higher level of CNS activity in the IL-6 tg mice than in the non-tg mice during the period of withdrawal from an acute high dose of ethanol. These results suggest a potential role for neuroadaptive effects of ethanol-induced astrocyte production of IL-6 as a mediator or modulator of the actions of ethanol on the CNS, including persistent changes in CNS function that contribute to cognitive dysfunction and the development of alcohol dependence.
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Affiliation(s)
- Ruben V Hernandez
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Alana C Puro
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jessica C Manos
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Salvador Huitron-Resendiz
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Kenneth C Reyes
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Kevin Liu
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Khanh Vo
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Amanda J Roberts
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Donna L Gruol
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA.
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21
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Papatheodoropoulos C. Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors. BMC Neurosci 2015; 16:75. [PMID: 26556486 PMCID: PMC4641374 DOI: 10.1186/s12868-015-0213-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/04/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Elucidating specializations of the intrinsic neuronal network between the dorsal and the ventral hippocampus is a recently emerging area of research that is expected to help us understand the mechanisms underlying large scale functional diversification along the hippocampus. The aim of this study was to characterize spontaneous network activity between the dorsal and the ventral hippocampus induced under conditions of partial or complete blockade of GABAergic inhibition (i.e. disinhibition). RESULTS Using field recordings from the CA3 and CA1 fields of hippocampal slices from adult rats I found that ventral compared with dorsal hippocampus slices displayed higher propensity for and higher frequency of occurrence of spontaneous field potentials (spfps) at every level of disinhibition. Also NMDA receptor-depended spfps (spfps(-nmda)) occurred with higher probability more frequently and were larger in the ventral compared with the dorsal hippocampus. Importantly, blockade of GABA(B) receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps(-nmda) in the dorsal compared with the ventral hippocampal slices and increased spfps(-nmda) only in dorsal slices. CONCLUSION These results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors. Furthermore, the GABA(B) receptors control the total and the NMDA receptor-dependent excitation much less effectively in the ventral part of the hippocampus. It is proposed that NMDA and GABA(B) receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.
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Affiliation(s)
- Costas Papatheodoropoulos
- Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, Rion, 26504, Patras, Greece.
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22
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Buzsáki G. Hippocampal sharp wave-ripple: A cognitive biomarker for episodic memory and planning. Hippocampus 2015; 25:1073-188. [PMID: 26135716 PMCID: PMC4648295 DOI: 10.1002/hipo.22488] [Citation(s) in RCA: 943] [Impact Index Per Article: 104.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 06/30/2015] [Indexed: 12/23/2022]
Abstract
Sharp wave ripples (SPW-Rs) represent the most synchronous population pattern in the mammalian brain. Their excitatory output affects a wide area of the cortex and several subcortical nuclei. SPW-Rs occur during "off-line" states of the brain, associated with consummatory behaviors and non-REM sleep, and are influenced by numerous neurotransmitters and neuromodulators. They arise from the excitatory recurrent system of the CA3 region and the SPW-induced excitation brings about a fast network oscillation (ripple) in CA1. The spike content of SPW-Rs is temporally and spatially coordinated by a consortium of interneurons to replay fragments of waking neuronal sequences in a compressed format. SPW-Rs assist in transferring this compressed hippocampal representation to distributed circuits to support memory consolidation; selective disruption of SPW-Rs interferes with memory. Recently acquired and pre-existing information are combined during SPW-R replay to influence decisions, plan actions and, potentially, allow for creative thoughts. In addition to the widely studied contribution to memory, SPW-Rs may also affect endocrine function via activation of hypothalamic circuits. Alteration of the physiological mechanisms supporting SPW-Rs leads to their pathological conversion, "p-ripples," which are a marker of epileptogenic tissue and can be observed in rodent models of schizophrenia and Alzheimer's Disease. Mechanisms for SPW-R genesis and function are discussed in this review.
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Affiliation(s)
- György Buzsáki
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, New York
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23
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Striking differences in synaptic facilitation along the dorsoventral axis of the hippocampus. Neuroscience 2015; 301:454-70. [DOI: 10.1016/j.neuroscience.2015.06.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 05/07/2015] [Accepted: 06/18/2015] [Indexed: 12/23/2022]
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24
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Differences in paired-pulse inhibition and facilitation in the dentate gyrus and CA3 field between dorsal and ventral rat hippocampus. Brain Res 2015; 1608:21-30. [PMID: 25770056 DOI: 10.1016/j.brainres.2015.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 02/10/2015] [Accepted: 03/02/2015] [Indexed: 12/28/2022]
Abstract
We studied the processes of inhibition and facilitation in the dentate gyrus (DG) and the CA3 field by examining the effects of paired-pulse stimulation on the evoked population spike (PS) in dorsal (DH) and ventral (VH) hippocampal slices from the adult rat. The antidromic-orthodromic (A-O) and the orthodromic-orthodromic (O-O) paired-pulse stimulation protocols were used at varying inter-pulse intervals (IPI). In the DG, the A-O stimulation produced an early depression of PS lasting 30-40ms which was significantly stronger in the VH compared with DH. The O-O stimulation produced a biphasic pattern of effects, in both dorsal and ventral DG, consisting of an early depression of PS followed by facilitation at relatively longer intervals. In the DH but not the VH the phase of facilitation was followed by a late depression of PS (>200ms). In the CA3 field both A-O and O-O stimulation had a biphasic effect consisting of an early phase of strong depression of similar strength in DH and VH. The depression was followed by a phase of facilitation which was more pronounced with O-O stimulation. The facilitation observed with the O-O stimulation was much stronger in DH than VH and in DH only it was significantly reduced by the antagonist of GABAB receptors CGP52432. Furthermore, the facilitation was insensitive to changes in [Ca(2+)]o in both hippocampal poles. These findings suggest that the dorsal compared with ventral DG is more amenable to fast-frequency input but filters out slow-frequency inputs more reliably while the gating and amplification of the excitatory input in the CA3 circuitry is more prominent in DH than in VH.
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25
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Kim CS, Johnston D. A1 adenosine receptor-mediated GIRK channels contribute to the resting conductance of CA1 neurons in the dorsal hippocampus. J Neurophysiol 2015; 113:2511-23. [PMID: 25652929 DOI: 10.1152/jn.00951.2014] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/01/2015] [Indexed: 01/06/2023] Open
Abstract
The dorsal and ventral hippocampi are functionally and anatomically distinct. Recently, we reported that dorsal Cornu Ammonis area 1 (CA1) neurons have a more hyperpolarized resting membrane potential and a lower input resistance and fire fewer action potentials for a given current injection than ventral CA1 neurons. Differences in the hyperpolarization-activated cyclic nucleotide-gated cation conductance between dorsal and ventral neurons have been reported, but these differences cannot fully account for the different resting properties of these neurons. Here, we show that coupling of A1 adenosine receptors (A1ARs) to G-protein-coupled inwardly rectifying potassium (GIRK) conductance contributes to the intrinsic membrane properties of dorsal CA1 neurons but not ventral CA1 neurons. The block of GIRKs with either barium or the more specific blocker Tertiapin-Q revealed that there is more resting GIRK conductance in dorsal CA1 neurons compared with ventral CA1 neurons. We found that the higher resting GIRK conductance in dorsal CA1 neurons was mediated by tonic A1AR activation. These results demonstrate that the different resting membrane properties between dorsal and ventral CA1 neurons are due, in part, to higher A1AR-mediated GIRK activity in dorsal CA1 neurons.
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Affiliation(s)
- Chung Sub Kim
- Department of Neuroscience and Center for Learning and Memory, University of Texas at Austin, Austin, Texas
| | - Daniel Johnston
- Department of Neuroscience and Center for Learning and Memory, University of Texas at Austin, Austin, Texas
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26
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Pofantis H, Papatheodoropoulos C. The α5GABAA receptor modulates the induction of long-term potentiation at ventral but not dorsal CA1 hippocampal synapses. Synapse 2014; 68:394-401. [PMID: 24823837 DOI: 10.1002/syn.21751] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 04/18/2014] [Accepted: 05/03/2014] [Indexed: 11/08/2022]
Abstract
The hippocampal synapses display conspicuous ability for long-term plasticity which is thought to underlie learning and memory. Growing evidence shows that this ability differs along the long axis of the hippocampus, with the ventral CA1 hippocampal synapses displaying remarkably lower ability for long-term potentiation (LTP) compared with their dorsal counterpart when activated with high-frequency stimulation. Here, we show that low frequency, 10 Hz stimulation induced LTP more reliably in dorsal than in ventral CA1 field. Blockade of alpha5 subunit-containing GABAA receptors eliminated the difference between dorsal and ventral hippocampus. We propose that α5GABAA receptor-mediated activity plays a crucial role in regulating the threshold for induction of LTP especially at the ventral CA1 hippocampal synapses. This might have important implications for the functional specialization along the hippocampus.
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Affiliation(s)
- Hermes Pofantis
- Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, 26504, Rion, Patras, Greece
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27
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Kenney J, Manahan-Vaughan D. NMDA receptor-dependent synaptic plasticity in dorsal and intermediate hippocampus exhibits distinct frequency-dependent profiles. Neuropharmacology 2013; 74:108-18. [PMID: 23499810 DOI: 10.1016/j.neuropharm.2013.02.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 02/12/2013] [Accepted: 02/19/2013] [Indexed: 11/17/2022]
Abstract
The hippocampus may be functionally differentiated along its dorsoventral axis. In contrast to the wealth of data available on synaptic plasticity mechanisms in the dorsal hippocampus, little is known about synaptic plasticity processes in the intermediate hippocampus. Behavioral data suggest that this structure may play a distinct role in learning and memory. Here, we compared amplitudes, frequency-dependency and persistency of long-term potentiation (LTP) and long-term depression (LTD) in the dorsal (DDG) and intermediate dentate gyrus (IDG). In freely moving rats, high-frequency stimulation (HFS) at 200 Hz (10 burst of 15 stimuli) elicited LTP of similar magnitude in both structures that persisted for over 24 h. The intermediate dentate gyrus is more likely to exhibit persistent LTP than its dorsal counterpart, however: HFS at 200 Hz (3 or 1 burst(s)) or 100 Hz elicited short-term potentiation (STP) in DDG, unlike in the IDG, where LTP could be recorded for at least 4 h. Whereas low frequency stimulation (LFS) at 1 Hz elicited long-lasting LTD (>24 h) in the DDG, it had no significant effect on fEPSP profile in the IDG. LFS at 2 Hz elicited short-term depression in DDG and had no effect in IDG. LTP in both IDG and DDG required activation of N-methyl-D-aspartate receptors. Paired-pulse and input-output responses differed in IDG and DDG. Our data suggest that afferent input from the entorhinal cortex generates a different response profile in the dorsal vs. intermediate DG, which may in turn relate to their postulated distinct roles in synaptic information processing and memory formation. This article is part of the Special Issue entitled 'Glutamate Receptor-Dependent Synaptic Plasticity'.
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Affiliation(s)
- Jana Kenney
- Ruhr University Bochum, Medical Faculty, Department of Neurophysiology, 44780 Bochum, Germany
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28
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Nagy JI. Evidence for connexin36 localization at hippocampal mossy fiber terminals suggesting mixed chemical/electrical transmission by granule cells. Brain Res 2012; 1487:107-22. [PMID: 22771400 PMCID: PMC3501615 DOI: 10.1016/j.brainres.2012.05.064] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 05/14/2012] [Accepted: 05/15/2012] [Indexed: 11/25/2022]
Abstract
Electrical synaptic transmission via gap junctions has become an accepted feature of neuronal communication in the mammalian brain, and occurs often between dendrites of interneurons in major brain structures, including the hippocampus. Electrical and dye-coupling has also been reported to occur between pyramidal cells in the hippocampus, but ultrastructurally-identified gap junctions between these cells have so far eluded detection. Gap junctions can be formed by nerve terminals, where they contribute the electrical component of mixed chemical/electrical synaptic transmission, but mixed synapses have only rarely been described in mammalian CNS. Here, we used immunofluorescence localization of the major gap junction forming protein connexin36 to examine its possible association with hippocampal pyramidal cells. In addition to labeling associated with gap junctions between dendrites of parvalbumin-positive interneurons, a high density of fine, punctate immunolabeling for Cx36, non-overlapping with parvalbumin, was found in subregions of the stratum lucidum in the ventral hippocampus of rat brain. A high percentage of Cx36-positive puncta in the stratum lucidum was localized to mossy fiber terminals, as indicated by co-localization of Cx36-puncta with the mossy terminal marker vesicular glutamate transporter-1, as well as with other proteins that are highly concentrated in, and diagnostic markers of, these terminals. These results suggest that mossy fiber terminals abundantly form mixed chemical/electrical synapses with pyramidal cells, where they may serve as intermediaries for the reported electrical and dye-coupling between ensembles of these principal cells. This article is part of a Special Issue entitled Electrical Synapses.
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Affiliation(s)
- James I Nagy
- Department of Physiology, Faculty of Medicine, University of Manitoba, 745 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E 0J9.
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Dougherty KA, Islam T, Johnston D. Intrinsic excitability of CA1 pyramidal neurones from the rat dorsal and ventral hippocampus. J Physiol 2012; 590:5707-22. [PMID: 22988138 DOI: 10.1113/jphysiol.2012.242693] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The hippocampus has a central role in learning and memory. Although once considered a relatively homogenous structure along the longitudinal axis, it has become clear that the rodent hippocampus can be anatomically and functionally divided into a dorsal component generally associated with spatial navigation, and a ventral component primarily associated with non-spatial functions that involve an emotional component. The ventral hippocampus (VHC) is also more sensitive to epileptogenic stimuli than the dorsal hippocampus (DHC), and seizures tend to originate in the VHC before spreading to other brain regions. Although synaptic and biochemical differences in DHC and VHC have been investigated, the intrinsic excitability of individual neurones from the DHC and VHC has received surprisingly little attention. In this study, we have characterized the intrinsic electrophysiological properties of CA1 pyramidal neurones from the DHC and the VHC using the whole-cell current-clamp method. Our results demonstrate that somatic current injections of equal magnitude elicit significantly more action potentials in VHC neurones than DHC neurones, and that this difference stems from the more depolarized resting membrane potential (RMP; 7 mV) and higher input resistance (R(in); 46 M measured from RMP) observed in VHC neurones. These differences in RMP and R(in) were also observed in dendritic whole-cell current-clamp recordings. Furthermore, morphological reconstructions of individual neurones revealed significant differences in the dendritic branching pattern between DHC and VHC neurones that could, in principle, contribute to the lower somatic R(in) of DHC neurones. Together, our results highlight significant differences in the intrinsic electrophysiological properties of CA1 pyramidal neurones across the longitudinal hippocampal axis, and suggest that VHC neurones are intrinsically more excitable than DHC neurones. This difference is likely to predispose the VHC to hyperexcitability.
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Affiliation(s)
- Kelly A Dougherty
- Center for Learning and Memory, University of Texas at Austin, 100 East 24th St Room 4.310, Austin, TX 78712, USA.
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Mikroulis AV, Psarropoulou C. Endogenous ACh effects on NMDA-induced interictal-like discharges along the septotemporal hippocampal axis of adult rats and their modulation by an early life generalized seizure. Epilepsia 2012; 53:879-87. [DOI: 10.1111/j.1528-1167.2012.03440.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Christensen T, Bisgaard C, Nielsen H, Wiborg O. Transcriptome differentiation along the dorso–ventral axis in laser-captured microdissected rat hippocampal granular cell layer. Neuroscience 2010; 170:731-41. [DOI: 10.1016/j.neuroscience.2010.07.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 07/02/2010] [Accepted: 07/06/2010] [Indexed: 12/31/2022]
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32
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Kouvaras E, Asprodini EK, Asouchidou I, Vasilaki A, Kilindris T, Michaloudis D, Koukoutianou I, Papatheodoropoulos C, Kostopoulos G. Fentanyl treatment reduces GABAergic inhibition in the CA1 area of the hippocampus 24 h after acute exposure to the drug. Neuropharmacology 2008; 55:1172-82. [PMID: 18706433 DOI: 10.1016/j.neuropharm.2008.07.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 05/27/2008] [Accepted: 07/17/2008] [Indexed: 11/19/2022]
Abstract
The effect of in vivo fentanyl treatment on synaptic transmission was studied in the CA1 area of the rat hippocampus. Animals were treated either with saline or fentanyl (4 x 80 microg/kg, s.c./15 min). Intracellular in vitro recordings were obtained, 24 h after treatment, from CA1 pyramidal neurons. No difference in pyramidal neuron basic membrane properties or postsynaptic membrane excitability was observed between neurons from saline- and fentanyl-treated animals. The peak amplitude of fast (f-) and slow (s-) components of IPSPs elicited in standard ACSF and the peak amplitude and rate of rise of isolated f- and s-IPSPs elicited in the presence of antagonists (CNQX, 10 microM; AP-5, 10 microM; CGP 55845, 1 microM; and bicuculline methochloride, 10 microM), in response to various stimulus intensities, was smaller in fentanyl-treated animals. Conversely, the rising slope of excitatory responses was similar in neurons from saline- and fentanyl-treated animals. Furthermore, in fentanyl-treated animals, lower stimulus strengths were required to elicit subthreshold excitatory responses of the same amplitude suggesting that acute exposure to fentanyl increases susceptibility of pyramidal neurons to presynaptic stimulation. GABA immunohistochemistry revealed lower GABA content in processes and neuronal somata suggesting diminished GABA release onto pyramidal neurons. We conclude that acute in vivo exposure to fentanyl is sufficient to induce long-lasting reduction in GABA-mediated transmission, rather, than enhanced excitatory transmission or modulation of the intrinsic excitability of pyramidal neurons. These findings provide evidence regarding the mechanisms involved in the early stages of tolerance development towards the analgesic effects of opioids.
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Affiliation(s)
- E Kouvaras
- Laboratory of Pharmacology, School of Medicine, University of Thessaly, Faculty of Health Sciences, 22 Papakiriazi Street, 41222 Larissa, Greece
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Liagkouras I, Michaloudi H, Batzios C, Psaroulis D, Georgiadis M, Künzle H, Papadopoulos GC. Pyramidal neurons in the septal and temporal CA1 field of the human and hedgehog tenrec hippocampus. Brain Res 2008; 1218:35-46. [DOI: 10.1016/j.brainres.2008.04.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 04/17/2008] [Accepted: 04/20/2008] [Indexed: 10/22/2022]
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Varying magnitude of GABAergic recurrent inhibition enhancement by different sedative/anesthetic agents in dorsal and ventral hippocampus. Brain Res 2008; 1207:43-59. [DOI: 10.1016/j.brainres.2008.02.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2007] [Revised: 01/28/2008] [Accepted: 02/03/2008] [Indexed: 11/17/2022]
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35
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Differential pharmacological properties of GABAA/benzodiazepine receptor complex in dorsal compared to ventral rat hippocampus. Neurochem Int 2007; 52:1019-29. [PMID: 18069090 DOI: 10.1016/j.neuint.2007.10.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 10/15/2007] [Accepted: 10/26/2007] [Indexed: 11/21/2022]
Abstract
Several studies have indicated a functional differentiation across the septotemporal axis of rat hippocampus. Our previous results have shown that the alpha 1 beta 2 gamma 2-GABAA receptor subtype dominates in dorsal hippocampus (DH), while the alpha 2 beta 1 gamma 2-subtype prevails in ventral hippocampus (VH). We therefore studied possible differences in the pharmacological properties and receptor binding parameters of the GABAA receptor subtypes between DH and VH, by examining: (1)(a) the specific binding of [3H]-flunitrazepam (Benzodiazepine sites agonist) by using quantitative autoradiography, (b) the kinetic parameters of [3H]-flunitrazepam specific binding, by using the "wipe off" technique and (2) the competitive displacement of [3H]-flunitrazepam binding by using zolpidem (selective agonist of the alpha 1-subtype) and L-655,708 (selective inverse agonist of the alpha 5-subtype) and the enhancement of [3H]-flunitrazepam binding by using etomidate (selective positive modulator of the beta 2-subunit), in an autoradiographical saturation kinetic study. Our results showed in VH compared to DH: (A) lower level of [3H]-flunitrazepam binding, apparently due to weaker binding affinity (higher KD value), since no differences in the Bmax value could be detected, (B) higher IC50 values for zolpidem and lower IC50 values for L-655,708 and (C) higher EC50 values for etomidate. In conclusion, the lower binding for zolpidem and etomidate and the higher binding for L-655,708 observed in VH support the evidence that the alpha 1 beta 2 gamma 2-GABAA receptor subtype dominates in DH and the alpha 5-subtype prevails in VH. Further, our results suggest differential pharmacological effects of the benzodiazepines in DH compared to VH, with the sedative effects being more potent in the dorsal hippocampus.
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36
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Petrides T, Georgopoulos P, Kostopoulos G, Papatheodoropoulos C. The GABAA receptor-mediated recurrent inhibition in ventral compared with dorsal CA1 hippocampal region is weaker, decays faster and lasts less. Exp Brain Res 2007; 177:370-83. [PMID: 16988819 DOI: 10.1007/s00221-006-0681-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Accepted: 08/15/2006] [Indexed: 11/26/2022]
Abstract
Hippocampal functions appear to be segregated along the dorso-ventral axis of the structure. Differences at the cellular and local neuronal network level may be involved in this functional segregation. In this study the characteristics of CA1 recurrent inhibition (RI) were measured and compared between dorsal (DH, n = 95) and ventral (VH, n = 60) hippocampal slices, using recordings of suprathreshold field potentials. RI strength was estimated as the percentile decrease of the population spike (PS) amplitude evoked with an orthodromic stimulus (at the Schaffer collaterals) when preceded by an antidromic stimulus (at the alveus). Varying the interpulse interval (IPI) between the two stimuli, we estimated RI duration. Alvear stimulation produced significant PS suppression in both VH and DH at every IPI tested, from 10 to 270 ms. Moreover, gradually more oblique DH (but not VH) slices displayed increasing RI, which at IPIs < or = 125 ms was reversibly abolished by the GABAA receptor antagonist picrotoxin (10 microM). The GABAA-mediated RI, measured under the blockade of GABAB receptors, was weaker, decayed faster and lasted less in VH compared to DH slices, regardless of the slice orientation. Specifically, in VH compared to DH, the PS suppression at 20 ms was 34.4 +/- 4.5% versus 69.9 +/- 6.5% (P < 0.001), the time constant of RI decay was 29 +/- 2.4 versus 87.5 +/- 13.6 ms (P < 0.01) and the duration was 50 versus 125 ms (P < 0.001). Thus, GABAA-mediated RI may control the CA1 excitatory output less effectively in VH compared to DH. The observed dorso-ventral differences in RI contribute to the longitudinal diversification of the structure and may underlie to some extent the region-specificity of hippocampal functions.
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Affiliation(s)
- Theodoros Petrides
- Department of Physiology, Medical School, University of Patras, 26 504 Patras, Greece
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37
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Kawashima H, Izaki Y, Grace AA, Takita M. Cooperativity between hippocampal–prefrontal short-term plasticity through associative long-term potentiation. Brain Res 2006; 1109:37-44. [PMID: 16859647 DOI: 10.1016/j.brainres.2006.06.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 06/08/2006] [Accepted: 06/13/2006] [Indexed: 11/29/2022]
Abstract
The hippocampal-medial prefrontal cortex (mPFC) pathway provides highly convergent input to the mPFC in rats and shows two types of short-term plasticity in terms of paired-pulse facilitation (PPF) of the field potential under urethane anesthesia. We now report that stimulating either the dorsal or ventral subregions of the posterior hippocampus elicited PPF (by about 335 and 120%, respectively) of field potentials recorded in the mPFC at 100 ms interpulse interval. This PPF-like interaction occurred when projections were stimulated in the ventral-dorsal order (by about 200% of the single-pulsed response), but not vice versa. When weak long-term potentiation (LTP) of the dorsal projection was evoked simultaneously with strong LTP of the ventral projection, an associative effect was revealed (about +55%), although the magnitudes of LTP in each projection were not correlated. Even when the impermutable PPF-like facilitation was further enhanced (by about +120%), the enhancement was not correlated with either form of LTP, but exhibited the interaction of changes in the dorsal PPF, rather than in the heterotopic priming effect through the ventral projection. Moreover, this change was correlated with the associated LTP ratio of dorsal to ventral projection LTP (i.e., LTP associativity). Larger increases in LTP associativity correlated with greater impermutable PPF-like facilitation; in addition, there was hardly attenuation of the response to the dorsal projection by subsequent electrolytic lesions of the ventral subregion. These results indicate that the mPFC functionally integrates discrete sources of hippocampal information via cooperativity between short- and long-term plasticity.
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Affiliation(s)
- Hitoshi Kawashima
- Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
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38
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Derchansky M, Rokni D, Rick JT, Wennberg R, Bardakjian BL, Zhang L, Yarom Y, Carlen PL. Bidirectional multisite seizure propagation in the intact isolated hippocampus: the multifocality of the seizure "focus". Neurobiol Dis 2006; 23:312-28. [PMID: 16815026 DOI: 10.1016/j.nbd.2006.03.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/09/2006] [Accepted: 03/17/2006] [Indexed: 11/29/2022] Open
Abstract
Localizing the seizure focus is difficult and frequently, multiple sites are found. This reflects our poor understanding of the fundamental mechanisms of seizure generation and propagation. We used multisite electrophysiological recordings in two seizure models and voltage-sensitive dye imaging, to spatiotemporally characterize the initiation and propagation of seizures in an intact epileptogenic brain region, the isolated hippocampus. In low-magnesium perfusate, seizures always originated in the temporal region, and propagated along the septotemporal axis to the septal region. After the seizure spread across the hippocampus, the bursts within a seizure became bidirectional, with different propagation patterns at different frequencies. When the intact hippocampus was separated along the septotemporal axis, independent bidirectional activity was observed in the two halves, and region-specific cuts to the tissue reveal that the CA3 region is critical for seizure generation and propagation. In a second seizure model, using focal tetanic stimulation of the septal and temporal CA3 region, seizures always originated at the stimulated site with bidirectionality later developing at different frequencies, as noted in the low magnesium model, behavior compatible with coupled neuronal network oscillators. These data provide novel insights into the dynamic multifocality of seizure onset and propagation, revealing that the current concept of a single seizure "focus" is complex.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, Canada
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39
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Sotiriou E, Papatheodoropoulos C, Angelatou F. Differential expression of gamma-aminobutyric acid--a receptor subunits in rat dorsal and ventral hippocampus. J Neurosci Res 2006; 82:690-700. [PMID: 16273537 DOI: 10.1002/jnr.20670] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent data demonstrate weaker gamma-aminobutyric acid (GABA)-ergic inhibition in ventral (VH) compared with dorsal (DH) hippocampus. Therefore, we examined possible differences regarding the GABAA receptors between VH and DH as follows: 1) the expression of the GABAA receptor subunits (alpha1/2/4/5, beta1/2/3, gamma2, delta) mRNA and protein and 2) the quantitative distribution and kinetic parameters of [3H] muscimol (GABAA receptor agonist) binding. VH compared with DH showed: 1) lower levels for alpha1, beta2, gamma2 but higher levels for alpha2 and beta1 subunits in CA1, CA2, and CA3, the differences being more pronounced in CA1 region; in the CA1 region, the mRNA levels of alpha5 were higher, whereas those of alpha4 subunit were slightly lower; in dentate gyrus, the mRNA levels of alpha4, beta3, and delta subunits were significantly lower, presumably suggesting a lower expression of the alpha4/beta3/delta receptor subtype; and 2) lower levels of [3H]muscimol binding, with the lowest value observed in CA1, apparently resulting from weaker binding affinity, insofar as the KD values were higher in VH, whereas the Bmax values were similar between DH and VH. The differences in the subunit expression and the lower affinity of GABAA receptor binding observed predominantly in the CA1 region of VH suggest that the alpha1/beta2/gamma2 GABAA receptor subtype dominates in DH, and the alpha2/beta1/gamma2 subtype prevails in VH. This could underlie the lower GABAA-mediated inhibition observed in VH and, to some extent, explain 1) the higher liability of VH for epileptic activity and 2) the differential involvement of DH and VH in cognitive and emotional processes.
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Affiliation(s)
- Evangelos Sotiriou
- Physiology Department, Medical School, University of Patras, Patras, Greece
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40
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Maggio N, Segal M. Unique regulation of long term potentiation in the rat ventral hippocampus. Hippocampus 2006; 17:10-25. [PMID: 17094146 DOI: 10.1002/hipo.20237] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Morphological and electrophysiological evidence has been accumulated in recent years to indicate that a functional gradient exists along the septo-temporal axis of the hippocampus such that spatial memory is associated primarily with the dorsal (septal) sector while the functions of the ventral sector are not yet clearly defined. Also, the ventral hippocampus (VH) is reported to express a much smaller long term potentiation of responses to afferent stimulation than the dorsal sector. In the present study, we first confirmed that CA1 region of VH slices expresses significantly smaller LTP than the dorsal hippocampus. Strikingly, much larger LTP was obtained in VH slices following low frequency priming stimulation applied prior to the tetanic stimulation. DHPG ((S)-3,5-Dihydroxyphenylglycine hydrate) a metabotropic glutamate receptor agonist, produced a similar potentiating effect on LTP as that produced by the priming stimulation. In both cases, the spectral analysis of spontaneous electrical activity recorded from the same location in the slice revealed an increase in peak amplitude around 30 Hz. MCPG, a metabotropic glutamate receptor antagonist, and both thapsigargin and cyclopiazonic acid, inhibitors of Ca(2+) release from stores, blocked the potentiating action of both DHPG and the priming stimulation. These results indicate that the ventral hippocampus possesses different network properties compared to the dorsal hippocampus and that its ability to undergo plastic changes is controlled by a metabotropic glutamate receptor.
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Affiliation(s)
- Nicola Maggio
- Department of Neurobiology, The Weizmann Institute, Rehovot, Israel
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41
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Pandis C, Sotiriou E, Kouvaras E, Asprodini E, Papatheodoropoulos C, Angelatou F. Differential expression of NMDA and AMPA receptor subunits in rat dorsal and ventral hippocampus. Neuroscience 2006; 140:163-75. [PMID: 16542781 DOI: 10.1016/j.neuroscience.2006.02.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 02/01/2006] [Accepted: 02/02/2006] [Indexed: 12/12/2022]
Abstract
Several studies have demonstrated anatomical and functional segregation along the dorsoventral axis of the hippocampus. This study examined the possible differences in the AMPA and NMDA receptor subunit composition and receptor binding parameters between dorsal and ventral hippocampus, since several evidence suggest diversification of NMDA receptor-dependent processes between the two hippocampal poles. Three sets of rat dorsal and ventral hippocampus slices were prepared: 1) transverse slices for examining a) the expression of the AMPA (GluRA, GluRB, GluRC) and NMDA (NR1, NR2A, NR2B) subunits mRNA using in situ hybridization, b) the protein expression of NR2A and NR2B subunits using Western blotting, and c) by using quantitative autoradiography, c(1)) the specific binding of the AMPA receptor agonist [(3)H]AMPA and c(2)) the specific binding of the NMDA receptor antagonist [(3)H]MK-801, 2) longitudinal slices containing only the cornus ammonis 1 (CA1) region for performing [(3)H]MK-801 saturation experiments and 3) transverse slices for electrophysiological measures of NMDA receptor-mediated excitatory postsynaptic potentials. Ventral compared with dorsal hippocampus showed for NMDA receptors: 1) lower levels of mRNA and protein expression for NR2A and NR2B subunits in CA1 with the ratio of NR2A /NR2B differing between the two poles and 2) lower levels of [(3)H]MK-801 binding in the ventral hippocampus, with the lowest value observed in CA1, apparently resulting from a decreased receptor density since the B(max) value was lower in ventral hippocampus. For the AMPA receptors CA1 our results showed in ventral hippocampus compared with dorsal hippocampus: 1) lower levels of mRNA expression for GluRA, GluRB and GluRC subunits, which were more pronounced in CA1 and in dentate gyrus region and 2) lower levels of [(3)H]AMPA binding. Intracellular recordings obtained from pyramidal neurons in CA1 showed longer NMDA receptor-mediated excitatory postsynaptic potentials in ventral hippocampus compared with dorsal hippocampus. In conclusion, the differences in the subunit mRNA and protein expression of NMDA and AMPA receptors as well as the lower density of their binding sites observed in ventral hippocampus compared with dorsal hippocampus suggest that the glutamatergic function differs between the two hippocampal poles. Consistently, the lower value of the ratio NR2A/NR2B seen in the ventral part would imply that the ventral hippocampus NMDA receptor subtype is functionally different than the dorsal hippocampus subtype, as supported by our intracellular recordings. This could be related to the lower ability of ventral hippocampus for long-term synaptic plasticity and to the higher involvement of the NMDA receptors in the epileptiform discharges, observed in ventral hippocampus compared with dorsal hippocampus.
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Affiliation(s)
- C Pandis
- Physiology Department, Medical School, University of Patras, 26500 Rio, Patras, Greece
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42
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Papatheodoropoulos C, Moschovos C, Kostopoulos G. Greater contribution of N-methyl-D-aspartic acid receptors in ventral compared to dorsal hippocampal slices in the expression and long-term maintenance of epileptiform activity. Neuroscience 2005; 135:765-79. [PMID: 16154282 DOI: 10.1016/j.neuroscience.2005.06.024] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 06/12/2005] [Accepted: 06/14/2005] [Indexed: 10/25/2022]
Abstract
Functional segregation along the dorso-ventral axis of the hippocampus is a developing concept. The higher susceptibility of the ventral hippocampus to epileptic activity compared with dorsal hippocampus is one of the main features, which still has obscure mechanisms. Using the model of magnesium-free medium and field recordings, single epileptiform discharges displayed higher incidence (77% vs 57%), rate (41.7+/-3.1 vs 13.5+/-0.7 events/min), duration (173.9+/-17.7 vs 116.8+/-13.6 ms) and intensity (coastline, 25.4+/-2.5 vs 9.5+/-1.8) in ventral compared with dorsal rat hippocampal slices. In addition, the decay phase of the evoked synaptic potentials was 110% slower in ventral slices. The N-methyl-D-aspartate (NMDA) receptor antagonist d-(-)-2-amino-5-phosphonopentanoic acid (50-100 microM) decreased the discharge rate and coastline similarly in ventral and dorsal slices, but it shortened the discharges in ventral slices (by 40%) only. The NMDA receptor antagonist 3-((R)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (10 microM) decreased the rate in both groups and additionally shortened discharges in both kinds of slices, an effect which was greater in ventral ones (31% vs 13%). Furthermore, both drugs shortened the evoked potentials more in ventral (77%) than in dorsal slices (52%). On the other hand, 1 microM of 3-((R)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid shortened the discharges and evoked synaptic potentials only in ventral slices, and slowed down the discharge rate only in dorsal slices. Addition of NMDA, in the magnesium-free medium, enhanced activity in both kinds of slices. At 5 and 10 microM of NMDA 51% of the ventral but only 9% of the dorsal slices displayed persistent epileptiform discharges, which were recorded for at least one hour after reintroduction of magnesium in the medium. At 10-20 microM the enhancement of activity was transient, followed by suppression of discharges in 40% and 76% of the ventral and dorsal slices, respectively. Most of the slices having experienced suppression did not develop persistent activity. We propose that the NMDA receptors contribute to the higher susceptibility of the ventral hippocampus to expression and long-term maintenance of epileptiform discharges. This diversification may be related to other aspects of hippocampal dorso-ventral functional segregation.
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Affiliation(s)
- C Papatheodoropoulos
- Department of Physiology, Medical School, University of Patras, 26500 Patras, Greece.
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Derchansky M, Shahar E, Wennberg RA, Samoilova M, Jahromi SS, Abdelmalik PA, Zhang L, Carlen PL. Model of frequent, recurrent, and spontaneous seizures in the intact mouse hippocampus. Hippocampus 2005; 14:935-47. [PMID: 15390177 DOI: 10.1002/hipo.20007] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study presents a model of chronic, recurrent, spontaneous seizures in the intact isolated hippocampal preparation from mice aged P8-P25. Field activity from the CA1 pyramidal cell layer was recorded and recurrent, spontaneous seizure-like events (SLEs) were observed in the presence of low Mg2+ (0.25 mM) artificial cerebrospinal fluid (ACSF). Hippocampi also showed interictal epileptiform discharges (IEDs) of 0.9-4.2 Hz occurring between seizures. No age-specific differences were found in SLE occurrence (2 SLEs per 10 min, on average), duration, and corresponding frequencies. After long exposure to low Mg2+ ACSF (>3 h), SLEs were completely reversible within minutes with the application of normal (2 mM Mg2+) ACSF. The AMPA antagonist, CNQX, blocked all epileptiform activity, whereas the NMDA antagonist, APV, did not. The gamma-aminobutyric acid (GABA)A antagonist, bicuculline, attenuated and fragmented SLEs, implicating interneurons in SLE generation. The L-type Ca2+ blocker, nifedipine, enhanced epileptiform activity. Analysis of dual site recordings along the septotemporal hippocampus demonstrated that epileptiform activity began first in the temporal pole of the hippocampus, as illustrated by disconnection experiments. Once an SLE had been established, however, the septal hippocampus was sometimes seen to lead the epileptiform activity. The whole hippocampus with intact local circuitry, treated with low Mg2+, provides a realistic model of recurrent spontaneous seizures, which may be used, in normal and genetically modified mice, to study the dynamics of seizures and seizure evolution, as well as the mechanisms of action of anti-epileptic drugs and other therapeutic modalities.
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Affiliation(s)
- M Derchansky
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, Ontario, Toronto, Canada
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