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Kowalczyk T, Staszelis A, Bocian R, Siwiec M, Sowa JE, Tokarski K, Kaźmierska-Grębowska P, Caban B. Posterior hypothalamic theta rhythm: Electrophysiological basis and involvement of glutamatergic receptors. Hippocampus 2023; 33:844-861. [PMID: 36688619 DOI: 10.1002/hipo.23500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 12/20/2022] [Accepted: 12/29/2022] [Indexed: 01/24/2023]
Abstract
The posterior hypothalamic area (PHa), including the supramammillary nucleus (SuM) and posterior hypothalamic nuclei, forms a crucial part of the ascending brainstem hippocampal synchronizing pathway, that is involved in the frequency programming and modulation of rhythmic theta activity generated in limbic structures. Recent investigations show that in addition to being a modulator of limbic theta activity, the PHa is capable of producing well-synchronized local theta field potentials by itself. The purpose of this study was to examine the ability of the PHa to generate theta field potentials and accompanying cell discharges in response to glutamatergic stimulation under both in vitro and in vivo conditions. The second objective was to examine the electrophysiological properties of neurons located in the SuM and posterior hypothalamic nuclei. Extracellular in vivo and in vitro as well as intracellular in vitro experiments revealed that glutamatergic stimulation of PHa with kainic acid induces well-synchronized local theta field oscillations in both the supramammillary and posterior hypothalamic nuclei. Furthermore, the glutamatergic PHa theta rhythm recorded extracellularly was accompanied by the activity of specific subtypes of theta-related neurons. We identify, for the first time, a subpopulation of supramammillary and posterior hypothalamic neurons that express clear subthreshold membrane potential oscillations in the theta frequency range.
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Affiliation(s)
- Tomasz Kowalczyk
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
| | - Agata Staszelis
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
| | - Renata Bocian
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
| | - Marcin Siwiec
- Department of Physiology, Maj Institute of Pharmacology Polish Academy of Sciences, Krakow, Poland
| | - Joanna E Sowa
- Department of Physiology, Maj Institute of Pharmacology Polish Academy of Sciences, Krakow, Poland
| | - Krzysztof Tokarski
- Department of Physiology, Maj Institute of Pharmacology Polish Academy of Sciences, Krakow, Poland
| | | | - Bartosz Caban
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
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The Role of the Posterior Hypothalamus in the Modulation and Production of Rhythmic Theta Oscillations. Neuroscience 2021; 470:100-115. [PMID: 34271089 DOI: 10.1016/j.neuroscience.2021.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 06/18/2021] [Accepted: 07/05/2021] [Indexed: 11/24/2022]
Abstract
Theta rhythm recorded as an extracellular synchronous field potential is generated in a number of brain sites including the hippocampus. The physiological occurrence of hippocampal theta rhythm is associated with the activation of a number of structures forming the ascending brainstem-hippocampal synchronizing pathway. Experimental evidence indicates that the supramammillary nucleus and posterior hypothalamic nuclei, considered as the posterior hypothalamic area, comprise a critical node of this ascending pathway. The posterior hypothalamic area plays an important role in movement control, place-learning, memory processing, emotion and arousal. In the light of multiplicity of functions of the posterior hypothalamic area and the influence of theta field oscillations on a number of neural processes, it is the authors' intent to summarize the data concerning the involvement of the supramammillary nucleus and posterior hypothalamic nuclei in the modulation of limbic theta rhythmicity as well as the ability of these brain structures to independently generate theta rhythmicity.
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Staszelis A, Kowalczyk T. The role of the posterior hypothalamic area
in the generation of theta rhythm. POSTEP HIG MED DOSW 2021. [DOI: 10.5604/01.3001.0014.9333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Theta rhythm is one of the best synchronized patterns of the oscillatory activity recorded in
the mammalian brain. In humans, this rhythm is associated with REM sleep, spatial navigation,
memory functions, analytical and language processes. On the other hand, it can be treated as
a non-specific marker of such pathological states of the central nervous system as Alzheimer’s
disease or epilepsy. The hippocampal formation is the key structure involved in the generation
of this bioelectric phenomenon, both in humans and rodents (the most commonly studied laboratory
animals). Theta rhythm appearance in the hippocampus is dependent on the interaction
of multiple different structures of the nervous system. One of them is the posterior hypothalamic
area (PHa), which constitutes a crucial part of the neuronal system modulating the ability
of the hippocampal formation to generate theta rhythm. Although the research results encompassed
in this paper emphasize the essential role of the PHa as a modulator of the hippocampal
theta rhythm, it was the authors’ intent to indicate that this area is also capable of generating
local rhythmical theta oscillations, independently of the influence of other brain structures.
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Affiliation(s)
- Agata Staszelis
- Katedra Neurobiologii, Wydział Biologii i Ochrony Środowiska, Uniwersytet Łódzki, Łódź
| | - Tomasz Kowalczyk
- Katedra Neurobiologii, Wydział Biologii i Ochrony Środowiska, Uniwersytet Łódzki, Łódź
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Sil’kis IG. Possible Mechanisms of the Complex Effects of Acetylcholine on Theta Activity, Learning, and Memory. NEUROCHEM J+ 2019. [DOI: 10.1134/s1819712419020119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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MacGregor DJ, Leng G. Emergent decision-making behaviour and rhythm generation in a computational model of the ventromedial nucleus of the hypothalamus. PLoS Comput Biol 2019; 15:e1007092. [PMID: 31158265 PMCID: PMC6564049 DOI: 10.1371/journal.pcbi.1007092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 06/13/2019] [Accepted: 05/13/2019] [Indexed: 12/18/2022] Open
Abstract
The ventromedial nucleus of the hypothalamus (VMN) has an important role in diverse behaviours. The common involvement in these of sex steroids, nutritionally-related signals, and emotional inputs from other brain areas, suggests that, at any given time, its output is in one of a discrete number of possible states corresponding to discrete motivational drives. Here we explored how networks of VMN neurons might generate such a decision-making architecture. We began with minimalist assumptions about the intrinsic properties of VMN neurons inferred from electrophysiological recordings of these neurons in rats in vivo, using an integrate-and-fire based model modified to simulate activity-dependent post-spike changes in neuronal excitability. We used a genetic algorithm based method to fit model parameters to the statistical features of spike patterning in each cell. The spike patterns in both recorded cells and model cells were assessed by analysis of interspike interval distributions and of the index of dispersion of firing rate over different binwidths. Simpler patterned cells could be closely matched by single neuron models incorporating a hyperpolarising afterpotential and either a slow afterhyperpolarisation or a depolarising afterpotential, but many others could not. We then constructed network models with the challenge of explaining the more complex patterns. We assumed that neurons of a given type (with heterogeneity introduced by independently random patterns of external input) were mutually interconnected at random by excitatory synaptic connections (with a variable delay and a random chance of failure). Simple network models of one or two cell types were able to explain the more complex patterns. We then explored the information processing features of such networks that might be relevant for a decision-making network. We concluded that rhythm generation (in the slow theta range) and bistability arise as emergent properties of networks of heterogeneous VMN neurons.
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Affiliation(s)
- Duncan J. MacGregor
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
| | - Gareth Leng
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
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6
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GABAergic mediation of hippocampal theta rhythm induced by stimulation of the vagal nerve. Brain Res Bull 2019; 147:110-123. [DOI: 10.1016/j.brainresbull.2019.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 02/18/2019] [Indexed: 12/22/2022]
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Lévesque M, Avoli M. Carbachol-Induced theta-like oscillations in the rodent brain limbic system: Underlying mechanisms and significance. Neurosci Biobehav Rev 2018; 95:406-420. [PMID: 30381251 DOI: 10.1016/j.neubiorev.2018.10.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 09/25/2018] [Accepted: 10/24/2018] [Indexed: 12/13/2022]
Abstract
Theta oscillations (4-12 Hz) represent one of the most prominent physiological oscillatory activity in the mammalian EEG. They are observed in several areas of the hippocampus and in parahippocampal structures. Theta oscillations play important roles in modulating synaptic plasticity during memory and learning; moreover, they are dependent on septal cholinergic inputs. Theta oscillations can be reproduced in vitro in several regions of the temporal lobe in the absence of the septum by employing the cholinergic agonist carbachol (CCh). Here, we review the mechanisms underlying CCh-induced theta oscillations. We address: (i) the ability of temporal lobe neuronal networks to oscillate independently at theta frequency during CCh treatment; (ii) the contribution of intrinsic ionic currents; (iii) the participation of principal cells and interneurons; and (iv) their pharmacological profiles. We also discuss the similarities between CCh-induced theta oscillations and physiological type II theta activity, as well as their roles in synaptic plasticity. Finally, we consider experimental evidence pointing to the contribution of spontaneous and CCh-induced theta activity to epileptiform synchronization.
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Affiliation(s)
- Maxime Lévesque
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, PQ, H3A 2B4, Canada
| | - Massimo Avoli
- Montreal Neurological Institute and Departments of Neurology & Neurosurgery, and of Physiology, McGill University, 3801 University Street, Montréal, PQ, H3A 2B4, Canada; Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
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Caban B, Staszelis A, Kazmierska P, Kowalczyk T, Konopacki J. Postnatal Development of the Posterior Hypothalamic Theta Rhythm and Local Cell Discharges in Rat Brain Slices. Dev Neurobiol 2018; 78:1049-1063. [DOI: 10.1002/dneu.22628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 06/25/2018] [Accepted: 06/26/2018] [Indexed: 02/05/2023]
Affiliation(s)
- Bartosz Caban
- Faculty of Biology and Environmental Protection, Department of Neurobiology; University of Lodz; Lodz Poland
| | - Agata Staszelis
- Faculty of Biology and Environmental Protection, Department of Neurobiology; University of Lodz; Lodz Poland
| | - Paulina Kazmierska
- Faculty of Biology and Environmental Protection, Department of Neurobiology; University of Lodz; Lodz Poland
| | - Tomasz Kowalczyk
- Faculty of Biology and Environmental Protection, Department of Neurobiology; University of Lodz; Lodz Poland
| | - Jan Konopacki
- Faculty of Biology and Environmental Protection, Department of Neurobiology; University of Lodz; Lodz Poland
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Ruan M, Young CK, McNaughton N. Bi-Directional Theta Modulation between the Septo-Hippocampal System and the Mammillary Area in Free-Moving Rats. Front Neural Circuits 2017; 11:62. [PMID: 28955209 PMCID: PMC5600904 DOI: 10.3389/fncir.2017.00062] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 08/25/2017] [Indexed: 01/07/2023] Open
Abstract
Hippocampal (HPC) theta oscillations have long been linked to various functions of the brain. Many cortical and subcortical areas that also exhibit theta oscillations have been linked to functional circuits with the hippocampus on the basis of coupled activities at theta frequencies. We examine, in freely moving rats, the characteristics of diencephalic theta local field potentials (LFPs) recorded in the supramammillary/mammillary (SuM/MM) areas that are bi-directionally connected to the HPC through the septal complex. Using partial directed coherence (PDC), we find support for previous suggestions that SuM modulates HPC theta at higher frequencies. We find weak separation of SuM and MM by dominant theta frequency recorded locally. Contrary to oscillatory cell activities under anesthesia where SuM is insensitive, but MM is sensitive to medial septal (MS) inactivation, theta LFPs persisted and became indistinguishable after MS-inactivation. However, MS-inactivation attenuated SuM/MM theta power, while increasing the frequency of SuM/MM theta. MS-inactivation also reduced root mean squared power in both HPC and SuM/MM equally, but reduced theta power differentially in the time domain. We provide converging evidence that SuM is preferentially involved in coding HPC theta at higher frequencies, and that the MS-HPC circuit normally imposes a frequency-limiting modulation over the SuM/MM area as suggested by cell-based recordings in anesthetized animals. In addition, we provide evidence that the postulated SuM-MS-HPC-MM circuit is under complex bi-directional control, rather than SuM and MM having roles as unidirectional relays in the network.
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Affiliation(s)
- Ming Ruan
- Department of Psychology and Brain Health Research Centre, University of OtagoDunedin, New Zealand.,Department of Pediatrics and Neonatal Services, Zhuhai Municipal Women's and Children's HospitalGuangdong, China
| | - Calvin K Young
- Department of Psychology and Brain Health Research Centre, University of OtagoDunedin, New Zealand
| | - Neil McNaughton
- Department of Psychology and Brain Health Research Centre, University of OtagoDunedin, New Zealand
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Matsumoto N, Okamoto K, Takagi Y, Ikegaya Y. 3-Hz subthreshold oscillations of CA2 neurons In vivo. Hippocampus 2016; 26:1570-1578. [PMID: 27650674 DOI: 10.1002/hipo.22657] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2016] [Indexed: 12/12/2022]
Abstract
The CA2 region is unique in the hippocampus; it receives direct synaptic innervations from several hypothalamic nuclei and expresses various receptors of neuromodulators, including adenosine, vasopressin, and oxytocin. Furthermore, the CA2 region may have distinct brain functions, such as the control of instinctive and social behaviors; however, little is known about the dynamics of the subthreshold membrane potentials of CA2 neurons in vivo. We conducted whole-cell current-clamp recordings from CA2 pyramidal cells in urethane-anesthetized mice and monitored the intrinsic fluctuations in their membrane potentials. The CA2 pyramidal cells emitted spontaneous action potentials at mean firing rates of ∼0.8 Hz. In approximately half of the neurons, the subthreshold membrane potential oscillated at ∼3 Hz. In two neurons, we obtained simultaneous recordings of local field potentials from the CA1 stratum radiatum and demonstrated that the 3-Hz oscillations of CA2 neurons were not correlated with CA1 field potentials. In tetrodotoxin-perfused acute hippocampal slices, the membrane potentials of CA2 pyramidal cells were not preferentially entrained to 3-Hz sinusoidal current inputs, which suggest that intracellular 3-Hz oscillations reflect the neuronal dynamics of the surrounding networks. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Nobuyoshi Matsumoto
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Kazuki Okamoto
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yuki Takagi
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.,Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita City, Osaka, Japan
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Bocian R, Kłos-Wojtczak P, Konopacki J. Cell discharge correlates of posterior hypothalamic theta rhythm. Recipe for success in recording stable field potential. Brain Res 2016; 1646:551-559. [PMID: 27353451 DOI: 10.1016/j.brainres.2016.06.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 06/21/2016] [Accepted: 06/24/2016] [Indexed: 02/08/2023]
Abstract
The theta rhythm discovered in the posterior hypothalamus area (PHa) differs from theta observed in the hippocampal formation. In comparison to hippocampal spontaneous theta, the theta recorded in the PHa is rarely registered, has lower amplitude, often disappears, and sometimes returns after a few minutes. These features indicate that spontaneous theta recorded in the PHa is not an appropriate experimental model to search for the correlation between PHa cell discharges and local field potential. In this paper we present standard experimental conditions necessary to record theta-related cells in the PHa in anesthetized rats. Three pharmacological agents were used in the experiments to induce PHa theta rhythm in urethanized rats: carbachol (CCH), carbenoxolone and kainic acid, which are potent enough to induce well-synchronized PHa theta. However, CCH was found to be the best pharmacological tool to induce PHa theta oscillations, due to its longest duration of action and lack of preliminary epileptogenic effects. It seems that CCH-induced theta can be the most suitable pharmacological model for experiments with the use of protocol of long-lasting recordings of PHa theta-related cell discharges.
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Affiliation(s)
- Renata Bocian
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland.
| | - Paulina Kłos-Wojtczak
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland.
| | - Jan Konopacki
- Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland.
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12
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Bocian R, Caban B, Kłos-Wojtczak P, Konopacki J, Kowalczyk T. Is electrical coupling involved in the generation of posterior hypothalamic theta rhythm? Eur J Neurosci 2016; 44:2324-33. [DOI: 10.1111/ejn.13338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 07/06/2016] [Accepted: 07/13/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Renata Bocian
- Department of Neurobiology; Faculty of Biology and Environmental Protection; University of Lodz; Pomorska Str. No 141/143 90-236 Lodz Poland
| | - Bartosz Caban
- Department of Neurobiology; Faculty of Biology and Environmental Protection; University of Lodz; Pomorska Str. No 141/143 90-236 Lodz Poland
| | - Paulina Kłos-Wojtczak
- Department of Neurobiology; Faculty of Biology and Environmental Protection; University of Lodz; Pomorska Str. No 141/143 90-236 Lodz Poland
| | - Jan Konopacki
- Department of Neurobiology; Faculty of Biology and Environmental Protection; University of Lodz; Pomorska Str. No 141/143 90-236 Lodz Poland
| | - Tomasz Kowalczyk
- Department of Neurobiology; Faculty of Biology and Environmental Protection; University of Lodz; Pomorska Str. No 141/143 90-236 Lodz Poland
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13
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Bocian R, Kłos-Wojtczak P, Caban B, Kowalczyk T, Kaźmierska P, Konopacki J. Cell discharge correlates of posterior hypothalamic theta rhythm recorded in anesthetized rats and brain slices. Hippocampus 2016; 26:1354-69. [DOI: 10.1002/hipo.22612] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 02/05/2023]
Affiliation(s)
- Renata Bocian
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
| | - Paulina Kłos-Wojtczak
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
| | - Bartosz Caban
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
| | - Tomasz Kowalczyk
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
| | - Paulina Kaźmierska
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
| | - Jan Konopacki
- Department of Neurobiology; the University of Łódź; Pomorska Str. No 141/143 Łódź 91-236 Poland
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NMDA-glutamatergic activation of the ventral tegmental area induces hippocampal theta rhythm in anesthetized rats. Brain Res Bull 2014; 107:43-53. [PMID: 24915630 DOI: 10.1016/j.brainresbull.2014.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 05/20/2014] [Accepted: 06/02/2014] [Indexed: 01/07/2023]
Abstract
Glutamate afferents reaching the ventral tegmental area (VTA) affect dopamine (DA) cells in this structure probably mainly via NMDA receptors. VTA appears to be one of the structures involved in regulation of hippocampal theta rhythm, and this work aimed at assessing the role of glutamatergic activation of the VTA in the theta regulation. Male Wistar rats (n=17) were divided into groups, each receiving intra-VTA microinjection (0.5 μl) of either solvent (water), glutamatergic NMDA agonist (0.2 μg) or antagonist (MK-801, 3.0 μg). Changes in local field potential were assessed on the basis of peak power (Pmax) and corresponding peak frequency (Fmax) for the delta (0.5-3 Hz) and theta (3-6 Hz) bands. NMDA microinjection evoked long-lasting hippocampal theta. The rhythm appeared with a latency of ca. 12 min post-injection and lasted for over 30 min; Pmax in this band was significantly increased for 50 min, while simultaneously Pmax in the delta band remained lower than in control conditions. Theta Fmax and delta Fmax were increased in almost entire post-injection period (by 0.3-0.5 Hz and 0.3-0.7 Hz, respectively). MK-801 depressed the sensory-evoked theta: tail pinch could not induce theta for 30 min after the injection; Pmax significantly decreased in the theta band and at the same time it increased in the delta band. Theta Fmax decreased 10 and 20 min post injection (by 0.4-0.5 Hz) and delta Fmax decreased in almost entire post injection period (by 0.3-0.7 Hz). NMDA injection generates theta rhythm probably through stimulation of dopaminergic activity within the VTA.
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