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Borjas NC, Anstötz M, Maccaferri G. Multiple layers of diversity govern the cell type specificity of GABAergic input received by mouse subicular pyramidal neurons. J Physiol 2024; 602:4195-4213. [PMID: 39141819 DOI: 10.1113/jp286679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 07/23/2024] [Indexed: 08/16/2024] Open
Abstract
The subiculum is a key region of the brain involved in the initiation of pathological activity in temporal lobe epilepsy, and local GABAergic inhibition is essential to prevent subicular-originated epileptiform discharges. Subicular pyramidal cells may be easily distinguished into two classes based on their different firing patterns. Here, we have compared the strength of the GABAa receptor-mediated inhibitory postsynaptic currents received by regular- vs. burst-firing subicular neurons and their dynamic modulation by the activation of μ opioid receptors. We have taken advantage of the sequential re-patching of the same cell to initially classify pyramidal neurons according to their firing patters, and then to measure GABAergic events triggered by the optogenetic stimulation of parvalbumin- and somatostatin-expressing interneurons. Activation of parvalbumin-expressing cells generated larger responses in postsynaptic burst-firing neurons whereas the opposite was observed for currents evoked by the stimulation of somatostatin-expressing interneurons. In all cases, events depended critically on ω-agatoxin IVA- but not on ω-conotoxin GVIA-sensitive calcium channels. Optogenetic GABAergic input originating from both parvalbumin- and somatostatin-expressing cells was reduced in amplitude following the exposure to a μ opioid receptor agonist. The kinetics of this pharmacological sensitivity was different in regular- vs. burst-firing neurons, but only when responses were evoked by the activation of parvalbumin-expressing neurons, whereas no differences were observed when somatostatin-expressing cells were stimulated. In conclusion, our results show that a high degree of complexity regulates the organizing principles of subicular GABAergic inhibition, with the interaction of pre- and postsynaptic diversity at multiple levels. KEY POINTS: Optogenetic stimulation of parvalbumin- and somatostatin-expressing interneurons (PVs and SOMs) triggers inhibitory postsynaptic currents (IPSCs) in both regular- and burst-firing (RFs and BFs) subicular pyramidal cells. The amplitude of optogenetically evoked IPSCs from PVs (PV-opto IPSCs) is larger in BFs whereas IPSCs generated by the light activation of SOMs (SOM-opto IPSCs) are larger in RFs. Both PV- and SOM-opto IPSCs critically depend on ω-agatoxin IVA-sensitive P/Q type voltage-gated calcium channels, whereas no major effects are observed following exposure to ω-conotoxin GVIA, suggesting no significant involvement of N-type channels. The amplitude of both PV- and SOM-opto IPSCs is reduced by the probable pharmacological activation of presynaptic μ opioid receptors, with a faster kinetics of the effect observed in PV-opto IPSCs from RFs vs. BFs, but not in SOM-opto IPSCs. These results help us understand the complex interactions between different layers of diversity regulating GABAergic input onto subicular microcircuits.
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Affiliation(s)
- Nancy Castro Borjas
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, USA
| | - Max Anstötz
- Institute of Anatomy II, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Gianmaria Maccaferri
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, USA
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Franz J, Barheier N, Wilms H, Tulke S, Haas CA, Häussler U. Differential vulnerability of neuronal subpopulations of the subiculum in a mouse model for mesial temporal lobe epilepsy. Front Cell Neurosci 2023; 17:1142507. [PMID: 37066079 PMCID: PMC10090355 DOI: 10.3389/fncel.2023.1142507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/06/2023] [Indexed: 03/30/2023] Open
Abstract
Selective loss of inhibitory interneurons (INs) that promotes a shift toward an excitatory predominance may have a critical impact on the generation of epileptic activity. While research on mesial temporal lobe epilepsy (MTLE) has mostly focused on hippocampal changes, including IN loss, the subiculum as the major output region of the hippocampal formation has received less attention. The subiculum has been shown to occupy a key position in the epileptic network, but data on cellular alterations are controversial. Using the intrahippocampal kainate (KA) mouse model for MTLE, which recapitulates main features of human MTLE such as unilateral hippocampal sclerosis and granule cell dispersion, we identified cell loss in the subiculum and quantified changes in specific IN subpopulations along its dorso-ventral axis. We performed intrahippocampal recordings, FluoroJade C-staining for degenerating neurons shortly after status epilepticus (SE), fluorescence in situ hybridization for glutamic acid decarboxylase (Gad) 67 mRNA and immunohistochemistry for neuronal nuclei (NeuN), parvalbumin (PV), calretinin (CR) and neuropeptide Y (NPY) at 21 days after KA. We observed remarkable cell loss in the ipsilateral subiculum shortly after SE, reflected in lowered density of NeuN+ cells in the chronic stage when epileptic activity occurred in the subiculum concomitantly with the hippocampus. In addition, we show a position-dependent reduction of Gad67-expressing INs by ∼50% (along the dorso-ventral as well as transverse axis of the subiculum). This particularly affected the PV- and to a lesser extent CR-expressing INs. The density of NPY-positive neurons was increased, but the double-labeling for Gad67 mRNA expression revealed that an upregulation or de novo expression of NPY in non-GABAergic cells with a concomitant reduction of NPY-positive INs underlies this observation. Our data suggest a position- and cell type-specific vulnerability of subicular INs in MTLE, which might contribute to hyperexcitability of the subiculum, reflected in epileptic activity.
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Affiliation(s)
- Julia Franz
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Nicole Barheier
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Henrike Wilms
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Susanne Tulke
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Carola A. Haas
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
| | - Ute Häussler
- Experimental Epilepsy Research, Department of Neurosurgery, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
- *Correspondence: Ute Häussler,
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Anstötz M, Fiske MP, Maccaferri G. Impaired KCC2 Function Triggers Interictal-Like Activity Driven by Parvalbumin-Expressing Interneurons in the Isolated Subiculum In Vitro. Cereb Cortex 2021; 31:4681-4698. [PMID: 33987649 PMCID: PMC8408463 DOI: 10.1093/cercor/bhab115] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 04/07/2021] [Accepted: 04/10/2021] [Indexed: 12/30/2022] Open
Abstract
The decreased expression of the KCC2 membrane transporter in subicular neurons has been proposed to be a key epileptogenic event in temporal lobe epilepsy (TLE). Here, we have addressed this question in a reduced model in vitro and have studied the properties and mechanistic involvement of a major class of interneurons, that is, parvalbumin-expressing cells (PVs). When exposed to the KCC2 blocker VU0463271, mouse subicular slices generated hypersynchronous discharges that could be recorded electrophysiologically and visualized as clusters of co-active neurons with calcium imaging. The pharmacological profile of these events resembled interictal-like discharges in human epileptic tissue because of their dependence on GABAA and AMPA receptors. On average, PVs fired before pyramidal cells (PCs) and the area of co-active clusters was comparable to the individual axonal spread of PVs, suggesting their mechanistic involvement. Optogenetic experiments confirmed this hypothesis, as the flash-stimulation of PVs in the presence of VU0463271 initiated interictal-like discharges, whereas their optogenetic silencing suppressed network hyper-excitability. We conclude that reduced KCC2 activity in subicular networks in vitro is sufficient to induce interictal-like activity via altered GABAergic signaling from PVs without other epilepsy-related changes. This conclusion supports an epileptogenic role for impaired subicular KCC2 function during the progression of TLE.
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Affiliation(s)
- Max Anstötz
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Michael Patrick Fiske
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Gianmaria Maccaferri
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Ng XW, Chung YH, Piston DW. Intercellular Communication in the Islet of Langerhans in Health and Disease. Compr Physiol 2021; 11:2191-2225. [PMID: 34190340 PMCID: PMC8985231 DOI: 10.1002/cphy.c200026] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.
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Affiliation(s)
- Xue W Ng
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - Yong H Chung
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
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Fei F, Wang X, Wang Y, Chen Z. Dissecting the role of subiculum in epilepsy: Research update and translational potential. Prog Neurobiol 2021; 201:102029. [PMID: 33636224 DOI: 10.1016/j.pneurobio.2021.102029] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 01/12/2021] [Accepted: 02/21/2021] [Indexed: 11/25/2022]
Abstract
The subiculum serves as the strategic core output of the hippocampus, through which neural activity exits the hippocampal proper and targets the entorhinal cortex and other more distant subcortical and cortical areas. The past decade has witnessed a growing interest in the subiculum, owing to discoveries revealing its critical role in regulating many physiological and pathophysiological processes. Notably, accumulating evidence from both clinical and experimental studies suggests that the subiculum plays a vital role in seizure initiation and propagation, in epilepsy. In this review, we briefly describe the structure and connectivity of the subiculum and then summarize the molecular and cellular mechanisms in the subiculum underlying the epileptic brain, in both epilepsy patients and animal models. Next, we review some translational approaches targeting the malfunctioned subiculum to treat epilepsy. Finally, we pose open questions for future research in the subiculum and their clinical translation challenges.
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Affiliation(s)
- Fan Fei
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Xia Wang
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Key Laboratory of Neuropharmacology and Translational Medicine of Zhejiang Province, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Key Laboratory of Neuropharmacology and Translational Medicine of Zhejiang Province, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China; Epilepsy Center, Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
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Lévesque M, Avoli M. The subiculum and its role in focal epileptic disorders. Rev Neurosci 2020; 32:249-273. [PMID: 33661586 DOI: 10.1515/revneuro-2020-0091] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/29/2020] [Indexed: 01/07/2023]
Abstract
The subicular complex (hereafter referred as subiculum), which is reciprocally connected with the hippocampus and rhinal cortices, exerts a major control on hippocampal outputs. Over the last three decades, several studies have revealed that the subiculum plays a pivotal role in learning and memory but also in pathological conditions such as mesial temporal lobe epilepsy (MTLE). Indeed, subicular networks actively contribute to seizure generation and this structure is relatively spared from the cell loss encountered in this focal epileptic disorder. In this review, we will address: (i) the functional properties of subicular principal cells under normal and pathological conditions; (ii) the subiculum role in sustaining seizures in in vivo models of MTLE and in in vitro models of epileptiform synchronization; (iii) its presumptive role in human MTLE; and (iv) evidence underscoring the relationship between subiculum and antiepileptic drug effects. The studies reviewed here reinforce the view that the subiculum represents a limbic area with relevant, as yet unexplored, roles in focal epilepsy.
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Affiliation(s)
- Maxime Lévesque
- Departments of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
| | - Massimo Avoli
- Departments of Neurology, Neurosurgery, and Physiology, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
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Witter MP, Amaral DG. The entorhinal cortex of the monkey: VI. Organization of projections from the hippocampus, subiculum, presubiculum, and parasubiculum. J Comp Neurol 2020; 529:828-852. [DOI: 10.1002/cne.24983] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/29/2020] [Accepted: 06/30/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Menno P. Witter
- Department of Psychiatry and Behavioral Sciences The MIND Institute and the California National Primate Research Center Davis California USA
| | - David G. Amaral
- Department of Psychiatry and Behavioral Sciences The MIND Institute and the California National Primate Research Center Davis California USA
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