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Arias ER, Sánchez-Tafolla BM, Terrón C, Martínez LA, Zetina ME, Morales MA, Cifuentes F. Long-term potentiation and its neurotrophin-dependent modulation in the superior cervical ganglion of the rat are influenced by KCNQ channel function. Can J Physiol Pharmacol 2023; 101:539-547. [PMID: 37406358 DOI: 10.1139/cjpp-2022-0552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023]
Abstract
Ganglionic long-term potentiation (gLTP) in the rat superior cervical ganglion (SCG) is differentially modulated by neurotrophic factors (Nts): brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). KCNQ/M channels, key regulators of neuronal excitability, and firing pattern are modulated by Nts; therefore, they might contribute to gLTP expression and to the Nts-dependent modulation of gLTP. In the SCG of rats, we characterized the presence of the KCNQ2 isoform and the effects of opposite KCNQ/M channel modulators on gLTP in control condition and under Nts modulation. Immunohistochemical and reverse transcriptase polymerase chain reaction analyses showed the expression of the KCNQ2 isoform. We found that 1 µmol/L XE991, a channel inhibitor, significantly reduced gLTP (∼50%), whereas 5 µmol/L flupirtine, a channel activator, significantly increased gLTP (1.3- to 1.7-fold). Both modulators counterbalanced the effects of the Nts on gLTP. Data suggest that KCNQ/M channels are likely involved in gLTP expression and in the modulation exerted by BDNF and NGF.
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Affiliation(s)
- Erwin R Arias
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Berardo M Sánchez-Tafolla
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Carlos Terrón
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Luis A Martínez
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Maria E Zetina
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Miguel A Morales
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
| | - Fredy Cifuentes
- Departamento de Biología Celular & Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, C.U., Coyoacán 04510, Ciudad de México, México
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Estades Ayuso V, Pickles S, Todd T, Yue M, Jansen-West K, Song Y, González Bejarano J, Rawlinson B, DeTure M, Graff-Radford NR, Boeve BF, Knopman DS, Petersen RC, Dickson DW, Josephs KA, Petrucelli L, Prudencio M. TDP-43-regulated cryptic RNAs accumulate in Alzheimer's disease brains. Mol Neurodegener 2023; 18:57. [PMID: 37605276 PMCID: PMC10441763 DOI: 10.1186/s13024-023-00646-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/04/2023] [Indexed: 08/23/2023] Open
Abstract
BACKGROUND Inclusions of TAR DNA-binding protein 43 kDa (TDP-43) has been designated limbic-predominant, age-related TDP-43 encephalopathy (LATE), with or without co-occurrence of Alzheimer's disease (AD). Approximately, 30-70% AD cases present TDP-43 proteinopathy (AD-TDP), and a greater disease severity compared to AD patients without TDP-43 pathology. However, it remains unclear to what extent TDP-43 dysfunction is involved in AD pathogenesis. METHODS To investigate whether TDP-43 dysfunction is a prominent feature in AD-TDP cases, we evaluated whether non-conserved cryptic exons, which serve as a marker of TDP-43 dysfunction in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), accumulate in AD-TDP brains. We assessed a cohort of 192 post-mortem brains from three different brain regions: amygdala, hippocampus, and frontal cortex. Following RNA and protein extraction, qRT-PCR and immunoassays were performed to quantify the accumulation of cryptic RNA targets and phosphorylated TDP-43 pathology, respectively. RESULTS We detected the accumulation of misspliced cryptic or skiptic RNAs of STMN2, KCNQ2, UNC13A, CAMK2B, and SYT7 in the amygdala and hippocampus of AD-TDP cases. The topographic distribution of cryptic RNA accumulation mimicked that of phosphorylated TDP-43, regardless of TDP-43 subtype classification. Further, cryptic RNAs efficiently discriminated AD-TDP cases from controls. CONCLUSIONS Overall, our results indicate that cryptic RNAs may represent an intriguing new therapeutic and diagnostic target in AD, and that methods aimed at detecting and measuring these species in patient biofluids could be used as a reliable tool to assess TDP-43 pathology in AD. Our work also raises the possibility that TDP-43 dysfunction and related changes in cryptic splicing could represent a common molecular mechanism shared between AD-TDP and FTLD-TDP.
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Affiliation(s)
- Virginia Estades Ayuso
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | - Sarah Pickles
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | - Tiffany Todd
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | - Mei Yue
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | | | - Yuping Song
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | | | | | - Michael DeTure
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | | | | | | | | | - Dennis W Dickson
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | | | - Leonard Petrucelli
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA
| | - Mercedes Prudencio
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.
- Neuroscience Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL, USA.
- Department of Research, Neuroscience, Mayo Clinic College of Medicine, 4500 San Pablo Rd, Jacksonville, FL, 32224, USA.
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3
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Tracy GC, Wilton AR, Rhodes JS, Chung HJ. Heterozygous Deletion of Epilepsy Gene KCNQ2 Has Negligible Effects on Learning and Memory. Front Behav Neurosci 2022; 16:930216. [PMID: 35928789 PMCID: PMC9344800 DOI: 10.3389/fnbeh.2022.930216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 06/10/2022] [Indexed: 11/13/2022] Open
Abstract
Neuronal Kv7/Potassium Voltage-Gated Channel Subfamily Q (KCNQ) potassium channels underlie M-current that potently suppresses repetitive and burst firing of action potentials (APs). They are mostly heterotetramers of Kv7.2 and Kv7.3 subunits in the hippocampus and cortex, the brain regions important for cognition and behavior. Underscoring their critical roles in inhibiting neuronal excitability, autosomal dominantly inherited mutations in Potassium Voltage-Gated Channel Subfamily Q Member 2 (KCNQ2) and Potassium Voltage-Gated Channel Subfamily Q Member 3 (KCNQ3) genes are associated with benign familial neonatal epilepsy (BFNE) in which most seizures spontaneously remit within months without cognitive deficits. De novo mutations in KCNQ2 also cause epileptic encephalopathy (EE), which is characterized by persistent seizures that are often drug refractory, neurodevelopmental delay, and intellectual disability. Heterozygous expression of EE variants of KCNQ2 is recently shown to induce spontaneous seizures and cognitive deficit in mice, although it is unclear whether this cognitive deficit is caused directly by Kv7 disruption or by persistent seizures in the developing brain as a consequence of Kv7 disruption. In this study, we examined the role of Kv7 channels in learning and memory by behavioral phenotyping of the KCNQ2+/− mice, which lack a single copy of KCNQ2 but dos not display spontaneous seizures. We found that both KCNQ2+/− and wild-type (WT) mice showed comparable nociception in the tail-flick assay and fear-induced learning and memory during a passive inhibitory avoidance (IA) test and contextual fear conditioning (CFC). Both genotypes displayed similar object location and recognition memory. These findings together provide evidence that heterozygous loss of KCNQ2 has minimal effects on learning or memory in mice in the absence of spontaneous seizures.
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Affiliation(s)
- Gregory C. Tracy
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Angelina R. Wilton
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Justin S. Rhodes
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Psychology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Hee Jung Chung
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- *Correspondence: Hee Jung Chung
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Ye H, Liu ZX, He YJ, Wang X. Effects of M currents on the persistent activity of pyramidal neurons in mouse primary auditory cortex. J Neurophysiol 2022; 127:1269-1278. [PMID: 35294269 DOI: 10.1152/jn.00332.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuronal persistent activity (PA) is a common phenomenon observed in many types of neurons. PA can be induced in neurons in the mouse auditory nucleus by activating cholinergic receptors with carbachol (CCh), a dual muscarinic and nicotinic receptor agonist. PA is presumed to be associated with learning-related auditory plasticity at the cellular level. However, the mechanism is not clearly understood. Many studies have reported that muscarinic cholinergic receptor agonists inhibit muscarinic-sensitive potassium channels (M channels). Potassium influx through M channels produces potassium currents, called M currents, which play an essential role in regulating neural excitability and synaptic plasticity. Further study is needed to determine whether M currents affect the PA of auditory central neurons and provide additional analysis of the variations in electrophysiological properties. We used in vitro whole-cell patch-clamp recordings in isolated mouse brain slices to investigate the effects of M currents on the PA in pyramidal neurons in layer V of the primary auditory cortex (AI-L5). We found that blocking M currents with XE991 depolarized the AI-L5 pyramidal neurons, which significantly increased the input resistance. The active threshold and threshold intensity were significantly reduced, indicating that the intrinsic excitability was enhanced. Our results also showed that blocking M currents with XE991 switched the neuronal firing patterns in the AI-L5 pyramidal neurons from regular-spiking to intrinsic-bursting. Blocking M currents facilitated PA by increasing the plateau potential and enhancing intrinsic excitability. Our results suggested that blocking M currents might facilitate the PA in AI-L5 pyramidal neurons, which underlies auditory plasticity.
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Affiliation(s)
- Huan Ye
- Hubei Key Lab of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Zhen-Xu Liu
- Hubei Key Lab of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Ya-Jie He
- Hubei Key Lab of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Xin Wang
- Hubei Key Lab of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
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5
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Zheng Y, Liu H, Chen Y, Dong S, Wang F, Wang S, Li GL, Shu Y, Xu F. Structural insights into the lipid and ligand regulation of a human neuronal KCNQ channel. Neuron 2021; 110:237-247.e4. [PMID: 34767770 DOI: 10.1016/j.neuron.2021.10.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 09/20/2021] [Accepted: 10/19/2021] [Indexed: 01/10/2023]
Abstract
The KCNQ family (KCNQ1-KCNQ5) of voltage-gated potassium channels plays critical roles in many physiological and pathological processes. It is known that the channel opening of all KCNQs relies on the signaling lipid molecule phosphatidylinositol 4,5-bisphosphate (PIP2). However, the molecular mechanism of PIP2 in modulating the opening of the four neuronal KCNQ channels (KCNQ2-KCNQ5), which are essential for regulating neuronal excitability, remains largely elusive. Here, we report the cryoelectron microscopy (cryo-EM) structures of human KCNQ4 determined in complex with the activator ML213 in the absence or presence of PIP2. Two PIP2 molecules are identified in the open-state structure of KCNQ4, which act as a bridge to couple the voltage-sensing domain (VSD) and pore domain (PD) of KCNQ4 leading to the channel opening. Our findings reveal the binding sites and activation mechanisms of ML213 and PIP2 for neuronal KCNQ channels, providing a framework for therapeutic intervention targeting on these important channels.
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Affiliation(s)
- You Zheng
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Heng Liu
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yuxin Chen
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Shaowei Dong
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Fang Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Shengyi Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Geng-Lin Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Yilai Shu
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China.
| | - Fei Xu
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China.
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6
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Baculis BC, Zhang J, Chung HJ. The Role of K v7 Channels in Neural Plasticity and Behavior. Front Physiol 2020; 11:568667. [PMID: 33071824 PMCID: PMC7530275 DOI: 10.3389/fphys.2020.568667] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/28/2020] [Indexed: 12/12/2022] Open
Abstract
Activity-dependent persistent changes in neuronal intrinsic excitability and synaptic strength are widely thought to underlie learning and memory. Voltage-gated KCNQ/Kv7 potassium channels have been of great interest as the potential targets for memory disorders due to the beneficial effects of their antagonists in cognition. Importantly, de novo dominant mutations in their neuronal subunits KCNQ2/Kv7.2 and KCNQ3/Kv7.3 are associated with epilepsy and neurodevelopmental disorder characterized by developmental delay and intellectual disability. The role of Kv7 channels in neuronal excitability and epilepsy has been extensively studied. However, their functional significance in neural plasticity, learning, and memory remains largely unknown. Here, we review recent studies that support the emerging roles of Kv7 channels in intrinsic and synaptic plasticity, and their contributions to cognition and behavior.
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Affiliation(s)
- Brian C Baculis
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Jiaren Zhang
- Department of Molecular Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Hee Jung Chung
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, United States.,Department of Molecular Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
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7
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Wang J, Yu W, Gao Q, Ju C, Wang K. Prefrontal inhibition of neuronal K v 7 channels enhances prepulse inhibition of acoustic startle reflex and resistance to hypofrontality. Br J Pharmacol 2020; 177:4720-4733. [PMID: 32839968 PMCID: PMC7520443 DOI: 10.1111/bph.15236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 07/31/2020] [Accepted: 08/06/2020] [Indexed: 11/28/2022] Open
Abstract
Background and Purpose Dysfunction of the prefrontal cortex (PFC) is involved in the cognitive deficits in neuropsychiatric diseases, such as schizophrenia, characterized by deficient neurotransmission known as NMDA receptor hypofrontality. Thus, enhancing prefrontal activity may alleviate hypofrontality‐induced cognitive deficits. To test this hypothesis, we investigated the effect of forebrain‐specific suppression or pharmacological inhibition of native Kv7/KCNQ/M‐current on glutamatergic hypofrontality induced by the NMDA receptor antagonist MK‐801. Experimental Approach The forebrain‐specific inhibition of native M‐current was generated by transgenic expression, in mice, of a dominant‐negative pore mutant G279S of Kv7.2/KCNQ2 channels that suppresses channel function. A mouse model of cognitive impairment was established by single i.p. injection of 0.1 mg·kg−1 MK‐801. Mouse models of prepulse inhibition (PPI) of acoustic startle reflex and Y‐maze spontaneous alternation test were used for evaluation of cognitive behaviour. Hippocampal brain slice recordings of LTP were used to assess synaptic plasticity. Hippocampus and cortex were dissected for detecting protein expression using western blot analysis. Key Results Genetic suppression of Kv7 channel function in the forebrain or pharmacological inhibition of Kv7 channels by the specific blocker XE991 enhanced PPI and also alleviated MK‐801 induced cognitive decline. XE991 also attenuated MK‐801‐induced LTP deficits and increased basal synaptic transmissions. Western blot analysis revealed that inhibiting Kv7 channels resulted in elevation of pAkt1 and pGSK‐3β expressions in both hippocampus and cortex. Conclusions and Implications Both genetic and pharmacological inhibition of Kv7 channels alleviated PPI and cognitive deficits. Mechanistically, inhibition of Kv7 channels promotes synaptic transmission and activates Akt1/GSK‐3β signalling.
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Affiliation(s)
- Jing Wang
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China
| | - Wenwen Yu
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China.,Institute of Innovative Drugs, Qingdao University, Qingdao, China
| | - Qin Gao
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China
| | - Chuanxia Ju
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China
| | - KeWei Wang
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China.,Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, China.,Institute of Innovative Drugs, Qingdao University, Qingdao, China
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8
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Fernández-Fernández D, Lamas JA. Metabotropic Modulation of Potassium Channels During Synaptic Plasticity. Neuroscience 2020; 456:4-16. [PMID: 32114098 DOI: 10.1016/j.neuroscience.2020.02.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 01/06/2023]
Abstract
Besides their primary function mediating the repolarization phase of action potentials, potassium channels exquisitely and ubiquitously regulate the resting membrane potential of neurons and therefore have a key role establishing their intrinsic excitability. This group of proteins is composed of a very diverse collection of voltage-dependent and -independent ion channels, whose specific distribution is finely tuned at the level of the synapse. Both at the presynaptic and postsynaptic membranes, different types of potassium channels are subjected to modulation by second messenger signaling cascades triggered by metabotropic receptors, which in this way serve as a link between neurotransmitter actions and changes in the neuron membrane excitability. On the one hand, by regulating the resting membrane potential of the postsynaptic membrane, potassium channels appear to be critical towards setting the threshold for the induction of long-term potentiation and depression. On the other hand, these channels maintain the presynaptic membrane potential under control, therefore influencing the probability of neurotransmitter release underlying different forms of short-term plasticity. In the present review, we examine in detail the role of metabotropic receptors translating their activation by different neurotransmitters into a final effect modulating several types of potassium channels. Furthermore, we evaluate the consequences that this interplay has on the induction and maintenance of different forms of synaptic plasticity.
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Affiliation(s)
- D Fernández-Fernández
- Laboratory of Neuroscience, Biomedical Research Center (CINBIO), University of Vigo, Vigo, Galicia, Spain.
| | - J A Lamas
- Laboratory of Neuroscience, Biomedical Research Center (CINBIO), University of Vigo, Vigo, Galicia, Spain
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9
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Armas-Capote N, Maglio LE, Pérez-Atencio L, Martin-Batista E, Reboreda A, Barios JA, Hernandez G, Alvarez de la Rosa D, Lamas JA, Barrio LC, Giraldez T. SGK1.1 Reduces Kainic Acid-Induced Seizure Severity and Leads to Rapid Termination of Seizures. Cereb Cortex 2019; 30:3184-3197. [DOI: 10.1093/cercor/bhz302] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 10/19/2019] [Accepted: 11/08/2019] [Indexed: 12/17/2022] Open
Abstract
Abstract
Approaches to control epilepsy, one of the most important idiopathic brain disorders, are of great importance for public health. We have previously shown that in sympathetic neurons the neuronal isoform of the serum and glucocorticoid-regulated kinase (SGK1.1) increases the M-current, a well-known target for seizure control. The effect of SGK1.1 activation on kainate-induced seizures and neuronal excitability was studied in transgenic mice that express a permanently active form of the kinase, using electroencephalogram recordings and electrophysiological measurements in hippocampal brain slices. Our results demonstrate that SGK1.1 activation leads to reduced seizure severity and lower mortality rates following status epilepticus, in an M-current–dependent manner. EEG is characterized by reduced number, shorter duration, and early termination of kainate-induced seizures in the hippocampus and cortex. Hippocampal neurons show decreased excitability associated to increased M-current, without altering basal synaptic transmission or other neuronal properties. Altogether, our results reveal a novel and selective anticonvulsant pathway that promptly terminates seizures, suggesting that SGK1.1 activation can be a potent factor to secure the brain against permanent neuronal damage associated to epilepsy.
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Affiliation(s)
- Natalia Armas-Capote
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
| | - Laura E Maglio
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
| | - Leonel Pérez-Atencio
- Unidad de Neurologia Experimental, Hospital Ramon y Cajal-IRYCIS, Madrid, 28034 Spain
| | - Elva Martin-Batista
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
| | - Antonio Reboreda
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Vigo, 36310 Spain
| | - Juan A Barios
- Systems Engineering and Automation Department, Miguel Hernandez University, Elche, 03202 Spain
| | - Guadalberto Hernandez
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
| | - Diego Alvarez de la Rosa
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
| | - José Antonio Lamas
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Vigo, 36310 Spain
| | - Luis C Barrio
- Unidad de Neurologia Experimental, Hospital Ramon y Cajal-IRYCIS, Madrid, 28034 Spain
| | - Teresa Giraldez
- Departamento de Ciencias Medicas Basicas-Fisiologia and Instituto de Tecnologías Biomedicas (ITB), Universidad de La Laguna, Tenerife, 38071 Spain
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10
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Ding X, Liang YJ, Su L, Liao FF, Fang D, Tai J, Xing GG. BDNF contributes to the neonatal incision-induced facilitation of spinal long-term potentiation and the exacerbation of incisional pain in adult rats. Neuropharmacology 2018; 137:114-132. [PMID: 29729892 DOI: 10.1016/j.neuropharm.2018.04.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 04/08/2018] [Accepted: 04/29/2018] [Indexed: 01/16/2023]
Abstract
Neonatal surgical injury exacerbates spinal microglial reactivity, modifies spinal synaptic function, leading to exaggerated pain hypersensitivity after adult repeated incision. Whether and how the alteration in microglial reactivity and synaptic plasticity are functionally related remain unclear. Previously, we and others have documented that spinal brain-derived neurotrophic factor (BDNF), secreted from microglia, contributes to long-term potentiation (LTP) in adult rodents with neuropathic pain. Here, we demonstrated that the mRNA and protein expression of spinal BDNF are significantly upregulated in adult rats subjected to neonatal incision and adult repeated incision (nIN-IN). Neonatal incision facilitates spinal LTP induced by BDNF or high frequency electrical stimulation after adult incision, including a decreased induction threshold and an increased magnitude of LTP. Coincidently, inhibition of spinal BDNF abrogates the LTP facilitation, alleviates the mechanical allodynia and thermal hyperalgesia in nIN-IN rats. By contrast, spinal application of exogenous BDNF in the adult rats with a single neonatal incision mimics the LTP facilitation and pain hypersensitivity, which have been found in nIN-IN rats. Exogenous BDNF-induced exacerbation of pain hypersensitivity could be blocked by BDNF inhibitor. In addition, blockade of microglial reactivity by intrathecal application of minocycline attenuates the elevation of BDNF and the LTP facilitation, and also, alleviates pain hypersensitivity in nIN-IN rats. In conclusion, spinal BDNF, at least partly derived from microglia, contributes to the neonatal incision-induced facilitation of spinal LTP and to the exacerbation of incisional pain in adult rats. Thus, spinal BDNF may combine the changes of microglial reactivity and synaptic plasticity in nIN-IN rats.
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Affiliation(s)
- Xu Ding
- Nutrition Research Unit, Beijing Pediatric Research Institute, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China.
| | - Ya-Jing Liang
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Peking University, Key Lab for Neuroscience, Ministry of Education of China and National Committee of Health and Family Planning of China, Peking University, Beijing 100083, China.
| | - Li Su
- Center of Medical and Health Analysis, Peking University, Beijing, China.
| | - Fei-Fei Liao
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Peking University, Key Lab for Neuroscience, Ministry of Education of China and National Committee of Health and Family Planning of China, Peking University, Beijing 100083, China.
| | - Dong Fang
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Peking University, Key Lab for Neuroscience, Ministry of Education of China and National Committee of Health and Family Planning of China, Peking University, Beijing 100083, China.
| | - Jun Tai
- Beijing Key Laboratory for Pediatric Diseases of Otolaryngology, Head and Neck Surgery, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China.
| | - Guo-Gang Xing
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Peking University, Key Lab for Neuroscience, Ministry of Education of China and National Committee of Health and Family Planning of China, Peking University, Beijing 100083, China.
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11
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Barrese V, Stott JB, Greenwood IA. KCNQ-Encoded Potassium Channels as Therapeutic Targets. Annu Rev Pharmacol Toxicol 2018; 58:625-648. [DOI: 10.1146/annurev-pharmtox-010617-052912] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | | | - Iain A. Greenwood
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, United Kingdom;, ,
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12
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Urban KR, Valentino RJ. Age- and Sex-Dependent Impact of Repeated Social Stress on Intrinsic and Synaptic Excitability of the Rat Prefrontal Cortex. Cereb Cortex 2017; 27:244-253. [PMID: 28013234 PMCID: PMC5939192 DOI: 10.1093/cercor/bhw388] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 11/12/2016] [Indexed: 11/14/2022] Open
Abstract
Stress is implicated in psychiatric illnesses that are characterized by impairments in cognitive functions that are mediated by the medial prefrontal cortex (mPFC). Because sex and age determine stress vulnerability, the effects of repeated social stress occurring during early adolescence, mid-adolescence, or adulthood on the cellular properties of male and female rat mPFC Layer V neurons in vitro were examined. Repeated resident-intruder stress produced age- and sex-specific effects on mPFC intrinsic and synaptic excitability. Mid-adolescents were particularly vulnerable to effects on intrinsic excitability. The maximum number of action potentials (APs) evoked by increasing current intensity was robustly decreased in stressed male and female mid-adolescent rats compared with age-matched controls. These effects were associated with stress-induced changes in AP half-width, amplitude, threshold, and input resistance. Social stress at all ages generally decreased synaptic excitability by decreasing the amplitude of spontaneous excitatory postsynaptic potentials. The results suggest that whereas social stress throughout life can diminish the influence of afferents driving the mPFC, social stress during mid-adolescence additionally affects intrinsic characteristics of mPFC neurons that determine excitability. The depressant effects of social stress on intrinsic and synaptic mPFC neurons may underlie its ability to affect executive functions and emotional responses, particularly during adolescence.
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Affiliation(s)
- Kimberly R. Urban
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Rita J. Valentino
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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13
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Booth CA, Brown JT, Randall AD. Neurophysiological modification of CA1 pyramidal neurons in a transgenic mouse expressing a truncated form of disrupted-in-schizophrenia 1. Eur J Neurosci 2014; 39:1074-90. [PMID: 24712988 PMCID: PMC4232873 DOI: 10.1111/ejn.12549] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 01/22/2023]
Abstract
A t(1;11) balanced chromosomal translocation transects the Disc1 gene in a large Scottish family and produces genome-wide linkage to schizophrenia and recurrent major depressive disorder. This study describes our in vitro investigations into neurophysiological function in hippocampal area CA1 of a transgenic mouse (DISC1tr) that expresses a truncated version of DISC1 designed to reproduce aspects of the genetic situation in the Scottish t(1;11) pedigree. We employed both patch-clamp and extracellular recording methods in vitro to compare intrinsic properties and synaptic function and plasticity between DISC1tr animals and wild-type littermates. Patch-clamp analysis of CA1 pyramidal neurons (CA1-PNs) revealed no genotype dependence in multiple subthreshold parameters, including resting potential, input resistance, hyperpolarization-activated ‘sag’ and resonance properties. Suprathreshold stimuli revealed no alteration to action potential (AP) waveform, although the initial rate of AP production was higher in DISC1tr mice. No difference was observed in afterhyperpolarizing potentials following trains of 5–25 APs at 50 Hz. Patch-clamp analysis of synaptic responses in the Schaffer collateral commissural (SC) pathway indicated no genotype-dependence of paired pulse facilitation, excitatory postsynaptic potential summation or AMPA/NMDA ratio. Extracellular recordings also revealed an absence of changes to SC synaptic responses and indicated input–output and short-term plasticity were also unaltered in the temporoammonic (TA) input. However, in DISC1tr mice theta burst-induced long-term potentiation was enhanced in the SC pathway but completely lost in the TA pathway. These data demonstrate that expressing a truncated form of DISC1 affects intrinsic properties of CA1-PNs and produces pathway-specific effects on long-term synaptic plasticity.
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Affiliation(s)
- Clair A Booth
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK
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14
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Li C, Huang P, Lu Q, Zhou M, Guo L, Xu X. KCNQ/Kv7 channel activator flupirtine protects against acute stress-induced impairments of spatial memory retrieval and hippocampal LTP in rats. Neuroscience 2014; 280:19-30. [PMID: 25234320 DOI: 10.1016/j.neuroscience.2014.09.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 09/03/2014] [Accepted: 09/05/2014] [Indexed: 12/17/2022]
Abstract
Spatial memory retrieval and hippocampal long-term potentiation (LTP) are impaired by stress. KCNQ/Kv7 channels are closely associated with memory and the KCNQ/Kv7 channel activator flupirtine represents neuroprotective effects. This study aims to test whether KCNQ/Kv7 channel activation prevents acute stress-induced impairments of spatial memory retrieval and hippocampal LTP. Rats were placed on an elevated platform in the middle of a bright room for 30 min to evoke acute stress. The expression of KCNQ/Kv7 subunits was analyzed at 1, 3 and 12 h after stress by Western blotting. Spatial memory was examined by the Morris water maze (MWM) and the field excitatory postsynaptic potential (fEPSP) in the hippocampal CA1 area was recorded in vivo. Acute stress transiently decreased the expression of KCNQ2 and KCNQ3 in the hippocampus. Acute stress impaired the spatial memory retrieval and hippocampal LTP, the KCNQ/Kv7 channel activator flupirtine prevented the impairments, and the protective effects of flupirtine were blocked by XE-991 (10,10-bis(4-Pyridinylmethyl)-9(10H)-anthracenone), a selective KCNQ channel blocker. Furthermore, acute stress decreased the phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser9 in the hippocampus, and flupirtine inhibited the reduction. These results suggest that the KCNQ/Kv7 channels may be a potential target for protecting both hippocampal synaptic plasticity and spatial memory retrieval from acute stress influences.
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Affiliation(s)
- C Li
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - P Huang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Q Lu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan 430030, China
| | - M Zhou
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - L Guo
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan 430030, China
| | - X Xu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan 430030, China.
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15
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Suzuki E, Okada T. Stratum oriens stimulation-evoked modulation of hippocampal long-term potentiation involves the activation of muscarinic acetylcholine receptors and the inhibition of Kv7/M potassium ion channels. Eur J Neurosci 2012; 36:1984-92. [PMID: 22639893 DOI: 10.1111/j.1460-9568.2012.08127.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Acetylcholine is considered to be an endogenous modulator of hippocampal neurotransmission and synaptic plasticity. The activation of muscarinic acetylcholine receptors (mAChRs) reportedly enhances hippocampal synaptic plasticity, which plays an important role in memory function; however, the mechanism by which it enhances synaptic plasticity remains unclear. Here, we examined the involvement of the inhibition of Kv7/M K(+) channels, which are targets of mAChR modulation, during mAChR activation-induced enhancement of long-term potentiation (LTP) at rat hippocampal Schaffer collateral (SC)-CA1 synapses. When an electrical stimulus was applied to the stratum oriens before tetanic stimulation of the SCs, the magnitude of the induced SC-CA1 synapse LTP was enhanced as compared with that induced without stratum oriens stimulation. In the presence of the mAChR antagonist atropine, tetanic stimulation induced stable LTP, but the stratum oriens stimulation-evoked enhancement of LTP was abolished. The additional application of XE991, a selective blocker of Kv7/M K(+) channels, rescued the atropine-induced inhibition of LTP enhancement. The phospholipase C (PLC) inhibitor U-73122 inhibited the stratum oriens stimulation-evoked enhancement of LTP. Application of the T/R-type voltage-dependent Ca(2+) channel (VDCC) blocker Ni(2+) abolished the stratum oriens stimulation-evoked enhancement of LTP. In addition, tetanic stimulation with preceding stratum oriens stimulation was able to induce LTP during N-methyl-d-aspartate receptor blockade. We therefore propose that stratum oriens stimulation inhibits Kv7/M K(+) channels through mAChR activation-induced PLC activation, which leads to VDCC activation, and hence causes sufficient Ca(2+) influx to enhance LTP.
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Affiliation(s)
- Etsuko Suzuki
- Department of Psychology, Faculty of Human Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
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16
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Petrovic MM, Nowacki J, Olivo V, Tsaneva-Atanasova K, Randall AD, Mellor JR. Inhibition of post-synaptic Kv7/KCNQ/M channels facilitates long-term potentiation in the hippocampus. PLoS One 2012; 7:e30402. [PMID: 22348007 PMCID: PMC3278412 DOI: 10.1371/journal.pone.0030402] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 12/20/2011] [Indexed: 12/02/2022] Open
Abstract
Activation of muscarinic acetylcholine receptors (mAChR) facilitates the induction of synaptic plasticity and enhances cognitive function. In the hippocampus, M1 mAChR on CA1 pyramidal cells inhibit both small conductance Ca2+-activated KCa2 potassium channels and voltage-activated Kv7 potassium channels. Inhibition of KCa2 channels facilitates long-term potentiation (LTP) by enhancing Ca2+calcium influx through postsynaptic NMDA receptors (NMDAR). Inhibition of Kv7 channels is also reported to facilitate LTP but the mechanism of action is unclear. Here, we show that inhibition of Kv7 channels with XE-991 facilitated LTP induced by theta burst pairing at Schaffer collateral commissural synapses in rat hippocampal slices. Similarly, negating Kv7 channel conductance using dynamic clamp methodologies also facilitated LTP. Negation of Kv7 channels by XE-991 or dynamic clamp did not enhance synaptic NMDAR activation in response to theta burst synaptic stimulation. Instead, Kv7 channel inhibition increased the amplitude and duration of the after-depolarisation following a burst of action potentials. Furthermore, the effects of XE-991 were reversed by re-introducing a Kv7-like conductance with dynamic clamp. These data reveal that Kv7 channel inhibition promotes NMDAR opening during LTP induction by enhancing depolarisation during and after bursts of postsynaptic action potentials. Thus, during the induction of LTP M1 mAChRs enhance NMDAR opening by two distinct mechanisms namely inhibition of KCa2 and Kv7 channels.
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Affiliation(s)
- Milos M. Petrovic
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- Institute of Medical Physiology, School of Medicine, Belgrade University, Beograd, Serbia
| | - Jakub Nowacki
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Valeria Olivo
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Andrew D. Randall
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Jack R. Mellor
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- * E-mail:
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17
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Santini E, Porter JT. M-type potassium channels modulate the intrinsic excitability of infralimbic neurons and regulate fear expression and extinction. J Neurosci 2010; 30:12379-86. [PMID: 20844133 PMCID: PMC3842492 DOI: 10.1523/jneurosci.1295-10.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 07/14/2010] [Accepted: 07/19/2010] [Indexed: 01/28/2023] Open
Abstract
Growing evidence indicates that the activity of infralimbic prefrontal cortex (IL) is critical for inhibiting inappropriate fear responses following extinction learning. Recently, we showed that fear conditioning and extinction alter the intrinsic excitability and bursting of IL pyramidal neurons in brain slices. IL neurons from Sprague Dawley rats expressing high fear had lower intrinsic excitability and bursting than those from rats expressing low fear, suggesting that regulating the intrinsic excitability and bursting of IL neurons would modulate fear expression. To test this, we combined patch-clamp electrophysiology, auditory fear conditioning, and IL infusions of M-type K(+) channel modulators. Patch-clamp recordings from IL neurons showed that the M-type K(+) channel blocker, XE-991, increased the number of spikes evoked by a depolarizing pulse and reduced the first interspike interval indicating enhanced bursting. To test whether pharmacological enhancement of IL excitability and bursting reduces fear expression and facilitates extinction, fear-conditioned rats were infused with XE-991 into IL before extinction training. XE-infused rats showed reduced freezing and facilitated extinction compared to vehicle-infused rats. The following day, recall of extinction memory was enhanced. Reducing IL excitability and bursting with the M-type K(+) channel agonist, flupirtine, had the opposite effect. Flupirtine reduced IL spike count and bursting in brain slices. Fear-conditioned rats infused with flupirtine into IL before extinction showed significantly higher levels of freezing, indicating that stimulation of M-channels enhanced fear expression. Our findings suggest that the intrinsic excitability and bursting of IL neurons regulate fear expression even before extinction.
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Affiliation(s)
- Edwin Santini
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ponce, Puerto Rico.
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