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Gil-Miravet I, Núñez-Molina Á, Navarro-Sánchez M, Castillo-Gómez E, Ros-Bernal F, Gundlach AL, Olucha-Bordonau FE. Nucleus incertus projections to rat medial septum and entorhinal cortex: rare collateralization and septal-gating of temporal lobe theta rhythm activity. Brain Struct Funct 2023:10.1007/s00429-023-02650-x. [PMID: 37173580 DOI: 10.1007/s00429-023-02650-x] [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: 12/24/2022] [Accepted: 05/04/2023] [Indexed: 05/15/2023]
Abstract
Nucleus incertus (NI) neurons in the pontine tegmentum give rise to ascending forebrain projections and express the neuropeptide relaxin-3 (RLN3) which acts via the relaxin-family peptide 3 receptor (RXFP3). Activity in the hippocampus and entorhinal cortex can be driven from the medial septum (MS), and the NI projects to all these centers, where a prominent pattern of activity is theta rhythm, which is related to spatial memory processing. Therefore, we examined the degree of collateralization of NI projections to the MS and the medial temporal lobe (MTL), comprising medial and lateral entorhinal cortex (MEnt, LEnt) and dentate gyrus (DG), and the ability of the MS to drive entorhinal theta in the adult rat. We injected fluorogold and cholera toxin-B into the MS septum and either MEnt, LEnt or DG, to determine the percentage of retrogradely labeled neurons in the NI projecting to both or single targets, and the relative proportion of these neurons that were RLN3-positive ( +). The projection to the MS was threefold stronger than that to the MTL. Moreover, a majority of NI neurons projected independently to either MS or the MTL. However, RLN3 + neurons collateralize significantly more than RLN3-negative (-) neurons. In in vivo studies, electrical stimulation of the NI induced theta activity in the MS and the entorhinal cortex, which was impaired by intraseptal infusion of an RXFP3 antagonist, R3(BΔ23-27)R/I5, particularly at ~ 20 min post-injection. These findings suggest that the MS plays an important relay function in the NI-induced generation of theta within the entorhinal cortex.
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Grants
- POSDOC/2021/19 Universitat Jaume I
- PREDOC/2021/19 Universitat Jaume I
- UJI-A2017-17 Universitat Jaume I
- POSDOC/2021/19 Universitat Jaume I
- PID2019-107809RB-I00 Ministerio de Ciencia, Innovación y Universidades
- RTI2018-095698-B-I00 Ministerio de Ciencia, Innovación y Universidades
- RTI2018-095698-B-I00 Ministerio de Ciencia, Innovación y Universidades
- RTI2018-095698-B-I00 Ministerio de Ciencia, Innovación y Universidades
- 19I436 Fundación Alicia Koplowitz
- 19I436 Fundación Alicia Koplowitz
- 19I436 Fundación Alicia Koplowitz
- AICO/2021/246 Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana
- AICO/2021/246 Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana
- AICO/2021/246 Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana
- 1067522 National Health and Medical Research Council
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Affiliation(s)
- Isis Gil-Miravet
- Departamento de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I, CIBERSAM-ISCIII, S/N 12071, Castellón de la Plana, Spain
| | - Ángel Núñez-Molina
- Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Mónica Navarro-Sánchez
- Departamento de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I, CIBERSAM-ISCIII, S/N 12071, Castellón de la Plana, Spain
| | - Esther Castillo-Gómez
- Departamento de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I, CIBERSAM-ISCIII, S/N 12071, Castellón de la Plana, Spain
| | - Francisco Ros-Bernal
- Departamento de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I, CIBERSAM-ISCIII, S/N 12071, Castellón de la Plana, Spain
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, Florey Department of Neuroscience and Mental Health and Department of Anatomy and Physiology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Francisco E Olucha-Bordonau
- Departamento de Medicina, Facultad de Ciencias de la Salud, Universitat Jaume I, CIBERSAM-ISCIII, S/N 12071, Castellón de la Plana, Spain.
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2
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Pena RFO, Rotstein HG. The voltage and spiking responses of subthreshold resonant neurons to structured and fluctuating inputs: persistence and loss of resonance and variability. BIOLOGICAL CYBERNETICS 2022; 116:163-190. [PMID: 35038010 DOI: 10.1007/s00422-021-00919-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
We systematically investigate the response of neurons to oscillatory currents and synaptic-like inputs and we extend our investigation to non-structured synaptic-like spiking inputs with more realistic distributions of presynaptic spike times. We use two types of chirp-like inputs consisting of (i) a sequence of cycles with discretely increasing frequencies over time, and (ii) a sequence having the same cycles arranged in an arbitrary order. We develop and use a number of frequency-dependent voltage response metrics to capture the different aspects of the voltage response, including the standard impedance (Z) and the peak-to-trough amplitude envelope ([Formula: see text]) profiles. We show that Z-resonant cells (cells that exhibit subthreshold resonance in response to sinusoidal inputs) also show [Formula: see text]-resonance in response to sinusoidal inputs, but generally do not (or do it very mildly) in response to square-wave and synaptic-like inputs. In the latter cases the resonant response using Z is not predictive of the preferred frequencies at which the neurons spike when the input amplitude is increased above subthreshold levels. We also show that responses to conductance-based synaptic-like inputs are attenuated as compared to the response to current-based synaptic-like inputs, thus providing an explanation to previous experimental results. These response patterns were strongly dependent on the intrinsic properties of the participating neurons, in particular whether the unperturbed Z-resonant cells had a stable node or a focus. In addition, we show that variability emerges in response to chirp-like inputs with arbitrarily ordered patterns where all signals (trials) in a given protocol have the same frequency content and the only source of uncertainty is the subset of all possible permutations of cycles chosen for a given protocol. This variability is the result of the multiple different ways in which the autonomous transient dynamics is activated across cycles in each signal (different cycle orderings) and across trials. We extend our results to include high-rate Poisson distributed current- and conductance-based synaptic inputs and compare them with similar results using additive Gaussian white noise. We show that the responses to both Poisson-distributed synaptic inputs are attenuated with respect to the responses to Gaussian white noise. For cells that exhibit oscillatory responses to Gaussian white noise (band-pass filters), the response to conductance-based synaptic inputs are low-pass filters, while the response to current-based synaptic inputs may remain band-pass filters, consistent with experimental findings. Our results shed light on the mechanisms of communication of oscillatory activity among neurons in a network via subthreshold oscillations and resonance and the generation of network resonance.
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Affiliation(s)
- Rodrigo F O Pena
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, Newark, USA
| | - Horacio G Rotstein
- Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University, Newark, USA.
- Corresponding Investigator, CONICET, Buenos Aires, Argentina.
- Graduate Faculty, Behavioral Neurosciences Program, Rutgers University, Newark, USA.
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3
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Nuñez A, Buño W. The Theta Rhythm of the Hippocampus: From Neuronal and Circuit Mechanisms to Behavior. Front Cell Neurosci 2021; 15:649262. [PMID: 33746716 PMCID: PMC7970048 DOI: 10.3389/fncel.2021.649262] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 01/28/2021] [Indexed: 11/17/2022] Open
Abstract
This review focuses on the neuronal and circuit mechanisms involved in the generation of the theta (θ) rhythm and of its participation in behavior. Data have accumulated indicating that θ arises from interactions between medial septum-diagonal band of Broca (MS-DbB) and intra-hippocampal circuits. The intrinsic properties of MS-DbB and hippocampal neurons have also been shown to play a key role in θ generation. A growing number of studies suggest that θ may represent a timing mechanism to temporally organize movement sequences, memory encoding, or planned trajectories for spatial navigation. To accomplish those functions, θ and gamma (γ) oscillations interact during the awake state and REM sleep, which are considered to be critical for learning and memory processes. Further, we discuss that the loss of this interaction is at the base of various neurophatological conditions.
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Affiliation(s)
- Angel Nuñez
- Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autonoma de Madrid, Madrid, Spain
| | - Washington Buño
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
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4
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Olajide OJ, Suvanto ME, Chapman CA. Molecular mechanisms of neurodegeneration in the entorhinal cortex that underlie its selective vulnerability during the pathogenesis of Alzheimer's disease. Biol Open 2021; 10:bio056796. [PMID: 33495355 PMCID: PMC7860115 DOI: 10.1242/bio.056796] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The entorhinal cortex (EC) is a vital component of the medial temporal lobe, and its contributions to cognitive processes and memory formation are supported through its extensive interconnections with the hippocampal formation. During the pathogenesis of Alzheimer's disease (AD), many of the earliest degenerative changes are seen within the EC. Neurodegeneration in the EC and hippocampus during AD has been clearly linked to impairments in memory and cognitive function, and a growing body of evidence indicates that molecular and functional neurodegeneration within the EC may play a primary role in cognitive decline in the early phases of AD. Defining the mechanisms underlying molecular neurodegeneration in the EC is crucial to determining its contributions to the pathogenesis of AD. Surprisingly few studies have focused on understanding the mechanisms of molecular neurodegeneration and selective vulnerability within the EC. However, there have been advancements indicating that early dysregulation of cellular and molecular signaling pathways in the EC involve neurodegenerative cascades including oxidative stress, neuroinflammation, glia activation, stress kinases activation, and neuronal loss. Dysfunction within the EC can impact the function of the hippocampus, which relies on entorhinal inputs, and further degeneration within the hippocampus can compound this effect, leading to severe cognitive disruption. This review assesses the molecular and cellular mechanisms underlying early degeneration in the EC during AD. These mechanisms may underlie the selective vulnerability of neuronal subpopulations in this brain region to the disease development and contribute both directly and indirectly to cognitive loss.This paper has an associated Future Leader to Watch interview with the first author of the article.
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Affiliation(s)
- Olayemi Joseph Olajide
- Division of Neurobiology, Department of Anatomy, University of Ilorin, Ilorin, Nigeria, PMB 1515
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montréal, Québec, Canada H4B 1R6
| | - Marcus E Suvanto
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montréal, Québec, Canada H4B 1R6
| | - Clifton Andrew Chapman
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montréal, Québec, Canada H4B 1R6
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5
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Hernández-Pérez JJ, Cooper KW, Newman EL. Medial entorhinal cortex activates in a traveling wave in the rat. eLife 2020; 9:52289. [PMID: 32057292 PMCID: PMC7046467 DOI: 10.7554/elife.52289] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 02/04/2020] [Indexed: 12/12/2022] Open
Abstract
Traveling waves are hypothesized to support the long-range coordination of anatomically distributed circuits. Whether separate strongly interacting circuits exhibit traveling waves remains unknown. The hippocampus exhibits traveling ‘theta’ waves and interacts strongly with the medial entorhinal cortex (MEC). To determine whether the MEC also activates in a traveling wave, we performed extracellular recordings of local field potentials (LFP) and multi-unit activity along the MEC. These recordings revealed progressive phase shifts in activity, indicating that the MEC also activates in a traveling wave. Variation in theta waveform along the region, generated by gradients in local physiology, contributed to the observed phase shifts. Removing waveform-related phase shifts left significant residual phase shifts. The residual phase shifts covaried with theta frequency in a manner consistent with those generated by weakly coupled oscillators. These results show that the coordination of anatomically distributed circuits could be enabled by traveling waves but reveal heterogeneity in the mechanisms generating those waves.
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Affiliation(s)
- J Jesús Hernández-Pérez
- Department of Psychological and Brain Sciences, Indiana University Bloomington, Bloomington, United States
| | - Keiland W Cooper
- Department of Psychological and Brain Sciences, Indiana University Bloomington, Bloomington, United States
| | - Ehren L Newman
- Department of Psychological and Brain Sciences, Indiana University Bloomington, Bloomington, United States
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6
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Yuan H, Shou G, Gleghorn D, Ding L, Cha YH. Resting State Functional Connectivity Signature of Treatment Effects of Repetitive Transcranial Magnetic Stimulation in Mal de Debarquement Syndrome. Brain Connect 2018; 7:617-626. [PMID: 28967282 PMCID: PMC5695731 DOI: 10.1089/brain.2017.0514] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) has been used in experimental protocols to treat mal de debarquement syndrome (MdDS), a neurological condition that represents a maladaptive brain state resulting from entrainment to external oscillating motion. Medical treatments and biomarkers for MdDS remain limited but neuromodulation with rTMS has shown evidence for therapeutic effects. This study took a neuroimaging approach to examine the neuromodulatory effect of rTMS on MdDS. Twenty individuals with MdDS underwent five daily treatments of rTMS over bilateral dorsolateral prefrontal cortex (DLPFC). Participants received 1 Hz over right DLPFC (1200 pulses) followed by 10 Hz over left DLPFC (2000 pulses). Resting state functional magnetic resonance imaging was acquired before and after treatments to determine functional connectivity changes associated with a positive treatment effect. A single-subject-based analysis protocol was developed to capture the degree of resting state functional connectivity (RSFC) between the rTMS target and the entorhinal cortex (EC), an area previously shown to be hypermetabolic in MdDS. Our results showed that rocking motion perception in subjects was modulated by rTMS over the DLPFC. Improvements in symptoms correlated most strongly with a post-rTMS reduction in functional connectivity between the left EC and the precuneus, right inferior parietal lobule, and the contralateral EC, which are part of the posterior default mode network. Positive response to rTMS correlated with higher baseline RSFC between the DLPFC and the EC. Our findings suggest that baseline prefrontal-limbic functional connectivity may serve as a predictor of treatment response to prefrontal stimulation in MdDS and that RSFC may serve as a dynamic biomarker of symptom status.
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Affiliation(s)
- Han Yuan
- 1 Stephenson School of Biomedical Engineering, University of Oklahoma , Norman, Oklahoma.,2 Laureate Institute for Brain Research , Tulsa, Oklahoma
| | - Guofa Shou
- 1 Stephenson School of Biomedical Engineering, University of Oklahoma , Norman, Oklahoma
| | | | - Lei Ding
- 1 Stephenson School of Biomedical Engineering, University of Oklahoma , Norman, Oklahoma.,2 Laureate Institute for Brain Research , Tulsa, Oklahoma
| | - Yoon-Hee Cha
- 2 Laureate Institute for Brain Research , Tulsa, Oklahoma
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7
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Cha YH, Shou G, Gleghorn D, Doudican BC, Yuan H, Ding L. Electrophysiological Signatures of Intrinsic Functional Connectivity Related to rTMS Treatment for Mal de Debarquement Syndrome. Brain Topogr 2018; 31:1047-1058. [PMID: 30099627 PMCID: PMC6182441 DOI: 10.1007/s10548-018-0671-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 08/07/2018] [Indexed: 01/02/2023]
Abstract
To determine intrinsic functional connectivity (IFC) related to symptom changes induced by rTMS in mal de debarquement syndrome (MdDS), a motion perceptual disorder induced by entrainment to oscillating motion. Twenty right-handed women (mean age: 52.9 ± 12.6 years; mean duration illness: 35.2 ± 24.2 months) with MdDS received five sessions of rTMS (1 Hz right DLPFC, 10 Hz left DLPFC) over consecutive days. High-density (128-channel) resting-state EEG were recorded prior to and following treatment sessions and analyzed using a group-level independent component (IC) analysis. IFC between 19 ICs was quantified by inter-IC phase coherence (ICPC) in six frequency bands (delta, theta, low alpha, high alpha, beta, gamma). Correlational analyses between IFCs and symptoms were performed. Symptom improvement after rTMS was significantly correlated with (1) an increase in low alpha band (8–10 Hz) IFC but a decrease of IFC in all other bands, and (2) high baseline IFC in the high alpha (11–13 Hz) and beta bands (14–30 Hz). Most treatment related IFC changes occurred between frontal and parietal regions with a linear association between the degree of symptom improvement and the number of coherent IFC changes. Frequency band and region specific IFC changes correlate with and can predict symptom changes induced by rTMS over DLPFC in MdDS. MdDS symptom response correlates with high baseline IFC in most frequency bands. Treatment induced increase in long-range low alpha IFC and decreases in IFC in other bands as well as the proportion of coherent IFC changes correlate with symptom reduction.
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Affiliation(s)
- Yoon-Hee Cha
- Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK, 74136, USA. .,University of Tulsa, Tulsa, OK, USA.
| | - Guofa Shou
- Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA
| | - Diamond Gleghorn
- Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK, 74136, USA
| | - Benjamin C Doudican
- Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK, 74136, USA
| | - Han Yuan
- Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK, 74136, USA.,Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA.,Institute for Biomedical Engineering, Science and Technology, University of Oklahoma, Norman, OK, USA
| | - Lei Ding
- Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK, 74136, USA.,Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA.,Institute for Biomedical Engineering, Science and Technology, University of Oklahoma, Norman, OK, USA
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8
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Double-Blind Sham-Controlled Crossover Trial of Repetitive Transcranial Magnetic Stimulation for Mal de Debarquement Syndrome. Otol Neurotol 2017; 37:805-12. [PMID: 27176615 DOI: 10.1097/mao.0000000000001045] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE To determine whether the chronic rocking dizziness that occurs in Mal de Debarquement Syndrome (MdDS) can be suppressed with repetitive transcranial magnetic stimulation (rTMS) beyond the treatment period. METHODS We performed a prospective randomized double-blind sham controlled crossover trial of 5-days of rTMS utilizing high frequency (10 Hz) stimulation over the left dorsolateral prefrontal cortex (DLPFC). RESULTS Eight right-handed women (44.5 [SD 7.0] yr) with classical motion-triggered MdDS (mean duration 42.1 [SD 13.2] mo) participated. Group level mixed effects repeated measures analysis of variance (ANOVA) showed improvement in our primary outcome measure, the Dizziness Handicap Inventory (DHI) at Post TMS Weeks 1, 3, and 4 (p < 0.05) and a trend at Week 2 (p = 0.089) after Real rTMS. On the Hospital Anxiety and Depression Scale (HADS), improvements started at Post TMS Week 2 for the Anxiety subscore and Post TMS Week 3 for the Depression subscore after Real rTMS only (p < 0.05). There were no group level improvements on the MdDS Balance Rating Scale (MBRS) after Real rTMS though there were three participants who improved on an individual level. There were no significant group level changes after Sham stimulation on any measure. CONCLUSION Our study provides evidence that the dizziness, mood and anxiety symptoms of MdDS can be improved with 10 Hz rTMS over left DLPFC beyond the treatment period in selected individuals. rTMS may be a useful adjunctive treatment for the management of chronic rocking dizziness in individuals with MdDS but treatment durations longer than 5 days or maintenance treatment are likely needed for sustained symptom suppression.
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9
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V-Ghaffari B, Kouhnavard M, Elbasiouny SM. Mixed-mode oscillations in pyramidal neurons under antiepileptic drug conditions. PLoS One 2017; 12:e0178244. [PMID: 28591171 PMCID: PMC5462370 DOI: 10.1371/journal.pone.0178244] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 05/10/2017] [Indexed: 11/19/2022] Open
Abstract
Subthreshold oscillations in combination with large-amplitude oscillations generate mixed-mode oscillations (MMOs), which mediate various spatial and temporal cognition and memory processes and behavioral motor tasks. Although many studies have shown that canard theory is a reliable method to investigate the properties underlying the MMOs phenomena, the relationship between the results obtained by applying canard theory and conductance-based models of neurons and their electrophysiological mechanisms are still not well understood. The goal of this study was to apply canard theory to the conductance-based model of pyramidal neurons in layer V of the Entorhinal Cortex to investigate the properties of MMOs under antiepileptic drug conditions (i.e., when persistent sodium current is inhibited). We investigated not only the mathematical properties of MMOs in these neurons, but also the electrophysiological mechanisms that shape spike clustering. Our results show that pyramidal neurons can display two types of MMOs and the magnitude of the slow potassium current determines whether MMOs of type I or type II would emerge. Our results also indicate that slow potassium currents with large time constant have significant impact on generating the MMOs, as opposed to fast inward currents. Our results provide complete characterization of the subthreshold activities in MMOs in pyramidal neurons and provide explanation to experimental studies that showed MMOs of type I or type II in pyramidal neurons under antiepileptic drug conditions.
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Affiliation(s)
- Babak V-Ghaffari
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science & Mathematics, Wright State University, Dayton, Ohio, United States of America
- * E-mail: (SME); (BV)
| | - M. Kouhnavard
- Malaysia-Japan Int. Inst. of Tech, University Technology Malaysia, Kuala Lumpur, Malaysia
| | - Sherif M. Elbasiouny
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science & Mathematics, Wright State University, Dayton, Ohio, United States of America
- Department of Biomedical, Industrial and Human Factors Engineering, College of Engineering & Computer Science, Wright State University, Dayton, Ohio, United States of America
- * E-mail: (SME); (BV)
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10
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Rotstein HG. The shaping of intrinsic membrane potential oscillations: positive/negative feedback, ionic resonance/amplification, nonlinearities and time scales. J Comput Neurosci 2016; 42:133-166. [PMID: 27909841 DOI: 10.1007/s10827-016-0632-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 11/07/2016] [Accepted: 11/10/2016] [Indexed: 12/26/2022]
Abstract
The generation of intrinsic subthreshold (membrane potential) oscillations (STOs) in neuronal models requires the interaction between two processes: a relatively fast positive feedback that favors changes in voltage and a slower negative feedback that opposes these changes. These are provided by the so-called resonant and amplifying gating variables associated to the participating ionic currents. We investigate both the biophysical and dynamic mechanisms of generation of STOs and how their attributes (frequency and amplitude) depend on the model parameters for biophysical (conductance-based) models having qualitatively different types of resonant currents (activating and inactivating) and an amplifying current. Combinations of the same types of ionic currents (same models) in different parameter regimes give rise to different types of nonlinearities in the voltage equation: quasi-linear, parabolic-like and cubic-like. On the other hand, combinations of different types of ionic currents (different models) may give rise to the same type of nonlinearities. We examine how the attributes of the resulting STOs depend on the combined effect of these resonant and amplifying ionic processes, operating at different effective time scales, and the various types of nonlinearities. We find that, while some STO properties and attribute dependencies on the model parameters are determined by the specific combinations of ionic currents (biophysical properties), and are different for models with different such combinations, others are determined by the type of nonlinearities and are common for models with different types of ionic currents. Our results highlight the richness of STO behavior in single cells as the result of the various ways in which resonant and amplifying currents interact and affect the generation and termination of STOs as control parameters change. We make predictions that can be tested experimentally and are expected to contribute to the understanding of how rhythmic activity in neuronal networks emerge from the interplay of the intrinsic properties of the participating neurons and the network connectivity.
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Affiliation(s)
- Horacio G Rotstein
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, 07102, USA.
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11
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Bertram R, Rubin JE. Multi-timescale systems and fast-slow analysis. Math Biosci 2016; 287:105-121. [PMID: 27424950 DOI: 10.1016/j.mbs.2016.07.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 07/01/2016] [Accepted: 07/10/2016] [Indexed: 11/28/2022]
Abstract
Mathematical models of biological systems often have components that vary on different timescales. This multi-timescale character can lead to problems when doing computer simulations, which can require a great deal of computer time so that the components that change on the fastest time scale can be resolved. Mathematical analysis of these multi-timescale systems can be greatly simplified by partitioning them into subsystems that evolve on different time scales. The subsystems are then analyzed semi-independently, using a technique called fast-slow analysis. In this review we describe the fast-slow analysis technique and apply it to relaxation oscillations, neuronal bursting oscillations, canard oscillations, and mixed-mode oscillations. Although these examples all involve neural systems, the technique can and has been applied to other biological, chemical, and physical systems. It is a powerful analysis method that will become even more useful in the future as new experimental techniques push forward the complexity of biological models.
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Affiliation(s)
- Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics Florida State University, Florida State University, Tallahassee, FL, United States.
| | - Jonathan E Rubin
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, United States
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12
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Shilnikov AL, Maurer AP. The Art of Grid Fields: Geometry of Neuronal Time. Front Neural Circuits 2016; 10:12. [PMID: 27013981 PMCID: PMC4782041 DOI: 10.3389/fncir.2016.00012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 02/19/2016] [Indexed: 11/13/2022] Open
Abstract
The discovery of grid cells in the entorhinal cortex has both elucidated our understanding of spatial representations in the brain, and germinated a large number of theoretical models regarding the mechanisms of these cells' striking spatial firing characteristics. These models cross multiple neurobiological levels that include intrinsic membrane resonance, dendritic integration, after hyperpolarization characteristics and attractor dynamics. Despite the breadth of the models, to our knowledge, parallels can be drawn between grid fields and other temporal dynamics observed in nature, much of which was described by Art Winfree and colleagues long before the initial description of grid fields. Using theoretical and mathematical investigations of oscillators, in a wide array of mediums far from the neurobiology of grid cells, Art Winfree has provided a substantial amount of research with significant and profound similarities. These theories provide specific inferences into the biological mechanisms and extraordinary resemblances across phenomenon. Therefore, this manuscript provides a novel interpretation on the phenomenon of grid fields, from the perspective of coupled oscillators, postulating that grid fields are the spatial representation of phase resetting curves in the brain. In contrast to prior models of gird cells, the current manuscript provides a sketch by which a small network of neurons, each with oscillatory components can operate to form grid cells, perhaps providing a unique hybrid between the competing attractor neural network and oscillatory interference models. The intention of this new interpretation of the data is to encourage novel testable hypotheses.
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Affiliation(s)
- Andrey L. Shilnikov
- Neuroscience Institute and Department of Mathematics and Statistics, Georgia State UniversityAtlanta, GA, USA
- Institute for Information Technology, Mathematics and Mechanics, Lobachevsky State University of Nizhni NovgorodNizhni Novgorod, Russia
| | - Andrew Porter Maurer
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of FloridaGainesville, FL, USA
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Stepan J, Hladky F, Uribe A, Holsboer F, Schmidt MV, Eder M. High-Speed imaging reveals opposing effects of chronic stress and antidepressants on neuronal activity propagation through the hippocampal trisynaptic circuit. Front Neural Circuits 2015; 9:70. [PMID: 26594153 PMCID: PMC4635222 DOI: 10.3389/fncir.2015.00070] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 10/22/2015] [Indexed: 12/11/2022] Open
Abstract
Antidepressants (ADs) are used as first-line treatment for most stress-related psychiatric disorders. The alterations in brain circuit dynamics that can arise from stress exposure and underlie therapeutic actions of ADs remain, however, poorly understood. Here, enabled by a recently developed voltage-sensitive dye imaging (VSDI) assay in mouse brain slices, we examined the impact of chronic stress and concentration-dependent effects of eight clinically used ADs (belonging to different chemical/functional classes) on evoked neuronal activity propagations through the hippocampal trisynaptic circuitry (HTC: perforant path → dentate gyrus (DG) → area CA3 → area CA1). Exposure of mice to chronic social defeat stress led to markedly weakened activity propagations (“HTC-Waves”). In contrast, at concentrations in the low micromolar range, all ADs, which were bath applied to slices, caused an amplification of HTC-Waves in CA regions (invariably in area CA1). The fast-acting “antidepressant” ketamine, the mood stabilizer lithium, and brain-derived neurotrophic factor (BDNF) exerted comparable enhancing effects, whereas the antipsychotic haloperidol and the anxiolytic diazepam attenuated HTC-Waves. Collectively, we provide direct experimental evidence that chronic stress can depress neuronal signal flow through the HTC and demonstrate shared opposing effects of ADs. Thus, our study points to a circuit-level mechanism of ADs to counteract stress-induced impairment of hippocampal network function. However, the observed effects of ADs are impossible to depend on enhanced neurogenesis.
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Affiliation(s)
- Jens Stepan
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany ; Clinical Department, Max Planck Institute of Psychiatry Munich, Germany
| | - Florian Hladky
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany
| | - Andrés Uribe
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Research Group "Stress Resilience", Max Planck Institute of Psychiatry Munich, Germany
| | - Florian Holsboer
- Max Planck Institute of Psychiatry Munich, Germany ; HMNC GmbH Munich, Germany
| | - Mathias V Schmidt
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Research Group "Stress Resilience", Max Planck Institute of Psychiatry Munich, Germany
| | - Matthias Eder
- Max Planck Institute of Psychiatry Munich, Germany ; Department Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry Munich, Germany ; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of Psychiatry Munich, Germany
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14
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Abbasi S, Kumar SS. Layer-specific modulation of entorhinal cortical excitability by presubiculum in a rat model of temporal lobe epilepsy. J Neurophysiol 2015; 114:2854-66. [PMID: 26378210 DOI: 10.1152/jn.00823.2015] [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: 08/24/2015] [Accepted: 09/09/2015] [Indexed: 11/22/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is the most common form of epilepsy in adults and is often refractory to antiepileptic medications. The medial entorhinal area (MEA) is affected in TLE but mechanisms underlying hyperexcitability of MEA neurons require further elucidation. Previous studies suggest that inputs from the presubiculum (PrS) contribute to MEA pathophysiology. We assessed electrophysiologically how PrS influences MEA excitability using the rat pilocarpine model of TLE. PrS-MEA connectivity was confirmed by electrically stimulating PrS afferents while recording from neurons within superficial layers of MEA. Assessment of alterations in PrS-mediated synaptic drive to MEA neurons was made following focal application of either glutamate or NBQX to the PrS in control and epileptic animals. Here, we report that monosynaptic inputs to MEA from PrS neurons are conserved in epileptic rats, and that PrS modulation of MEA excitability is layer-specific. PrS contributes more to synaptic inhibition of LII stellate cells than excitation. Under epileptic conditions, stellate cell inhibition is significantly reduced while excitatory synaptic drive is maintained at levels similar to control. PrS contributes to both synaptic excitation and inhibition of LIII pyramidal cells in control animals. Under epileptic conditions, overall excitatory synaptic drive to these neurons is enhanced while inhibitory synaptic drive is maintained at control levels. Additionally, neither glutamate nor NBQX applied focally to PrS now affected EPSC and IPSC frequency of LIII pyramidal neurons. These layer-specific changes in PrS-MEA interactions are unexpected and of significance in unraveling pathophysiological mechanisms underlying TLE.
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Affiliation(s)
- Saad Abbasi
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University, Tallahassee, Florida
| | - Sanjay S Kumar
- Department of Biomedical Sciences, College of Medicine and Program in Neuroscience, Florida State University, Tallahassee, Florida
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15
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Rotstein HG. Subthreshold amplitude and phase resonance in models of quadratic type: nonlinear effects generated by the interplay of resonant and amplifying currents. J Comput Neurosci 2015; 38:325-54. [PMID: 25586875 DOI: 10.1007/s10827-014-0544-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 10/29/2014] [Accepted: 12/10/2014] [Indexed: 01/23/2023]
Abstract
We investigate the biophysical and dynamic mechanisms of generation of subthreshold amplitude and phase resonance in response to sinusoidal input currents in two-dimensional models of quadratic type. These models feature a parabolic voltage nullcline and a linear nullcline for the recovery gating variable, capturing the interplay of the so-called resonant currents (e.g., hyperpolarization-activated mixed-cation inward and slow potassium) and amplifying currents (e.g., persistent sodium) in biophysically realistic parameter regimes. These currents underlie the generation of resonance in medial entorhinal cortex layer II stellate cells and CA1 pyramidal cells. We show that quadratic models exhibit nonlinear amplifications of the voltage response to sinusoidal inputs in the resonant frequency band. These are expressed as an increase in the impedance profile as the input amplitude increases. They are stronger for values positive than negative to resting potential and are accompanied by a shift in the phase profile, a decrease in the resonant and phase-resonant frequencies, and an increase in the sharpness of the voltage response. These effects are more prominent for smaller values of ∊ (larger levels of the time scale separation between the voltage and the resonant gating variable) and for values of the resting potential closer to threshold for spike generation. All other parameter fixed, as ∊ increases the voltage response becomes "more linear"; i.e., the nonlinearities are present, but "ignored". In addition, the nonlinear effects are strongly modulated by the curvature of the parabolic voltage nullcline (partially reflecting the effects of the amplifying current) and the slope of the resonant current activation curve. Following the effects of changes in the biophysical conductances of realistic conductance-based models through the parameters of the quadratic model, we characterize the qualitatively different effects that resonant and amplifying currents have on the nonlinear properties of the voltage response. We identify different classes of resonant currents, represented by h- and slow potassium, according to whether they enhance (h-) or attenuate (slow potassium) the nonlinear effects. Finally, we use dynamical systems tools to investigate the dynamic mechanisms of generation of resonance and phase-resonance. We show that the nonlinear effects on the voltage response (e.g., amplification of the voltage response in the resonant frequency band and shifts in the resonant and phase-resonant frequencies) result from the ability of limit cycle trajectories to follow the unstable (right) branch of the voltage nullcline for a significant amount of time. This is a canard-related mechanism that has been shown to underlie the generation of intrinsic subthreshold oscillations in quadratic type models such as medial entorhinal cortex stellate cells. Overall, our results highlight the complexity of the voltage response to oscillatory inputs in nonlinear models and the roles that resonant and amplifying currents have in shaping these responses.
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Affiliation(s)
- Horacio G Rotstein
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ, 07102, USA,
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16
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Gervais NJ, Barrett-Bernstein M, Sutherland RJ, Mumby DG. Retrograde and anterograde memory following selective damage to the dorsolateral entorhinal cortex. Neurobiol Learn Mem 2014; 116:14-26. [PMID: 25108197 DOI: 10.1016/j.nlm.2014.07.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 07/08/2014] [Accepted: 07/31/2014] [Indexed: 11/25/2022]
Abstract
Anatomical and electrophysiological evidence suggest the dorsolateral entorhinal cortex (DLEC) is involved in processing spatial information, but there is currently no consensus on whether its functions are necessary for normal spatial learning and memory. The present study examined the effects of excitotoxic lesions of the DLEC on retrograde and anterograde memory on two tests of allocentric spatial learning: a hidden fixed-platform watermaze task, and a novelty-preference-based dry-maze test. Deficits were observed on both tests when training occurred prior to but not following n-methyl d-aspartate (NMDA) lesions of DLEC, suggesting retrograde memory impairment in the absence of anterograde impairments for the same information. The retrograde memory impairments were temporally-graded; rats that received DLEC lesions 1-3 days following training displayed deficits, while those that received lesions 7-10 days following training performed like a control group that received sham surgery. The deficits were not attenuated by co-infusion of tetrodotoxin, suggesting they are not due to disruption of neural processing in structures efferent to the DLEC, such as the hippocampus. The present findings provide evidence that the DLEC is involved in the consolidation of allocentric spatial information.
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Affiliation(s)
- Nicole J Gervais
- Center for Studies in Behavioral Neurobiology (CSBN), Department of Psychology, Concordia University, 7141 Sherbrooke Street West (SP-244), Montreal, Quebec H4B 1R6, Canada.
| | - Meagan Barrett-Bernstein
- Center for Studies in Behavioral Neurobiology (CSBN), Department of Psychology, Concordia University, 7141 Sherbrooke Street West (SP-244), Montreal, Quebec H4B 1R6, Canada.
| | - Robert J Sutherland
- Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
| | - Dave G Mumby
- Center for Studies in Behavioral Neurobiology (CSBN), Department of Psychology, Concordia University, 7141 Sherbrooke Street West (SP-244), Montreal, Quebec H4B 1R6, Canada.
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17
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Bayesian integration of information in hippocampal place cells. PLoS One 2014; 9:e89762. [PMID: 24603429 PMCID: PMC3945610 DOI: 10.1371/journal.pone.0089762] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 01/24/2014] [Indexed: 11/29/2022] Open
Abstract
Accurate spatial localization requires a mechanism that corrects for errors, which might arise from inaccurate sensory information or neuronal noise. In this paper, we propose that Hippocampal place cells might implement such an error correction mechanism by integrating different sources of information in an approximately Bayes-optimal fashion. We compare the predictions of our model with physiological data from rats. Our results suggest that useful predictions regarding the firing fields of place cells can be made based on a single underlying principle, Bayesian cue integration, and that such predictions are possible using a remarkably small number of model parameters.
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18
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Greenhill SD, Chamberlain SEL, Lench A, Massey PV, Yuill KH, Woodhall GL, Jones RSG. Background synaptic activity in rat entorhinal cortex shows a progressively greater dominance of inhibition over excitation from deep to superficial layers. PLoS One 2014; 9:e85125. [PMID: 24454801 PMCID: PMC3893176 DOI: 10.1371/journal.pone.0085125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 11/22/2013] [Indexed: 11/21/2022] Open
Abstract
The entorhinal cortex (EC) controls hippocampal input and output, playing major roles in memory and spatial navigation. Different layers of the EC subserve different functions and a number of studies have compared properties of neurones across layers. We have studied synaptic inhibition and excitation in EC neurones, and we have previously compared spontaneous synaptic release of glutamate and GABA using patch clamp recordings of synaptic currents in principal neurones of layers II (L2) and V (L5). Here, we add comparative studies in layer III (L3). Such studies essentially look at neuronal activity from a presynaptic viewpoint. To correlate this with the postsynaptic consequences of spontaneous transmitter release, we have determined global postsynaptic conductances mediated by the two transmitters, using a method to estimate conductances from membrane potential fluctuations. We have previously presented some of this data for L3 and now extend to L2 and L5. Inhibition dominates excitation in all layers but the ratio follows a clear rank order (highest to lowest) of L2>L3>L5. The variance of the background conductances was markedly higher for excitation and inhibition in L2 compared to L3 or L5. We also show that induction of synchronized network epileptiform activity by blockade of GABA inhibition reveals a relative reluctance of L2 to participate in such activity. This was associated with maintenance of a dominant background inhibition in L2, whereas in L3 and L5 the absolute level of inhibition fell below that of excitation, coincident with the appearance of synchronized discharges. Further experiments identified potential roles for competition for bicuculline by ambient GABA at the GABAA receptor, and strychnine-sensitive glycine receptors in residual inhibition in L2. We discuss our results in terms of control of excitability in neuronal subpopulations of EC neurones and what these may suggest for their functional roles.
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Affiliation(s)
- Stuart David Greenhill
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | | | - Alex Lench
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Peter Vernon Massey
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Kathryn Heather Yuill
- School of Biomedical & Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, United Kingdom
| | - Gavin Lawrence Woodhall
- Aston Brain Centre, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
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19
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Barrett SG, Chapman CA. Contribution of muscarinic M1 receptors to the cholinergic suppression of synaptic responses in layer II of the entorhinal cortex. Neurosci Lett 2013; 554:11-5. [DOI: 10.1016/j.neulet.2013.08.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Revised: 08/23/2013] [Accepted: 08/25/2013] [Indexed: 11/24/2022]
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20
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Boehlen A, Henneberger C, Heinemann U, Erchova I. Contribution of near-threshold currents to intrinsic oscillatory activity in rat medial entorhinal cortex layer II stellate cells. J Neurophysiol 2012; 109:445-63. [PMID: 23076110 DOI: 10.1152/jn.00743.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The temporal lobe is well known for its oscillatory activity associated with exploration, navigation, and learning. Intrinsic membrane potential oscillations (MPOs) and resonance of stellate cells (SCs) in layer II of the entorhinal cortex are thought to contribute to network oscillations and thereby to the encoding of spatial information. Generation of both MPOs and resonance relies on the expression of specific voltage-dependent ion currents such as the hyperpolarization-activated cation current (I(H)), the persistent sodium current (I(NaP)), and the noninactivating muscarine-modulated potassium current (I(M)). However, the differential contributions of these currents remain a matter of debate. We therefore examined how they modify neuronal excitability near threshold and generation of near-threshold MPOs and resonance in vitro. We found that resonance mainly relied on I(H) and was reduced by I(H) blockers and modulated by cAMP and an I(M) enhancer but that neither of the currents exhibited full control over MPOs in these cells. As previously reported, I(H) controlled a theta-frequency component of MPOs such that blockade of I(H) resulted in fewer regular oscillations that retained low-frequency components and high peak amplitude. However, pharmacological inhibition and augmentation of I(M) also affected MPO frequencies and amplitudes. In contrast to other cell types, inhibition of I(NaP) did not result in suppression of MPOs but only in a moderation of their properties. We reproduced the experimentally observed effects in a single-compartment stochastic model of SCs, providing further insight into the interactions between different ionic conductances.
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Affiliation(s)
- Anne Boehlen
- Institute of Neurophysiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
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21
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Heys JG, Schultheiss NW, Shay CF, Tsuno Y, Hasselmo ME. Effects of acetylcholine on neuronal properties in entorhinal cortex. Front Behav Neurosci 2012; 6:32. [PMID: 22837741 PMCID: PMC3402879 DOI: 10.3389/fnbeh.2012.00032] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Accepted: 06/07/2012] [Indexed: 11/13/2022] Open
Abstract
The entorhinal cortex (EC) receives prominent cholinergic innervation from the medial septum and the vertical limb of the diagonal band of Broca (MSDB). To understand how cholinergic neurotransmission can modulate behavior, research has been directed toward identification of the specific cellular mechanisms in EC that can be modulated through cholinergic activity. This review focuses on intrinsic cellular properties of neurons in EC that may underlie functions such as working memory, spatial processing, and episodic memory. In particular, the study of stellate cells (SCs) in medial entorhinal has resulted in discovery of correlations between physiological properties of these neurons and properties of the unique spatial representation that is demonstrated through unit recordings of neurons in medial entorhinal cortex (mEC) from awake-behaving animals. A separate line of investigation has demonstrated persistent firing behavior among neurons in EC that is enhanced by cholinergic activity and could underlie working memory. There is also evidence that acetylcholine plays a role in modulation of synaptic transmission that could also enhance mnemonic function in EC. Finally, the local circuits of EC demonstrate a variety of interneuron physiology, which is also subject to cholinergic modulation. Together these effects alter the dynamics of EC to underlie the functional role of acetylcholine in memory.
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Affiliation(s)
- James G. Heys
- Graduate Program for Neuroscience, Center for Memory and Brain, Boston UniversityBoston, MA, USA
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22
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Pilli J, Abbasi S, Richardson M, Kumar SS. Diversity and excitability of deep-layer entorhinal cortical neurons in a model of temporal lobe epilepsy. J Neurophysiol 2012; 108:1724-38. [PMID: 22745466 DOI: 10.1152/jn.00364.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The entorhinal cortex (ERC) is critically implicated in temporal lobe epileptogenesis--the most common type of adult epilepsy. Previous studies have suggested that epileptiform discharges likely initiate in seizure-sensitive deep layers (V-VI) of the medial entorhinal area (MEA) and propagate into seizure-resistant superficial layers (II-III) and hippocampus, establishing a lamina-specific distinction between activities of deep- versus superficial-layer neurons and their seizure susceptibilities. While layer II stellate cells in MEA have been shown to be hyperexcitable and hypersynchronous in patients and animal models of temporal lobe epilepsy (TLE), the fate of neurons in the deep layers under epileptic conditions and their overall contribution to epileptogenicity of this region have remained unclear. We used whole cell recordings from slices of the ERC in normal and pilocarpine-treated epileptic rats to characterize the electrophysiological properties of neurons in this region and directly assess changes in their excitatory and inhibitory synaptic drive under epileptic conditions. We found a surprising heterogeneity with at least three major types and two subtypes of functionally distinct excitatory neurons. However, contrary to expectation, none of the major neuron types characterized showed any significant changes in their excitability, barring loss of excitatory and inhibitory inputs in a subtype of neurons whose dendrite extended into layer III, where neurons are preferentially lost during TLE. We confirmed hyperexcitability of layer II neurons in the same slices, suggesting minimal influence of deep-layer input on superficial-layer neuron excitability under epileptic conditions. These data show that deep layers of ERC contain a more diverse population of excitatory neurons than previously envisaged that appear to belie their seizure-sensitive reputation.
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Affiliation(s)
- Jyotsna Pilli
- Dept. of Biomedical Sciences, College of Medicine, Florida State Univ., 1115 West Call St., Tallahassee, FL 32306-4300, USA
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23
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ValdéS-Cruz AL, Negrete-DíAZ JV, Magdaleno-Madrigal VM, MartíNez-Vargas D, FernáNdez-Mas R, AlmazáN-Alvarado S, Torres-GarcÍA ME, Flores G. Electroencephalographic activity in neonatal ventral hippocampus lesion in adult rats. Synapse 2012; 66:738-46. [DOI: 10.1002/syn.21563] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 03/28/2012] [Indexed: 12/31/2022]
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24
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Pastoll H, Ramsden HL, Nolan MF. Intrinsic electrophysiological properties of entorhinal cortex stellate cells and their contribution to grid cell firing fields. Front Neural Circuits 2012; 6:17. [PMID: 22536175 PMCID: PMC3334835 DOI: 10.3389/fncir.2012.00017] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Accepted: 03/25/2012] [Indexed: 11/21/2022] Open
Abstract
The medial entorhinal cortex (MEC) is an increasingly important focus for investigation of mechanisms for spatial representation. Grid cells found in layer II of the MEC are likely to be stellate cells, which form a major projection to the dentate gyrus. Entorhinal stellate cells are distinguished by distinct intrinsic electrophysiological properties, but how these properties contribute to representation of space is not yet clear. Here, we review the ionic conductances, synaptic, and excitable properties of stellate cells, and examine their implications for models of grid firing fields. We discuss why existing data are inconsistent with models of grid fields that require stellate cells to generate periodic oscillations. An alternative possibility is that the intrinsic electrophysiological properties of stellate cells are tuned specifically to control integration of synaptic input. We highlight recent evidence that the dorsal-ventral organization of synaptic integration by stellate cells, through differences in currents mediated by HCN and leak potassium channels, influences the corresponding organization of grid fields. Because accurate cellular data will be important for distinguishing mechanisms for generation of grid fields, we introduce new data comparing properties measured with whole-cell and perforated patch-clamp recordings. We find that clustered patterns of action potential firing and the action potential after-hyperpolarization (AHP) are particularly sensitive to recording condition. Nevertheless, with both methods, these properties, resting membrane properties and resonance follow a dorsal-ventral organization. Further investigation of the molecular basis for synaptic integration by stellate cells will be important for understanding mechanisms for generation of grid fields.
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Affiliation(s)
- Hugh Pastoll
- Neuroinformatics Doctoral Training Centre, University of Edinburgh Edinburgh, UK
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25
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Kuehn C. On decomposing mixed-mode oscillations and their return maps. CHAOS (WOODBURY, N.Y.) 2011; 21:033107. [PMID: 21974642 DOI: 10.1063/1.3615231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Alternating patterns of small and large amplitude oscillations occur in a wide variety of physical, chemical, biological, and engineering systems. These mixed-mode oscillations (MMOs) are often found in systems with multiple time scales. Previous differential equation modeling and analysis of MMOs have mainly focused on local mechanisms to explain the small oscillations. Numerical continuation studies reported different MMO patterns based on parameter variation. This paper aims at improving the link between local analysis and numerical simulation. Our starting point is a numerical study of a singular return map for the Koper model which is a prototypical example for MMOs, which also relates to local normal form theory. We demonstrate that many MMO patterns can be understood geometrically by approximating the singular maps with affine and quadratic maps. Motivated by our numerical analysis we use abstract affine and quadratic return map models in combination with two local normal forms that generate small oscillations. Using this decomposition approach we can reproduce many classical MMO patterns and effectively decouple bifurcation parameters for local and global parts of the flow. The overall strategy we employ provides an alternative technique for understanding MMOs.
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Affiliation(s)
- Christian Kuehn
- Max Planck Institute for the Physics of Complex Systems, Noethnitzer St. 38-Dresden, Saxony 01187, Germany
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26
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Koenig J, Linder AN, Leutgeb JK, Leutgeb S. The Spatial Periodicity of Grid Cells Is Not Sustained During Reduced Theta Oscillations. Science 2011; 332:592-5. [DOI: 10.1126/science.1201685] [Citation(s) in RCA: 314] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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27
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Cappaert NLM, Lopes da Silva FH, Wadman WJ. Spatio-temporal dynamics of theta oscillations in hippocampal-entorhinal slices. Hippocampus 2010; 19:1065-77. [PMID: 19338021 DOI: 10.1002/hipo.20570] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Theta oscillations (4-12 Hz) are associated with learning and memory and are found in the hippocampus and the entorhinal cortex (EC). The spatio-temporal organization of rhythmic activity in the hippocampal-EC complex was investigated in vitro. The voltage sensitive absorption dye NK3630 was used to record the changes in aggregated membrane voltage simultaneously from the neuronal networks involved. Oscillatory activity at 7.0 Hz (range, 5.8-8.2) was induced in the slice with the muscarinic agonist carbachol (75-100 microM) in the presence of bicuculline (5 microM). Time relations between all recording sites were analyzed using cross-correlation functions which revealed systematic phase shifts in the theta oscillation recorded from the different entorhinal and hippocampal subregions. These phase shifts could be interpreted as propagation delays. The oscillation propagates over the slice in a characteristic spatio-temporal sequence, where the entorhinal cortex leads, followed by the subiculum and then the dentate gyrus (DG), to finally reach the CA3 and the CA1 area. The delay from dentate gyrus to the CA3 area was 12.4 +/- 1.1 ms (mean +/- s.e.m.) and from the CA3 to the CA1 region it was 10.9 +/- 1.9 ms. The propagation delays between the hippocampal subregions resemble the latencies of electrically evoked responses in the same subregions. Removing the entorhinal cortex from the slice changed the spatiotemporal pattern into a more clustered pattern with higher local synchrony. We conclude that in the slice, carbachol-induced theta oscillations are initiated in the entorhinal cortex. The EC could serve to control the information flow through the neuronal network in the subregions of the hippocampus by synchronizing and/or entraining their responses to external inputs.
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Affiliation(s)
- N L M Cappaert
- SILS - Center for NeuroScience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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28
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Wójtowicz AM, van den Boom L, Chakrabarty A, Maggio N, Haq RU, Behrens CJ, Heinemann U. Monoamines block kainate- and carbachol-induced gamma-oscillations but augment stimulus-induced gamma-oscillations in rat hippocampus in vitro. Hippocampus 2009; 19:273-88. [PMID: 19173289 DOI: 10.1002/hipo.20508] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Monoamines are implicated in a cognitive processes in a variety of brain regions, including the hippocampal formation, where storage and retrieval of information are facilitated by synchronous network activities. We have investigated the effects of norepinephrine, serotonin, and dopamine on carbachol-, kainate-, and stimulus-induced hippocampal gamma-oscillations employing combined extra- and intracellular recordings. Monoamines dose-dependently and reversibly suppressed kainate- and carbachol-induced gamma-oscillations while increasing the frequency. The effect of serotonin was mimicked by fenfluramine, which releases serotonin from presynaptic terminals. Forskolin also suppressed kainate- and carbachol-induced gamma-oscillations. This effect was mimicked by 8-Br-cAMP and isoproterenol, an agonist of noradrenergic beta-receptor suggesting that the monoamines-mediated suppression of these oscillations could involve intracellular cyclic adenosine 3',5'-cyclic monophosphate (AMP). By contrast, stimulus-induced gamma-oscillations were dose-dependently augmented in power and duration after monoamines application. Intracellular recordings from pyramidal cells revealed that monoamines prolonged the stimulus-induced depolarization and membrane potential oscillations. Stimulus-induced gamma-oscillations were also suppressed by isoproterenol, the D1 agonist SKF-38393 forskolin, and 8-Br-cAMP. This suggests that the augmentation of stimulus-induced gamma-oscillations by monoamines involves--at least in part-different classes of cells than in case of carbachol- and kainate-induced gamma-oscillations.
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Affiliation(s)
- Anna Maria Wójtowicz
- Department of Neurobiology, Johannes Müller-Center for Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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Beed PS, Salmen B, Schmitz D. GluK2-mediated excitability within the superficial layers of the entorhinal cortex. PLoS One 2009; 4:e5576. [PMID: 19440371 PMCID: PMC2679203 DOI: 10.1371/journal.pone.0005576] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 04/13/2009] [Indexed: 11/18/2022] Open
Abstract
Recent analysis of genetically modified mice deficient in different kainate receptor (KAR) subunits have strongly pointed to a role of the GluK2 subunit, mediating the vulnerability of the brain towards seizures. Research concerning this issue has focused mainly on the hippocampus. However, several studies point to a potential role of other parts of the hippocampal formation, in particular the entorhinal cortex, in the development of epileptic seizures. There is extensive cell death after such seizures in layer III of the medial entorhinal cortex (LIII mEC), making this region of special interest for investigation into related pathological conditions. We therefore characterized KAR mediated currents in LIII mEC pyramidal neurons by several different approaches. Using patch-clamp technique, in combination with glutamate uncaging in horizontal brain slices, we show that LIII mEC neurons exhibit KAR currents. Use of genetically modified mice reveal that these currents are mediated by GluK2 containing KARs. The IV curve indicates the predominant presence of a Ca2+ impermeable and edited form of the KAR. Finally, we show that GluK2 containing kainate receptors are essential for kainate-induced gamma oscillations within the entorhinal cortex.
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Affiliation(s)
- Prateep S. Beed
- NeuroScience Research Center, Charité, Universitätsmedizin Berlin, Berlin, Germany
| | - Benedikt Salmen
- NeuroScience Research Center, Charité, Universitätsmedizin Berlin, Berlin, Germany
| | - Dietmar Schmitz
- NeuroScience Research Center, Charité, Universitätsmedizin Berlin, Berlin, Germany
- * E-mail:
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30
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Dudman JT, Nolan MF. Stochastically gating ion channels enable patterned spike firing through activity-dependent modulation of spike probability. PLoS Comput Biol 2009; 5:e1000290. [PMID: 19214199 PMCID: PMC2631146 DOI: 10.1371/journal.pcbi.1000290] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 01/06/2009] [Indexed: 11/19/2022] Open
Abstract
The transformation of synaptic input into patterns of spike output is a fundamental operation that is determined by the particular complement of ion channels that a neuron expresses. Although it is well established that individual ion channel proteins make stochastic transitions between conducting and non-conducting states, most models of synaptic integration are deterministic, and relatively little is known about the functional consequences of interactions between stochastically gating ion channels. Here, we show that a model of stellate neurons from layer II of the medial entorhinal cortex implemented with either stochastic or deterministically gating ion channels can reproduce the resting membrane properties of stellate neurons, but only the stochastic version of the model can fully account for perithreshold membrane potential fluctuations and clustered patterns of spike output that are recorded from stellate neurons during depolarized states. We demonstrate that the stochastic model implements an example of a general mechanism for patterning of neuronal output through activity-dependent changes in the probability of spike firing. Unlike deterministic mechanisms that generate spike patterns through slow changes in the state of model parameters, this general stochastic mechanism does not require retention of information beyond the duration of a single spike and its associated afterhyperpolarization. Instead, clustered patterns of spikes emerge in the stochastic model of stellate neurons as a result of a transient increase in firing probability driven by activation of HCN channels during recovery from the spike afterhyperpolarization. Using this model, we infer conditions in which stochastic ion channel gating may influence firing patterns in vivo and predict consequences of modifications of HCN channel function for in vivo firing patterns.
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Affiliation(s)
- Joshua T Dudman
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America.
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31
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Dynamic cross-frequency couplings of local field potential oscillations in rat striatum and hippocampus during performance of a T-maze task. Proc Natl Acad Sci U S A 2008; 105:20517-22. [PMID: 19074268 DOI: 10.1073/pnas.0810524105] [Citation(s) in RCA: 534] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oscillatory rhythms in different frequency ranges mark different behavioral states and are thought to provide distinct temporal windows that coherently bind cooperating neuronal assemblies. However, the rhythms in different bands can also interact with each other, suggesting the possibility of higher-order representations of brain states by such rhythmic activity. To explore this possibility, we analyzed local field potential oscillations recorded simultaneously from the striatum and the hippocampus. As rats performed a task requiring active navigation and decision making, the amplitudes of multiple high-frequency oscillations were dynamically modulated in task-dependent patterns by the phase of cooccurring theta-band oscillations both within and across these structures, particularly during decision-making behavioral epochs. Moreover, the modulation patterns uncovered distinctions among both high- and low-frequency subbands. Cross-frequency coupling of multiple neuronal rhythms could be a general mechanism used by the brain to perform network-level dynamical computations underlying voluntary behavior.
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Burton BG, Economo MN, Lee GJ, White JA. Development of theta rhythmicity in entorhinal stellate cells of the juvenile rat. J Neurophysiol 2008; 100:3144-57. [PMID: 18829850 DOI: 10.1152/jn.90424.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mature stellate cells of the rat medial entorhinal cortex (EC), layer II, exhibit subthreshold membrane potential oscillations (MPOs) at theta frequencies (4-12 Hz) in vitro. We find that MPOs appear between postnatal days 14 (P14) and 18 (P18) but show little further change by day 28+ (P28-P32). To identify the factors responsible, we examined the electrical responses of developing stellate cells, paying attention to two currents thought necessary for mature oscillation: the h current I(h), which provides the slow rectification required for resonance; and a persistent sodium current I(NaP), which provides amplification of resonance. Responses to injected current revealed that P14 cells were often nonresonant with a relatively high resistance. Densities of I(h) and I(NaP) both rose by about 50% from P14 to P18. However, I(h) levels fell to intermediate values by P28+. Given the nonrobust trend in I(h) expression and a previously demonstrated potency of even low levels of I(h) to sustain oscillation, we propose that resonance and MPOs are limited at P14 more by low levels of I(NaP) than of I(h). The relative importance of I(NaP) for the development of MPOs is supported by simulations of a conductance-based model, which also suggest that general shunt conductance may influence the precise age when MPOs appear. In addition to our physiological study, we analyzed spine densities at P14, P18, and P28+ and found a vigorous synaptogenesis across the whole period. Our data predict that functions that rely on theta rhythmicity in the hippocampal network are limited until at least P18.
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Affiliation(s)
- Brian G Burton
- Department of Biomedical Engineering, Center for Memory and Brain, Center for BioDynamics, Boston University, Boston, Massachusetts, USA
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Johnston D, Narayanan R. Active dendrites: colorful wings of the mysterious butterflies. Trends Neurosci 2008; 31:309-16. [PMID: 18471907 DOI: 10.1016/j.tins.2008.03.004] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 03/18/2008] [Accepted: 03/25/2008] [Indexed: 02/02/2023]
Abstract
Santiago Ramón y Cajal had referred to neurons as the 'mysterious butterflies of the soul.' Wings of these butterflies--their dendrites--were traditionally considered as passive integrators of synaptic information. Owing to a growing body of experimental evidence, it is now widely accepted that these wings are colorful, endowed with a plethora of active conductances, with each family of these butterflies made of distinct hues and shades. Furthermore, rapidly evolving recent literature also provides direct and indirect demonstrations for activity-dependent plasticity of these active conductances, pointing toward chameleonic adaptability in these hues. These experimental findings firmly establish the immense computational power of a single neuron, and thus constitute a turning point toward the understanding of various aspects of neuronal information processing. In this brief historical perspective, we track important milestones in the chameleonic transmogrification of these mysterious butterflies.
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Affiliation(s)
- Daniel Johnston
- Center for Learning and Memory, The University of Texas at Austin, Austin, TX 78712, USA.
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34
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Erchova I, McGonigle DJ. Rhythms of the brain: an examination of mixed mode oscillation approaches to the analysis of neurophysiological data. CHAOS (WOODBURY, N.Y.) 2008; 18:015115. [PMID: 18377096 DOI: 10.1063/1.2900015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In the nervous system many behaviorally relevant dynamical processes are characterized by episodes of complex oscillatory states, whose periodicity may be expressed over multiple temporal and spatial scales. In at least some of these instances the variability in oscillatory amplitude and frequency can be explained in terms of deterministic dynamics, rather than being purely noise-driven. Recently interest has increased in studying the application of mixed-mode oscillations (MMOs) to neurophysiological data. MMOs are complex periodic waveforms where each period is comprised of several maxima and minima of different amplitudes. While MMOs might be expected to occur in brain kinetics, only a few examples have been identified thus far. In this article, we review recent theoretical and experimental findings on brain oscillatory rhythms in relation to MMOs, focusing on examples at the single neuron level but also briefly touching on possible instances of the phenomenon across local and global brain networks.
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Affiliation(s)
- Irina Erchova
- Institute for Adaptive and Neural Computation, School of Informatics and Centre of Neuroscience Research, University of Edinburgh, 5 Forrest Hill Road, Edinburgh EH1 2QL, United Kingdom
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Solinas S, Forti L, Cesana E, Mapelli J, De Schutter E, D'Angelo E. Computational reconstruction of pacemaking and intrinsic electroresponsiveness in cerebellar Golgi cells. Front Cell Neurosci 2007; 1:2. [PMID: 18946520 PMCID: PMC2525930 DOI: 10.3389/neuro.03.002.2007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 12/07/2007] [Indexed: 11/17/2022] Open
Abstract
The Golgi cells have been recently shown to beat regularly in vitro (Forti et al., 2006. J. Physiol. 574, 711–729). Four main currents were shown to be involved, namely a persistent sodium current (INa-p), an h current (Ih), an SK-type calcium-dependent potassium current (IK-AHP), and a slow M-like potassium current (IK-slow). These ionic currents could take part, together with others, also to different aspects of neuronal excitability like responses to depolarizing and hyperpolarizing current injection. However, the ionic mechanisms and their interactions remained largely hypothetical. In this work, we have investigated the mechanisms of Golgi cell excitability by developing a computational model. The model predicts that pacemaking is sustained by subthreshold oscillations tightly coupled to spikes. INa-p and IK-slow emerged as the critical determinants of oscillations. Ih also played a role by setting the oscillatory mechanism into the appropriate membrane potential range. IK-AHP, though taking part to the oscillation, appeared primarily involved in regulating the ISI following spikes. The combination with other currents, in particular a resurgent sodium current (INa-r) and an A-current (IK-A), allowed a precise regulation of response frequency and delay. These results provide a coherent reconstruction of the ionic mechanisms determining Golgi cell intrinsic electroresponsiveness and suggests important implications for cerebellar signal processing, which will be fully developed in a companion paper (Solinas et al., 2008. Front. Neurosci. 2:4).
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Affiliation(s)
- Sergio Solinas
- Department of Cellular and Molecular Physiological and Pharmacological Sciences, University of Pavia and CNISM Italy
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Wolansky T, Pagliardini S, Greer JJ, Dickson CT. Immunohistochemical characterization of substance P receptor (NK(1)R)-expressing interneurons in the entorhinal cortex. J Comp Neurol 2007; 502:427-41. [PMID: 17366610 DOI: 10.1002/cne.21338] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It has been reported that application of substance P (SP) to the medial portion of the entorhinal cortex (EC) induces a powerful antiepileptic effect (Maubach et al. [1998] Neuroscience 83:1047-1062). This effect is presumably mediated via inhibitory interneurons expressing the neurokinin-1 receptor (NK(1)R), but the existence of NK(1)R-expressing inhibitory interneurons in the EC has not yet been reported. The present immunohistochemical study was performed in the rat to examine the existence and distribution of NK(1)R-expressing neurons in the EC as well as any co-expression of other neurotransmitters/neuromodulators known to be associated with inhibitory interneurons: gamma-aminobutyric acid (GABA), parvalbumin (PARV), calretinin (CT), calbindin (CB), somatostatin (SST), and neuropeptide Y (NPY). Our results indicated that NK(1)R-positive neurons were distributed rather sparsely (especially in the medial EC), primarily in layers II, V, and VI. The results of our double-immunohistochemical staining indicated that the vast majority of NK(1)R-expressing neurons also expressed GABA, SST, and NPY. In addition, CT was co-expressed in a weakly stained subgroup of NK(1)R-expressing neurons, and CB was co-expressed very rarely in the lateral EC, but not in the medial EC. In contrast, SP-immunopositive axons with fine varicosities were distributed diffusely throughout all layers of the EC, appearing to radiate from the angular bundle. SP may be released in a paracrine manner to activate a group of NK(1)R-expressing entorhinal neurons that co-express GABA, SST, and NPY, exerting a profound inhibitory influence on synchronized network activity in the EC.
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Affiliation(s)
- Trish Wolansky
- Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada T6G 2R3
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37
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West PJ, Dalpé-Charron A, Wilcox KS. Differential contribution of kainate receptors to excitatory postsynaptic currents in superficial layer neurons of the rat medial entorhinal cortex. Neuroscience 2007; 146:1000-12. [PMID: 17395391 PMCID: PMC2921318 DOI: 10.1016/j.neuroscience.2007.02.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 02/02/2007] [Accepted: 02/19/2007] [Indexed: 02/02/2023]
Abstract
Although in situ hybridization studies have revealed the presence of kainate receptor (KAR) mRNA in neurons of the rat medial entorhinal cortex (mEC), the functional presence and roles of these receptors are only beginning to be examined. To address this deficiency, whole cell voltage clamp recordings of locally evoked excitatory postsynaptic currents (EPSCs) were made from mEC layer II and III neurons in combined entorhinal cortex-hippocampal brain slices. Three types of neurons were identified by their electroresponsive membrane properties, locations, and morphologies: stellate-like "Sag" neurons in layer II (S), pyramidal-like "No Sag" neurons in layer III (NS), and "Intermediate Sag" neurons with varied morphologies and locations (IS). Non-NMDA EPSCs in these neurons were composed of two components, and the slow decay component in NS neurons had larger amplitudes and contributed more to the combined EPSC than did those observed in S and IS neurons. This slow component was mediated by KARs and was characterized by its resistance to either 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI 52466, 100 microM) or 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[lsqb]f[rsqb]quinoxaline-7-sulfonamide (NBQX, 1 microM), relatively slow decay kinetics, and sensitivity to 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10-50 microM). KAR-mediated EPSCs in pyramidal-like NS neurons contributed significantly more to the combined non-NMDA EPSC than did those from S and IS neurons. Layer III neurons of the mEC are selectively susceptible to degeneration in human temporal lobe epilepsy (TLE) and animal models of TLE such as kainate-induced status epilepticus. Characterizing differences in the complement of postsynaptic receptors expressed in injury prone versus injury resistant mEC neurons represents an important step toward understanding the vulnerability of layer III neurons seen in TLE.
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Affiliation(s)
- P J West
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
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Hamam BN, Sinai M, Poirier G, Chapman CA. Cholinergic suppression of excitatory synaptic responses in layer II of the medial entorhinal cortex. Hippocampus 2007; 17:103-13. [PMID: 17146776 DOI: 10.1002/hipo.20249] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Theta-frequency (4-12 Hz) electroencephalographic activity is thought to play a role in mechanisms mediating sensory and mnemonic processing in the entorhinal cortex and hippocampus, but the effects of acetylcholine on excitatory synaptic inputs to the entorhinal cortex are not well understood. Field excitatory postsynaptic potentials (fEPSPs) evoked by stimulation of the piriform (olfactory) cortex were recorded in the medial entorhinal cortex during behaviors associated with theta activity (active mobility) and were compared with those recorded during nontheta behaviors (awake immobility and slow wave sleep). Synaptic responses were smaller during behavioral activity than during awake immobility and sleep, and responses recorded during movement were largest during the negative phase of the theta rhythm. Systemic administration of cholinergic agonists reduced the amplitude of fEPSPs, and the muscarinic receptor blocker scopolamine strongly enhanced fEPSPs, suggesting that the theta-related suppression of fEPSPs is mediated in part by cholinergic inputs. The reduction in fEPSPs was investigated using in vitro intracellular recordings of EPSPs in Layer II neurons evoked by stimulation of Layer I afferents. Constant bath application of the muscarinic agonist carbachol depolarized membrane potential and suppressed EPSP amplitude in Layer II neurons. The suppression of EPSPs was not associated with a substantial change in input resistance, and could not be accounted for by a depolarization-induced reduction in driving force on the EPSP. The GABA(A) receptor-blocker bicuculline (50 microM) did not prevent the cholinergic suppression of EPSPs, suggesting that the suppression is not dependent on inhibitory mechanisms. Paired-pulse facilitation of field and intracellular EPSPs were enhanced by carbachol, indicating that the suppression is likely due to inhibition of presynaptic glutamate release. These results indicate that, in addition to well known effects on postsynaptic conductances that increase cellular excitability, cholinergic activation in the entorhinal cortex results in a strong reduction in strength of excitatory synaptic inputs from the piriform cortex.
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Affiliation(s)
- Bassam N Hamam
- Department of Psychology, Concordia University, Montréal, Québec, Canada
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39
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Ma L, Shalinsky MH, Alonso A, Dickson CT. Effects of serotonin on the intrinsic membrane properties of layer II medial entorhinal cortex neurons. Hippocampus 2007; 17:114-29. [PMID: 17146777 DOI: 10.1002/hipo.20250] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although serotonin (5-HT) is an important neuromodulator in the superficial layers of the medial entorhinal cortex (mEC), there is some disagreement concerning its influences upon the membrane properties of neurons within this region. We performed whole cell recordings of mEC Layer II projection neurons in rat brain slices in order to characterize the intrinsic influences of 5-HT. In current clamp, 5-HT evoked a biphasic response consisting of a moderately short latency and large amplitude hyperpolarization followed by a slowly developing, long lasting, and small amplitude depolarization. Correspondingly, in voltage clamp, 5-HT evoked a robust outward followed by a smaller inward shift of holding current. The outward current evoked by 5-HT showed a consistent current/voltage (I/V) relationship across cells with inward rectification, and demonstrating a reversal potential that was systematically dependent upon the extracellular concentration of K(+), suggesting that it was predominantly carried by potassium ions. However, the inward current showed a less consistent I/V relationship across different cells, suggesting multiple independent ionic mechanisms. The outward current was mediated through activation of 5-HT(1A) receptors via a G-protein dependent mechanism while inward currents were evoked in a 5-HT(1A)-independent fashion. A significant proportion of the inward current was blocked by the I(h) inhibitor ZD7288 and appeared to be due to 5-HT modulation of I(h) as 5-HT shifted the activation curve of I(h) in a depolarizing fashion. Serotonin is thus likely to influence, in a composite fashion, the information processing of Layer II neurons in the mEC and thus, the passage of neocortical information via the perforant pathway to the hippocampus.
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Affiliation(s)
- Li Ma
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Smetana RW, Alford S, Dubuc R. Muscarinic receptor activation elicits sustained, recurring depolarizations in reticulospinal neurons. J Neurophysiol 2007; 97:3181-92. [PMID: 17344371 PMCID: PMC2397553 DOI: 10.1152/jn.00954.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In lampreys, brain stem reticulospinal (RS) neurons constitute the main descending input to the spinal cord and activate the spinal locomotor central pattern generators. Cholinergic nicotinic inputs activate RS neurons, and consequently, induce locomotion. Cholinergic muscarinic agonists also induce locomotion when applied to the brain stem of birds. This study examined whether bath applications of muscarinic agonists could activate RS neurons and initiate motor output in lampreys. Bath applications of 25 microM muscarine elicited sustained, recurring depolarizations (mean duration of 5.0 +/- 0.5 s recurring with a mean period of 55.5 +/- 10.3 s) in intracellularly recorded rhombencephalic RS neurons. Calcium imaging experiments revealed that muscarine induced oscillations in calcium levels that occurred synchronously within the RS neuron population. Bath application of TTX abolished the muscarine effect, suggesting the sustained depolarizations in RS neurons are driven by other neurons. A series of lesion experiments suggested the caudal half of the rhombencephalon was necessary. Microinjections of muscarine (75 microM) or the muscarinic receptor (mAchR) antagonist atropine (1 mM) lateral to the rostral pole of the posterior rhombencephalic reticular nucleus induced or prevented, respectively, the muscarinic RS neuron response. Cells immunoreactive for muscarinic receptors were found in this region and could mediate this response. Bath application of glutamatergic antagonists (6-cyano-7-nitroquinoxaline-2,3-dione/D-2-amino-5-phosphonovaleric acid) abolished the muscarine effect, suggesting that glutamatergic transmission is needed for the effect. Ventral root recordings showed spinal motor output coincides with RS neuron sustained depolarizations. We propose that unilateral mAchR activation on specific cells in the caudal rhombencephalon activates a circuit that generates synchronous sustained, recurring depolarizations in bilateral populations of RS neurons.
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Affiliation(s)
- R. W. Smetana
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - S. Alford
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - R. Dubuc
- Département de Kinanthropologie, Université du Québec à Montréal, Montreal, Quebec
- Centre de Recherche en Sciences Neurologiques, Université de Montréal, Montreal, Quebec, Canada
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Tsutsui H, Oka Y. Ion channels and their neural functions: contribution to general problems from studies of brains in non-mammalian species. BRAIN, BEHAVIOR AND EVOLUTION 2007; 69:122-31. [PMID: 17230020 DOI: 10.1159/000095201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ion channels and their neural functions have often been studied in the brains of mammals. However, the brains of some teleost fish species have special features that, at first glance, appear to be atypical and peculiar to that species alone. These teleost fish will contribute considerably to the understanding of general features of the ion channels and their neural functions. We have been interested in the neural mechanisms underlying the adaptive and flexible response of animals to changing environments and have been studying gonadotropin-releasing hormone (GnRH) peptidergic neuron systems, which we think are central for controlling such biologically adaptive responses. We have also been interested in a pretectal nucleus, corpus glomerulosum, which is tentatively regarded to play important roles in the organization of visually-guided feeding behaviors. In both systems, we found that certain types of apparently 'non-typical' Na(+) channels play important roles in neurobiological functions. Here we discuss how the study of functions of these apparently non-typical ion channels might contribute to our understanding of neural functions of vertebrate brains in general.
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Affiliation(s)
- Hidekazu Tsutsui
- Laboratory for Cell Function Dynamics, Brain Science Institute, RIKEN, Saitama, Japan
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42
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Pervouchine DD, Netoff TI, Rotstein HG, White JA, Cunningham MO, Whittington MA, Kopell NJ. Low-dimensional maps encoding dynamics in entorhinal cortex and hippocampus. Neural Comput 2006; 18:2617-50. [PMID: 16999573 DOI: 10.1162/neco.2006.18.11.2617] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Cells that produce intrinsic theta oscillations often contain the hyperpolarization-activated current I(h). In this article, we use models and dynamic clamp experiments to investigate the synchronization properties of two such cells (stellate cells of the entorhinal cortex and O-LM cells of the hippocampus) in networks with fast-spiking (FS) interneurons. The model we use for stellate cells and O-LM cells is the same, but the stellate cells are excitatory and the O-LM cells are inhibitory, with inhibitory postsynaptic potential considerably longer than those from FS interneurons. We use spike time response curve methods (STRC), expanding that technique to three-cell networks and giving two different ways in which the analysis of the three-cell network reduces to that of a two-cell network. We show that adding FS cells to a network of stellate cells can desynchronize the stellate cells, while adding them to a network of O-LM cells can synchronize the O-LM cells. These synchronization and desynchronization properties critically depend on I(h). The analysis of the deterministic system allows us to understand some effects of noise on the phase relationships in the stellate networks. The dynamic clamp experiments use biophysical stellate cells and in silico FS cells, with connections that mimic excitation or inhibition, the latter with decay times associated with FS cells or O-LM cells. The results obtained in the dynamic clamp experiments are in a good agreement with the analytical framework.
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Affiliation(s)
- Dmitri D Pervouchine
- Department of Mathematics and Statistics and Center for BioDynamics, Boston University, Boston, MA 02215, USA.
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Theta phase coding in a network model of the entorhinal cortex layer II with entorhinal-hippocampal loop connections. Cogn Neurodyn 2006; 1:169-84. [PMID: 19003510 DOI: 10.1007/s11571-006-9003-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Accepted: 08/08/2006] [Indexed: 10/24/2022] Open
Abstract
We investigated successive firing of the stellate cells within a theta cycle, which replicates the phase coding of place information, using a network model of the entorhinal cortex layer II with loop connections. Layer II of the entorhinal cortex (ECII) sends signals to the hippocampus, and the hippocampus sends signals back to layer V of the entorhinal cortex (ECV). In addition to this major pathway, projection from ECV to ECII also exists. It is, therefore, inferred that reverberation activity readily appears if projections from ECV to ECII are potentiated. The frequency of the reverberation would be in a gamma range because it takes signals 20-30 ms to go around the entorhinal-hippocampal loop circuits. On the other hand, it has been suggested that ECII is a theta rhythm generator. If the reverberation activity appears in the entorhinal-hippocampal loop circuits, gamma oscillation would be superimposed on a theta rhythm in ECII like a gamma-theta oscillation. This is a reminiscence of the theta phase coding of place information. In this paper, first, a network model of ECII will be developed in order to reproduce a theta rhythm. Secondly, we will show that loop connections from one stellate cell to the other one are selectively potentiated by afferent signals to ECII. Frequencies of those afferent signals are different, and transmission delay of the loop connections is 20 ms. As a result, stellate cells fire successively within one cycle of the theta rhythm. This resembles gamma-theta oscillation underlying the phase coding. Our model also replicates the phase precession of stellate cell firing within a cycle of subthreshold oscillation (theta rhythm).
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Rotstein HG, Oppermann T, White JA, Kopell N. The dynamic structure underlying subthreshold oscillatory activity and the onset of spikes in a model of medial entorhinal cortex stellate cells. J Comput Neurosci 2006; 21:271-92. [PMID: 16927211 DOI: 10.1007/s10827-006-8096-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Revised: 02/26/2006] [Accepted: 03/01/2006] [Indexed: 10/24/2022]
Abstract
Medial entorhinal cortex layer II stellate cells display subthreshold oscillations (STOs). We study a single compartment biophysical model of such cells which qualitatively reproduces these STOs. We argue that in the subthreshold interval (STI) the seven-dimensional model can be reduced to a three-dimensional system of equations with well differentiated times scales. Using dynamical systems arguments we provide a mechanism for generations of STOs. This mechanism is based on the "canard structure," in which relevant trajectories stay close to repelling manifolds for a significant interval of time. We also show that the transition from subthreshold oscillatory activity to spiking ("canard explosion") is controlled in the STI by the same structure. A similar mechanism is invoked to explain why noise increases the robustness of the STO regime. Taking advantage of the reduction of the dimensionality of the full stellate cell system, we propose a nonlinear artificially spiking (NAS) model in which the STI reduced system is supplemented with a threshold for spiking and a reset voltage. We show that the synchronization properties in networks made up of the NAS cells are similar to those of networks using the full stellate cell models.
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Affiliation(s)
- Horacio G Rotstein
- Department of Mathematics and Center for Biodynamics, Boston University, Boston, MA 02215, USA
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Rosenkranz JA, Johnston D. Dopaminergic regulation of neuronal excitability through modulation of Ih in layer V entorhinal cortex. J Neurosci 2006; 26:3229-44. [PMID: 16554474 PMCID: PMC6674109 DOI: 10.1523/jneurosci.4333-05.2006] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The entorhinal cortex (EC) is a significant component of the systems that underlie certain forms of memory formation and recall. Evidence has been emerging that the dopaminergic system in the EC facilitates these and other functions of the EC. The effects of dopamine (DA) on membrane properties and excitability of EC neurons, however, are not known. We used in vitro whole-cell patch-clamp recordings from layer V pyramidal neuronal somata and dendrites of the adult rat lateral EC to investigate the effects of DA on the excitability of these neurons. We found that brief application of DA caused a reduction in the excitability of layer V EC pyramidal neurons. This effect was attributable to voltage-dependent modification of membrane properties that can best be explained by an increase in a hyperpolarization-activated conductance. Furthermore, the effects of DA were blocked by pharmacological blockade of h-channels, but not by any of a number of other ion channels. These actions were produced by a D1 receptor-mediated increase of cAMP but were independent of protein kinase A. A portion of the actions of DA can be attributed to effects in the apical dendrites. The data suggest that DA can directly influence the membrane properties of layer V EC pyramidal neurons by modulation of h-channels. These actions may underlie some of the effects of DA on memory formation.
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Affiliation(s)
- J Amiel Rosenkranz
- Center for Learning and Memory, University of Texas, Austin, Texas 78712, USA.
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Sanhueza M, Bacigalupo J. Intrinsic subthreshold oscillations of the membrane potential in pyramidal neurons of the olfactory amygdala. Eur J Neurosci 2006; 22:1618-26. [PMID: 16197502 DOI: 10.1111/j.1460-9568.2005.04341.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The amygdala complex is a heterogeneous group of temporal lobe brain structures involved in the processing of biologically significant sensory stimuli and in the generation of appropriate responses to them. The amygdala has also been implicated in certain forms of emotional learning and memory. While much progress has been made in understanding neural processing in the basolateral subgroup of the amygdala, physiological studies in the cortical regions of the complex, also known as olfactory amygdala, are missing. Using a rat brain slice preparation, we conducted whole-cell recordings on pyramidal neurons of the periamygdaloid cortex and the anterior cortical nucleus, two structures receiving direct connections from the olfactory bulb. Upon depolarization by current injection through the recording electrode, a fraction of periamygdaloid cortex and most anterior cortical nucleus layer II pyramidal neurons displayed an intermittent discharge pattern, where clusters of action potentials were interspersed by periods of membrane potential subthreshold oscillations. Oscillations frequency increased with membrane potential and correlated linearly with the cluster spiking frequency. Frequency ranged from 3 to 20 Hz, considering different cells and membrane potential values (up to approximately 30 mV above resting potentials of typically approximately -70 mV). Subthreshold oscillations were preserved after pharmacological inhibition of fast excitatory and inhibitory synaptic transmission, but were abolished by application of the sodium channel blocker tetrodotoxin. We conclude that pyramidal neurons of the olfactory cortical amygdala display intrinsically generated voltage-dependent membrane potential rhythmic fluctuations in the theta-low beta range, requiring the activation of a sodium conductance.
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Affiliation(s)
- Magdalena Sanhueza
- Department of Biology, Faculty of Sciences and Cell Dynamics and Biotechnology Research Center, University of Chile, Casilla 653 Santiago, Chile.
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Chrobak JJ, Sabolek HR, Bunce JG. Intraseptal cholinergic infusions alter memory in the rat: method and mechanism. EXS 2006; 98:87-98. [PMID: 17019884 DOI: 10.1007/978-3-7643-7772-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- James J Chrobak
- Department of Psychology, University of Connecticut, Storrs, CT 06269, USA.
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Chen X, Shu S, Bayliss DA. Suppression of ih contributes to propofol-induced inhibition of mouse cortical pyramidal neurons. J Neurophysiol 2005; 94:3872-83. [PMID: 16093340 DOI: 10.1152/jn.00389.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The contributions of the hyperpolarization-activated current, I(h), to generation of rhythmic activities are well described for various central neurons, particularly in thalamocortical circuits. In the present study, we investigated effects of a general anesthetic, propofol, on native I(h) in neurons of thalamus and cortex and on the corresponding cloned HCN channel subunits. Whole cell voltage-clamp recordings from mouse brain slices identified neuronal I(h) currents with fast activation kinetics in neocortical pyramidal neurons and with slower kinetics in thalamocortical relay cells. Propofol inhibited the fast-activating I(h) in cortical neurons at a clinically relevant concentration (5 microM); inhibition of I(h) involved a hyperpolarizing shift in half-activation voltage (DeltaV1/2 approximately -9 mV) and a decrease in maximal available current (approximately 36% inhibition, measured at -120 mV). With the slower form of I(h) expressed in thalamocortical neurons, propofol had no effect on current activation or amplitude. In heterologous expression systems, 5 muM propofol caused a large shift in V1/2 and decrease in current amplitude in homomeric HCN1 and linked heteromeric HCN1-HCN2 channels, both of which activate with fast kinetics but did not affect V1/2 or current amplitude of slowly activating homomeric HCN2 channels. With GABA(A) and glycine receptor channels blocked, propofol caused membrane hyperpolarization and suppressed action potential discharge in cortical neurons; these effects were occluded by the I(h) blocker, ZD-7288. In summary, these data indicate that propofol selectively inhibits HCN channels containing HCN1 subunits, such as those that mediate I(h) in cortical pyramidal neurons-and they suggest that anesthetic actions of propofol may involve inhibition of cortical neurons and perhaps other HCN1-expressing cells.
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Affiliation(s)
- Xiangdong Chen
- Department of Pharmacology, University of Virginia, Charlottesville, 22908-0735, USA.
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Tolner EA, Kloosterman F, Kalitzin SN, da Silva FHL, Gorter JA. Physiological changes in chronic epileptic rats are prominent in superficial layers of the medial entorhinal area. Epilepsia 2005; 46 Suppl 5:72-81. [PMID: 15987257 DOI: 10.1111/j.1528-1167.2005.01012.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE We investigated whether the functional network properties of the medial entorhinal area (MEA) of the entorhinal cortex were altered in a rat model of chronic epilepsy that is characterized by extensive cell loss in MEA layer III. METHODS Responses were evoked in the entorhinal cortex by electrical stimulation of the subiculum in anesthetized chronic epileptic rats, 2-4 months after status epilepticus, induced by systemic kainate (KA) injections. Laminar field potentials were measured using a 16-channel silicon probe that covered all six layers of the MEA; an estimate of the local transmembrane currents was made using current source density analysis. RESULTS Double-pulse stimulation of the subiculum evoked responses in deep and superficial layers of the MEA in control and KA rats. A current sink in layer I and at the border of layer I and II that was induced by antidromic activation of MEA-II, was much more prominent in KA rats with extensive neuronal loss in MEA-III than in control rats or KA rats with minor MEA-III loss. Furthermore, KA rats that displayed MEA-III loss presented a series of oscillations induced by subicular stimulation in the beta/gamma-frequency range (20-100 Hz), which were confined to superficial layers of MEA. These oscillations were never observed in control rats or KA rats with minor MEA-III loss. CONCLUSIONS These results indicate that the observed alterations in the superficial MEA responses to subiculum stimulation and the occurrence of beta/gamma-oscillations are related phenomena, which are a consequence of altered and impaired inhibition within these MEA layers in chronic epileptic rats.
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Affiliation(s)
- Else A Tolner
- Swammerdam Institute of Life Sciences, Center for Neuroscience, University of Amsterdam, Graduate School of Neurosciences Amsterdam, Amsterdam, The Netherlands
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Caruana DA, Chapman CA. Stimulation of the Parasubiculum Modulates Entorhinal Cortex Responses to Piriform Cortex Inputs In Vivo. J Neurophysiol 2004; 92:1226-35. [PMID: 15044514 DOI: 10.1152/jn.00038.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Although a major output of the hippocampal formation is from the subiculum to the deep layers of the entorhinal cortex, the parasubiculum projects to the superficial layers of the entorhinal cortex and may therefore modulate how the entorhinal cortex responds to sensory inputs from other cortical regions. Recordings at multiple depths in the entorhinal cortex were first used to characterize field potentials evoked by stimulation of the parasubiculum in urethan-anesthetized rats. Current source density analysis showed that a prominent surface-negative field potential component is generated by synaptic activation in layer II. The surface-negative field potential was also observed in rats with chronically implanted electrodes. The response was maintained during short stimulation trains of ≤125 Hz, suggesting that it is generated by activation of monosynaptic inputs to the entorhinal cortex. The piriform cortex also projects to layer II of the entorhinal cortex, and interactions between parasubicular and piriform cortex inputs were investigated using double-site stimulation tests. Simultaneous activation of parasubicular and piriform cortex inputs with high-intensity pulses resulted in smaller synaptic potentials than were expected on the basis of summing the individual responses, consistent with the termination of both pathways onto a common population of neurons. Paired-pulse tests were then used to assess the effect of parasubicular stimulation on responses to piriform cortex stimulation. Responses of the entorhinal cortex to piriform cortex inputs were inhibited when the parasubiculum was stimulated 5 ms earlier and were enhanced when the parasubiculum was stimulated 20–150 ms earlier. These results indicate that excitatory inputs to the entorhinal cortex from the parasubiculum may enhance the propagation of neuronal activation patterns into the hippocampal circuit by increasing the responsiveness of the entorhinal cortex to appropriately timed inputs.
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Affiliation(s)
- Douglas A Caruana
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, 7141 Sherbrooke St. W., Room SP-244, Montréal, Québec H4B 1R6, Canada.
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