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Nguyen H, Glaaser IW, Slesinger PA. Direct modulation of G protein-gated inwardly rectifying potassium (GIRK) channels. Front Physiol 2024; 15:1386645. [PMID: 38903913 PMCID: PMC11187414 DOI: 10.3389/fphys.2024.1386645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/08/2024] [Indexed: 06/22/2024] Open
Abstract
Ion channels play a pivotal role in regulating cellular excitability and signal transduction processes. Among the various ion channels, G-protein-coupled inwardly rectifying potassium (GIRK) channels serve as key mediators of neurotransmission and cellular responses to extracellular signals. GIRK channels are members of the larger family of inwardly-rectifying potassium (Kir) channels. Typically, GIRK channels are activated via the direct binding of G-protein βγ subunits upon the activation of G-protein-coupled receptors (GPCRs). GIRK channel activation requires the presence of the lipid signaling molecule, phosphatidylinositol 4,5-bisphosphate (PIP2). GIRK channels are also modulated by endogenous proteins and other molecules, including RGS proteins, cholesterol, and SNX27 as well as exogenous compounds, such as alcohol. In the last decade or so, several groups have developed novel drugs and small molecules, such as ML297, GAT1508 and GiGA1, that activate GIRK channels in a G-protein independent manner. Here, we aim to provide a comprehensive overview focusing on the direct modulation of GIRK channels by G-proteins, PIP2, cholesterol, and novel modulatory compounds. These studies offer valuable insights into the underlying molecular mechanisms of channel function, and have potential implications for both basic research and therapeutic development.
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Affiliation(s)
| | | | - Paul A. Slesinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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Hleihil M, Benke D. Restoring GABA B receptor expression in the ventral tegmental area of methamphetamine addicted mice inhibits locomotor sensitization and drug seeking behavior. Front Mol Neurosci 2024; 17:1347228. [PMID: 38384279 PMCID: PMC10879384 DOI: 10.3389/fnmol.2024.1347228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/15/2024] [Indexed: 02/23/2024] Open
Abstract
Repeated exposure to psychostimulants such as methamphetamine (METH) induces neuronal adaptations in the mesocorticolimbic dopamine system, including the ventral tegmental area (VTA). These changes lead to persistently enhanced neuronal activity causing increased dopamine release and addictive phenotypes. A factor contributing to increased dopaminergic activity in this system appears to be reduced GABAB receptor-mediated neuronal inhibition in the VTA. Dephosphorylation of serine 783 (Ser783) of the GABAB2 subunit by protein phosphatase 2A (PP2A) appears to trigger the downregulation GABAB receptors in psychostimulant-addicted rodents. Therefore, preventing the interaction of GABAB receptors with PP2A using an interfering peptide is a promising strategy to restore GABAB receptor-mediated neuronal inhibition. We have previously developed an interfering peptide (PP2A-Pep) that inhibits the GABAB receptors/PP2A interaction and thereby restores receptor expression under pathological conditions. Here, we tested the hypothesis that restoration of GABAB receptor expression in the VTA of METH addicted mice reduce addictive phenotypes. We found that the expression of GABAB receptors was significantly reduced in the VTA and nucleus accumbens but not in the hippocampus and somatosensory cortex of METH-addicted mice. Infusion of PP2A-Pep into the VTA of METH-addicted mice restored GABAB receptor expression in the VTA and inhibited METH-induced locomotor sensitization as assessed in the open field test. Moreover, administration of PP2A-Pep into the VTA also reduced drug seeking behavior in the conditioned place preference test. These observations underscore the importance of VTA GABAB receptors in controlling addictive phenotypes. Furthermore, this study illustrates the value of interfering peptides targeting diseases-related protein-protein interactions as an alternative approach for a potential development of selective therapeutic interventions.
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Affiliation(s)
- Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University of Zurich, Zürich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zürich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zürich, Switzerland
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Marron Fernandez de Velasco E, Tipps ME, Haider B, Souders A, Aguado C, Rose TR, Vo BN, DeBaker MC, Luján R, Wickman K. Ethanol-Induced Suppression of G Protein-Gated Inwardly Rectifying K +-Dependent Signaling in the Basal Amygdala. Biol Psychiatry 2023; 94:863-874. [PMID: 37068702 PMCID: PMC10576835 DOI: 10.1016/j.biopsych.2023.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 04/05/2023] [Accepted: 04/05/2023] [Indexed: 04/19/2023]
Abstract
BACKGROUND The basolateral amygdala (BLA) regulates mood and associative learning and has been linked to the development and persistence of alcohol use disorder. The GABABR (gamma-aminobutyric acid B receptor) is a promising therapeutic target for alcohol use disorder, and previous work suggests that exposure to ethanol and other drugs can alter neuronal GABABR-dependent signaling. The effect of ethanol on GABABR-dependent signaling in the BLA is unknown. METHODS GABABR-dependent signaling in the mouse BLA was examined using slice electrophysiology following repeated ethanol exposure. Neuron-specific viral genetic manipulations were then used to understand the relevance of ethanol-induced neuroadaptations in the basal amygdala subregion (BA) to mood-related behavior. RESULTS The somatodendritic inhibitory effect of GABABR activation on principal neurons in the basal but not the lateral subregion of the BLA was diminished following ethanol exposure. This adaptation was attributable to the suppression of GIRK (G protein-gated inwardly rectifying K+) channel activity and was mirrored by a redistribution of GABABR and GIRK channels from the surface membrane to internal sites. While GIRK1 and GIRK2 subunits are critical for GIRK channel formation in BA principal neurons, GIRK3 is necessary for the ethanol-induced neuroadaptation. Viral suppression of GIRK channel activity in BA principal neurons from ethanol-naïve mice recapitulated some mood-related behaviors observed in C57BL/6J mice during ethanol withdrawal. CONCLUSIONS The ethanol-induced suppression of GIRK-dependent signaling in BA principal neurons contributes to some of the mood-related behaviors associated with ethanol withdrawal in mice. Approaches designed to prevent this neuroadaptation and/or strengthen GIRK-dependent signaling may prove useful for the treatment of alcohol use disorder.
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Affiliation(s)
| | - Megan E Tipps
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Bushra Haider
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Anna Souders
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Carolina Aguado
- Departmento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla La Mancha, Campus Biosanitario, La Mancha, Albacete, Spain
| | - Timothy R Rose
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Baovi N Vo
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Margot C DeBaker
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Rafael Luján
- Departmento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla La Mancha, Campus Biosanitario, La Mancha, Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
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Luo H, Marron Fernandez de Velasco E, Wickman K. Neuronal G protein-gated K + channels. Am J Physiol Cell Physiol 2022; 323:C439-C460. [PMID: 35704701 PMCID: PMC9362898 DOI: 10.1152/ajpcell.00102.2022] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to PIP2, phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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Moen JK, DeBaker MC, Myjak JE, Wickman K, Lee AM. Bidirectional sex-dependent regulation of α6 and β3 nicotinic acetylcholine receptors by protein kinase Cε. Addict Biol 2021; 26:e12954. [PMID: 32776643 DOI: 10.1111/adb.12954] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 07/10/2020] [Accepted: 07/19/2020] [Indexed: 11/29/2022]
Abstract
Nicotine and alcohol are the most commonly abused substances worldwide and are frequently coabused. Nicotinic acetylcholine receptors (nAChRs) containing the α6 and β3 subunits are expressed in neural reward circuits and are critical for nicotine and alcohol reward. nAChRs are dynamically regulated by signaling molecules such as protein kinase C epsilon (PKCε), which impact transcription of α6 and β3 subunit mRNA (Chrna6 and Chrnb3, respectively). Previous work found decreased expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain of male PKCε-/- mice, who also consume less nicotine and alcohol compared with wild-type (WT) littermates. Using RT-qPCR, we show that female PKCε-/- mice have higher expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain, which functionally impacts nAChR-dependent behavior as female but not male PKCε-/- mice exhibit locomotor hypersensitivity to low-dose (0.25 mg/kg i.p.) nicotine. Female PKCε-/- mice show no differences in alcohol-induced sedation in the loss-of-righting reflex assay (4.0 g/kg i.p.) compared with WT littermates, whereas male PKCε-/- mice have enhanced sedation compared with WT mice. Female PKCε-/- mice also show reduced immobility time in response to varenicline (1.0 mg/kg i.p.) compared with WT littermates in the tail suspension test, and this effect was absent in male mice. Additionally, we found that female PKCε-/- mice show altered alcohol and nicotine consumption patterns in chronic voluntary two-bottle choice assays. Our data reveal a bidirectional effect of sex in the transcriptional regulation of nicotinic receptors by PKCε, highlighting the importance of studying both sexes in preclinical animal models.
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Affiliation(s)
- Janna K. Moen
- Graduate Program in Neuroscience University of Minnesota Minneapolis Minnesota USA
| | - Margot C. DeBaker
- Graduate Program in Neuroscience University of Minnesota Minneapolis Minnesota USA
| | - Julia E. Myjak
- Department of Pharmacology University of Minnesota Minneapolis Minnesota USA
| | - Kevin Wickman
- Graduate Program in Neuroscience University of Minnesota Minneapolis Minnesota USA
- Department of Pharmacology University of Minnesota Minneapolis Minnesota USA
| | - Anna M. Lee
- Graduate Program in Neuroscience University of Minnesota Minneapolis Minnesota USA
- Department of Pharmacology University of Minnesota Minneapolis Minnesota USA
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Differential Impact of Inhibitory G-Protein Signaling Pathways in Ventral Tegmental Area Dopamine Neurons on Behavioral Sensitivity to Cocaine and Morphine. eNeuro 2021; 8:ENEURO.0081-21.2021. [PMID: 33707203 PMCID: PMC8114902 DOI: 10.1523/eneuro.0081-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 03/03/2021] [Indexed: 12/21/2022] Open
Abstract
Drugs of abuse engage overlapping but distinct molecular and cellular mechanisms to enhance dopamine (DA) signaling in the mesocorticolimbic circuitry. DA neurons of the ventral tegmental area (VTA) are key substrates of drugs of abuse and have been implicated in addiction-related behaviors. Enhanced VTA DA neurotransmission evoked by drugs of abuse can engage inhibitory G-protein-dependent feedback pathways, mediated by GABAB receptors (GABABRs) and D2 DA receptors (D2Rs). Chemogenetic inhibition of VTA DA neurons potently suppressed baseline motor activity, as well as the motor-stimulatory effect of cocaine and morphine, confirming the critical influence of VTA DA neurons and inhibitory G-protein signaling in these neurons on this addiction-related behavior. To resolve the relative influence of GABABR-dependent and D2R-dependent signaling pathways in VTA DA neurons on behavioral sensitivity to drugs of abuse, we developed a neuron-specific viral CRISPR/Cas9 approach to ablate D2R and GABABR in VTA DA neurons. Ablation of GABABR or D2R did not impact baseline physiological properties or excitability of VTA DA neurons, but it did preclude the direct somatodendritic inhibitory influence of GABABR or D2R activation. D2R ablation potentiated the motor-stimulatory effect of cocaine in male and female mice, whereas GABABR ablation selectively potentiated cocaine-induced activity in male subjects only. Neither D2R nor GABABR ablation impacted morphine-induced motor activity. Collectively, our data show that cocaine and morphine differ in the extent to which they engage inhibitory G-protein-dependent feedback pathways in VTA DA neurons and highlight key sex differences that may impact susceptibility to various facets of addiction.
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Therapeutic potential of targeting G protein-gated inwardly rectifying potassium (GIRK) channels in the central nervous system. Pharmacol Ther 2021; 223:107808. [PMID: 33476640 DOI: 10.1016/j.pharmthera.2021.107808] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/05/2021] [Indexed: 12/15/2022]
Abstract
G protein-gated inwardly rectifying potassium channels (Kir3/GirK) are important for maintaining resting membrane potential, cell excitability and inhibitory neurotransmission. Coupled to numerous G protein-coupled receptors (GPCRs), they mediate the effects of many neurotransmitters, neuromodulators and hormones contributing to the general homeostasis and particular synaptic plasticity processes, learning, memory and pain signaling. A growing number of behavioral and genetic studies suggest a critical role for the appropriate functioning of the central nervous system, as well as their involvement in many neurologic and psychiatric conditions, such as neurodegenerative diseases, mood disorders, attention deficit hyperactivity disorder, schizophrenia, epilepsy, alcoholism and drug addiction. Hence, GirK channels emerge as a very promising tool to be targeted in the current scenario where these conditions already are or will become a global public health problem. This review examines recent findings on the physiology, function, dysfunction, and pharmacology of GirK channels in the central nervous system and highlights the relevance of GirK channels as a worthful potential target to improve therapies for related diseases.
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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Li X, Slesinger PA. GABA B Receptors and Drug Addiction: Psychostimulants and Other Drugs of Abuse. Curr Top Behav Neurosci 2020; 52:119-155. [PMID: 33442842 DOI: 10.1007/7854_2020_187] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Metabotropic GABAB receptors (GABABRs) mediate slow inhibition and modulate synaptic plasticity throughout the brain. Dysfunction of GABABRs has been associated with psychiatric illnesses and addiction. Drugs of abuse alter GABAB receptor (GABABR) signaling in multiple brain regions, which partly contributes to the development of drug addiction. Recently, GABABR ligands and positive allosteric modulators (PAMs) have been shown to attenuate the initial rewarding effect of addictive substances, inhibit seeking and taking of these drugs, and in some cases, ameliorate drug withdrawal symptoms. The majority of the anti-addiction effects seen with GABABR modulation can be localized to ventral tegmental area (VTA) dopamine neurons, which receive complex inhibitory and excitatory inputs that are modified by drugs of abuse. Preclinical research suggests that GABABR PAMs are emerging as promising candidates for the treatment of drug addiction. Clinical studies on drug dependence have shown positive results with GABABR ligands but more are needed, and compounds with better pharmacokinetics and fewer side effects are critically needed.
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Affiliation(s)
- Xiaofan Li
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Paul A Slesinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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Jayanthi S, Torres OV, Ladenheim B, Cadet JL. A Single Prior Injection of Methamphetamine Enhances Methamphetamine Self-Administration (SA) and Blocks SA-Induced Changes in DNA Methylation and mRNA Expression of Potassium Channels in the Rat Nucleus Accumbens. Mol Neurobiol 2019; 57:1459-1472. [PMID: 31758400 PMCID: PMC7060962 DOI: 10.1007/s12035-019-01830-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 11/01/2019] [Indexed: 12/27/2022]
Abstract
The transition from occasional to escalated psychostimulant use is accelerated by prior drug exposure. These behavioral observations may be related to long-lasting transcriptional and/or epigenetic changes induced by the drug pre-exposure. Herein, we investigated if a single methamphetamine (METH) injection would enhance METH self-administration (SA) and impact any METH SA-induced epigenetic or transcriptional alterations. We thus injected a single METH dose (10 mg/kg) or saline to rats before training them to self-administer METH or saline. There were three experimental groups in SA experiments: (1) a single saline injection followed by saline SA (SS); (2) a single saline injection followed by METH SA (SM); and (3) a single METH injection followed by METH SA (MM). METH-pretreated rats escalated METH SA earlier and took more METH than saline-pretreated animals. Both groups showed similar incubation of cue-induced METH craving. Because compulsive METH takers and METH-abstinent rats show differences in potassium (K+) channel mRNA levels in their nucleus accumbens (NAc), we wondered if K+ channel expression might also help to distinguish between SM and MM groups. We found increases in mRNA and protein expression of shaker-related voltage-gated K+ channels (Kv1: Kcna1, Kcna3, and Kcna6) and calcium-activated K+ channels (Kcnn1) in the SM compared to MM rats. SM rats also showed decreased DNA methylation at the CpG-rich sites near the promoter region of Kcna1, Kcna3 and Kcnn1 genes in comparison to MM rats. Together, these results provide additional evidence for potentially using K+ channels as therapeutic targets against METH use disorder.
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Affiliation(s)
- Subramaniam Jayanthi
- Molecular Neuropsychiatry Research Branch, Intramural Research Program, NIDA/NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD, 21224, USA
| | - Oscar V Torres
- Department of Behavioral Sciences, San Diego Mesa College, San Diego, CA, USA
| | - Bruce Ladenheim
- Molecular Neuropsychiatry Research Branch, Intramural Research Program, NIDA/NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD, 21224, USA
| | - Jean Lud Cadet
- Molecular Neuropsychiatry Research Branch, Intramural Research Program, NIDA/NIH/DHHS, 251 Bayview Boulevard, Baltimore, MD, 21224, USA.
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Miguel E, Vekovischeva O, Kuokkanen K, Vesajoki M, Paasikoski N, Kaskinoro J, Myllymäki M, Lainiola M, Janhunen SK, Hyytiä P, Linden A, Korpi ER. GABA B receptor positive allosteric modulators with different efficacies affect neuroadaptation to and self-administration of alcohol and cocaine. Addict Biol 2019; 24:1191-1203. [PMID: 30421860 DOI: 10.1111/adb.12688] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 09/28/2018] [Accepted: 10/04/2018] [Indexed: 01/14/2023]
Abstract
Drugs of abuse induce widespread synaptic adaptations in the mesolimbic dopamine (DA) neurons. Such drug-induced neuroadaptations may constitute an initial cellular mechanism eventually leading to compulsive drug-seeking behavior. To evaluate the impact of GABAB receptors on addiction-related persistent neuroplasticity, we tested the ability of orthosteric agonist baclofen and two positive allosteric modulators (PAMs) of GABAB receptors to suppress neuroadaptations in the ventral tegmental area (VTA) and reward-related behaviors induced by ethanol and cocaine. A novel compound (S)-1-(5-fluoro-2,3-dihydro-1H-inden-2-yl)-4-methyl-6,7,8,9-tetrahydro-[1,2,4]triazolo[4,3-a]quinazolin-5(4H)-one (ORM-27669) was found to be a GABAB PAM of low efficacy as agonist, whereas the reference compound (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF) had a different allosteric profile being a more potent PAM in the calcium-based assay and an agonist, coupled with potent PAM activity, in the [35 S] GTPγS binding assay in rat and human recombinant receptors. Using autoradiography, the high-efficacy rac-BHFF and the low-efficacy ORM-27669 potentiated the effects of baclofen on [35 S] GTPγS binding with identical brain regional distribution. Treatment of mice with baclofen, rac-BHFF, or ORM-27669 failed to induce glutamate receptor neuroplasticity in the VTA DA neurons. Pretreatment with rac-BHFF at non-sedative doses effectively reversed both ethanol- and cocaine-induced plasticity and attenuated cocaine i.v. self-administration and ethanol drinking. Pretreatment with ORM-27669 only reversed ethanol-induced neuroplasticity and attenuated ethanol drinking but had no effects on cocaine-induced neuroplasticity or self-administration. These findings encourage further investigation of GABAB receptor PAMs with different efficacies in addiction models to develop novel treatment strategies for drug addiction.
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Affiliation(s)
- Elena Miguel
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | - Olga Vekovischeva
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | - Katja Kuokkanen
- Research and Development, Orion Pharma, Orion Corporation Finland
| | - Marja Vesajoki
- Research and Development, Orion Pharma, Orion Corporation Finland
| | - Nelli Paasikoski
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | - Janne Kaskinoro
- Research and Development, Orion Pharma, Orion Corporation Finland
| | - Mikko Myllymäki
- Research and Development, Orion Pharma, Orion Corporation Finland
| | - Mira Lainiola
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | | | - Petri Hyytiä
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | - Anni‐Maija Linden
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
| | - Esa R. Korpi
- Department of Pharmacology, Faculty of MedicineUniversity of Helsinki Finland
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Ma Z, Gao F, Larsen B, Gao M, Luo Z, Chen D, Ma X, Qiu S, Zhou Y, Xie J, Xi ZX, Wu J. Mechanisms of cannabinoid CB 2 receptor-mediated reduction of dopamine neuronal excitability in mouse ventral tegmental area. EBioMedicine 2019; 42:225-237. [PMID: 30952618 PMCID: PMC6491419 DOI: 10.1016/j.ebiom.2019.03.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 02/24/2019] [Accepted: 03/14/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND We have recently reported that activation of cannabinoid type 2 receptors (CB2Rs) reduces dopamine (DA) neuron excitability in mouse ventral tegmental area (VTA). Here, we elucidate the underlying mechanisms. METHODS Patch-clamp recordings were performed in mouse VTA slices and dissociated single VTA DA neurons. FINDINGS Using cell-attached recording in VTA slices, bath-application of CB2R agonists (JWH133 or five other CB2R agonists) significantly reduced VTA DA neuron action potential (AP) firing rate. Under the patch-clamp whole-cell recording model, JWH133 (10 μM) mildly reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs) but not miniature inhibitory postsynaptic currents (mIPSCs). JWH133 also did not alter evoked EPSCs or IPSCs. In freshly dissociated VTA DA neurons, JWH133 reduced AP firing rate, delayed AP initiation and enhanced AP after-hyperpolarization. In voltage-clamp recordings, JWH133 (1 μM) enhanced M-type K+ currents and this effect was absent in CB2-/- mice and abolished by co-administration of a selective CB2R antagonist (10 μM, AM630). CB2R-mediated inhibition in VTA DA neuron firing can be mimicked by M-current opener (10 μM retigabine) and blocked by M-current blocker (30 μM XE991). In addition, enhancement of neuronal cAMP by forskolin (10 μM) reduced M-current and increased DA neuron firing rate. Finally, pharmacological block of synaptic transmission by NBQX (10 μM), D-APV (50 μM) and picrotoxin (100 μM) in VTA slices failed to prevent CB2R-mediated inhibition, while intracellular infusion of guanosine 5'-O-2-thiodiphosphate (600 μM, GDP-β-S) through recording electrode to block postsynaptic G-protein function prevented JWH133-induced reduction in AP firing. INTERPRETATION Our results suggest that CB2Rs modulate VTA DA neuron excitability mainly through an intrinsic mechanism, including a CB2R-mediated reduction of intracellular cAMP, and in turn enhancement of M-type K+ currents. FUND: This research was supported by the Barrow Neuroscience Foundation, the BNI-BMS Seed Fund, and CNSF (81771437).
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Affiliation(s)
- Zegang Ma
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders, Shandong Provincial Collaborative Innovation Center for Neurodegenerative Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao 266071, China; Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | - Fenfei Gao
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong 210854, China; Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | - Brett Larsen
- Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA; Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Ming Gao
- Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | - Zhihua Luo
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong 210854, China
| | - Dejie Chen
- Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA; Department of Neurology, Yunfu People's Hospital, Yunfu, Guangdong 527300, China
| | - Xiaokuang Ma
- Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA; Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong 210854, China; Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Shenfeng Qiu
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Yu Zhou
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders, Shandong Provincial Collaborative Innovation Center for Neurodegenerative Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao 266071, China
| | - Junxia Xie
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders, Shandong Provincial Collaborative Innovation Center for Neurodegenerative Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao 266071, China
| | - Zheng-Xiong Xi
- Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD 21224, USA
| | - Jie Wu
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders, Shandong Provincial Collaborative Innovation Center for Neurodegenerative Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao 266071, China; Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA; Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong 210854, China; Department of Neurology, Yunfu People's Hospital, Yunfu, Guangdong 527300, China.
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GIRK Channel Activity in Dopamine Neurons of the Ventral Tegmental Area Bidirectionally Regulates Behavioral Sensitivity to Cocaine. J Neurosci 2019; 39:3600-3610. [PMID: 30837265 DOI: 10.1523/jneurosci.3101-18.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/17/2019] [Accepted: 02/22/2019] [Indexed: 12/19/2022] Open
Abstract
Dopamine (DA) neurons of the VTA have been widely implicated in the cellular and behavioral responses to drugs of abuse. Inhibitory G protein signaling mediated by GABAB receptors (GABABRs) and D2 DA receptors (D2Rs) regulates the excitability of VTA DA neurons, DA neurotransmission, and behaviors modulated by DA. Most of the somatodendritic inhibitory effect of GABABR and D2R activation on DA neurons reflects the activation of G protein-gated inwardly rectifying K+ (GIRK) channels. Furthermore, GIRK-dependent signaling in VTA DA neurons can be weakened by exposure to psychostimulants and strengthened by phasic DA neuron firing. The objective of this study was to determine how the strength of GIRK channel activity in VTA DA neurons influences sensitivity to cocaine. We used a Cre-dependent viral strategy to overexpress the individual GIRK channel subunits in VTA DA neurons of male and female adult mice, leading to enhancement (GIRK2) or suppression (GIRK3) of GIRK channel activity. Overexpression of GIRK3 decreased somatodendritic GABABR- and D2R-dependent signaling and increased cocaine-induced locomotor activity, whereas overexpression of GIRK2 increased GABABR-dependent signaling and decreased cocaine-induced locomotion. Neither manipulation impacted anxiety- or depression-related behavior, despite the link between such behaviors and DA signaling. Together, these data show that behavioral sensitivity to cocaine in mice is inversely proportional to the strength of GIRK channel activity in VTA DA neurons and suggest that direct activators of the unique VTA DA neuron GIRK channel subtype (GIRK2/GIRK3 heteromer) could represent a promising therapeutic target for treatment of addiction.SIGNIFICANCE STATEMENT Inhibitory G protein signaling in dopamine (DA) neurons, including that mediated by G protein-gated inwardly rectifying K+ (GIRK) channels, has been implicated in behavioral sensitivity to cocaine. Here, we used a viral approach to bidirectionally manipulate GIRK channel activity in DA neurons of the VTA. We found that decreasing GIRK channel activity in VTA DA neurons increased behavioral sensitivity to cocaine, whereas increasing GIRK channel activity decreased behavioral sensitivity to cocaine. These manipulations did not alter anxiety- or depression-related behaviors. These data highlight the unique GIRK channel subtype in VTA DA neurons as a possible therapeutic target for addiction.
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Groos D, Zheng F, Rauh M, Quinger B, Kornhuber J, Müller CP, Alzheimer C. Chronic antipsychotic treatment targets GIRK current suppression, loss of long-term synaptic depression and behavioural sensitization in a mouse model of amphetamine psychosis. J Psychopharmacol 2018; 33:269881118812235. [PMID: 30488738 DOI: 10.1177/0269881118812235] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND: Antipsychotic drugs (APDs) are the mainstay of the pharmacological treatment of psychotic disorders like schizophrenia. While the clinical efficacy of APDs has long since been established, the neurobiological mechanisms underlying their therapeutic benefits are still not well understood. METHODS: Here, we used an escalating amphetamine regimen to induce a psychosis-like state in mice. To achieve clinically relevant drug concentrations in amphetamine-pretreated mice, the typical APD haloperidol or the atypical APD olanzapine were chronically administered via subcutaneously implanted osmotic mini-pumps. RESULTS: Demonstrating their therapeutic efficacy, both drugs dampened amphetamine-induced hyperlocomotion and restored normal behaviour in the light-induced activity test. Whole-cell recordings from dopaminergic neurons of the ventral tegmental area (VTA) in ex vivo brain slices revealed two pronounced aberrations associated with the psychosis-like state: Strongly enhanced spontaneous firing and a substantial loss of G protein-gated inwardly rectifying potassium (GIRK) current upon activation of GABAB receptors with baclofen. Chronic haloperidol and olanzapine restored normal firing and partially rescued the GIRK current response to baclofen. In ex vivo slices containing the nucleus accumbens, which receives a dopaminergic projection from the VTA, abrogation of long-term synaptic depression (LTD) and enhanced excitatory drive onto medium spiny neurons were identified as synaptic consequences of amphetamine-induced psychosis. Again, both alterations proved amenable to chronic APD treatment. CONCLUSION: Our data provide evidence for aberrant neuronal function and plasticity in the mesolimbic dopamine system during an induced psychotic state and identify these alterations as targets of chronic APD treatment.
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Affiliation(s)
- Dominik Groos
- 1 Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Fang Zheng
- 1 Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Manfred Rauh
- 2 Department of Pediatrics and Adolescent Medicine, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Benedikt Quinger
- 3 Department of Psychiatry and Psychotherapy, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Johannes Kornhuber
- 3 Department of Psychiatry and Psychotherapy, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Christian P Müller
- 3 Department of Psychiatry and Psychotherapy, Universitätsklinikum Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Christian Alzheimer
- 1 Institute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
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15
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GIRK currents in VTA dopamine neurons control the sensitivity of mice to cocaine-induced locomotor sensitization. Proc Natl Acad Sci U S A 2018; 115:E9479-E9488. [PMID: 30228121 PMCID: PMC6176583 DOI: 10.1073/pnas.1807788115] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
GABABR-dependent activation of G protein-gated inwardly rectifying potassium channels (GIRK or KIR3) provides a well-known source of inhibition in the brain, but the details on how this important inhibitory pathway affects neural circuits are lacking. We used sorting nexin 27 (SNX27), an endosomal adaptor protein that associates with GIRK2c and GIRK3 subunits, to probe the role of GIRK channels in reward circuits. A conditional knockout of SNX27 in both substantia nigra pars compacta and ventral tegmental area (VTA) dopamine neurons leads to markedly smaller GABABR- and dopamine D2R-activated GIRK currents, as well as to suprasensitivity to cocaine-induced locomotor sensitization. Expression of the SNX27-insensitive GIRK2a subunit in SNX27-deficient VTA dopamine neurons restored GIRK currents and GABABR-dependent inhibition of spike firing, while also resetting the mouse's sensitivity to cocaine-dependent sensitization. These results establish a link between slow inhibition mediated by GIRK channels in VTA dopamine neurons and cocaine addiction, revealing a therapeutic target for treating addiction.
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16
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Francis TC, Gantz SC, Moussawi K, Bonci A. Synaptic and intrinsic plasticity in the ventral tegmental area after chronic cocaine. Curr Opin Neurobiol 2018; 54:66-72. [PMID: 30237117 PMCID: PMC10131346 DOI: 10.1016/j.conb.2018.08.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 08/24/2018] [Accepted: 08/28/2018] [Indexed: 11/28/2022]
Abstract
Cocaine exposure induces persistent changes in synaptic transmission and intrinsic properties of ventral tegmental area (VTA) dopamine neurons. Despite significant progress in understanding cocaine-induced plasticity, an effective treatment of cocaine addiction is lacking. Chronic cocaine potentiates excitatory and alters inhibitory transmission to dopamine neurons, induces dopamine neuron hyperexcitability, and reduces dopamine release in projection areas. Understanding how intrinsic and synaptic plasticity interact to control dopamine neuron firing and dopamine release could prove useful in the development of new therapeutics. In this review, we examine recent literature discussing cocaine-induced plasticity in the VTA and highlight potential therapeutic interventions.
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Affiliation(s)
- Tanner Chase Francis
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, US National Institutes of Health, Baltimore, MD 21224, USA
| | - Stephanie C Gantz
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, US National Institutes of Health, Baltimore, MD 21224, USA
| | - Khaled Moussawi
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, US National Institutes of Health, Baltimore, MD 21224, USA; Department of Neurology, Johns Hopkins Medicine, Baltimore, MD 21205, USA
| | - Antonello Bonci
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, US National Institutes of Health, Baltimore, MD 21224, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA; Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Neuroscience, Georgetown University Medical Center, School of Medicine, Washington, DC, USA; Department of Psychiatry, University of Maryland, School of Medicine, Baltimore, MD, USA.
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17
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Dehkordi O, Rose JE, Millis RM, Dalivand MM, Johnson SM. GABAergic Neurons as Putative Neurochemical Substrate Mediating Aversive Effects of Nicotine. ACTA ACUST UNITED AC 2018; 6. [PMID: 30009210 PMCID: PMC6042868 DOI: 10.4172/2329-6488.1000312] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nicotine, the main addictive component of tobacco smoke, has both rewarding and aversive properties. Recent studies have suggested that GABAergic neurons, one of the main neurochemical components of the reward-addiction circuitry, may also play a role in the aversive responses to nicotine. In the present study of transgenic mice expressing Green Fluorescent Protein (GFP) in Glutamate Decarboxylase 67 (GAD67) neurons, we hypothesized that a subpopulation of GABAergic neurons in the Ventral Tegmental Area (VTA) are the targets of aversive doses of nicotine in the CNS. We tested this hypothesis using c-Fos immunohistochemical techniques to identify GAD67-GFP positive cells within the VTA, that are activated by a single intraperitoneal (i.p.) injection of a low (40 ug/kg) or a high (2 mg/kg) dose of nicotine. We also assessed the anatomical location of GAD67-GFP positive cells with respect to tyrosine hydroxylase (TH) Immunoreactive (IR) dopaminergic cells in VTA. Consistent with our previous studies low- and high-dose nicotine both induced c-Fos activation of various intensities at multiple sites in VTA. Double labeling of c-Fos activated cells with GAD67-GFP positive cells identified a subpopulation of GABAergic neurons in Substantia Nigra Compact part Medial tier (SNCM) that were activated by high- but not by low-dose nicotine. Of 217 GABAergic cells counted at this site, 48.9% exhibited nicotine induced c-fos immunoreactivity. GAD67-GFP positive cells in other regions of VTA were not activated by the nicotine doses tested. Double labeling of GAD67-GFP positive cells with TH IR cells showed that the GABAergic neurons that were activated by high-dose nicotine were located in close proximity to the dopaminergic neurons of substantia nigra compact part and VTA. Dose-dependent activation of GAD67-GFP positive neurons in SNCM, by a nicotine dose known to produce aversive responses, implies that GABAergic neurons at these sites may be an important component of the nicotine aversive circuitry.
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Affiliation(s)
- Ozra Dehkordi
- Department of Neurology, Howard University Hospital Washington D.C. 20060, United States.,Department of Physiology & Biophysics, Howard University College of Medicine Washington, D.C. 20059, United States
| | - Jed E Rose
- Department of Psychiatry, Duke University Medical Center, Durham, NC 27705, United States
| | - Richard M Millis
- Department of Medical Physiology, American University of Antigua College of Medicine, Antigua & Barbuda, West Indies
| | | | - Shereé M Johnson
- Department of Physiology & Biophysics, Howard University College of Medicine Washington, D.C. 20059, United States
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18
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Cocaine-induced locomotor sensitization associates with slow oscillatory firing of neurons in the ventral tegmental area. Sci Rep 2018; 8:3274. [PMID: 29459754 PMCID: PMC5818474 DOI: 10.1038/s41598-018-21592-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 02/05/2018] [Indexed: 11/22/2022] Open
Abstract
The initiation of psychostimulant sensitization depends on the mesocorticolimbic dopamine (DA) system. Although many cellular adaptations has been reported to be associated with this addictive behavior, the overall influence of these adaptations on the network regulation of DA neurons has not been established. Here, we profile a network-driven slow oscillation (SO) in the firing activity of ventral tegmental area (VTA) putative DA and non-DA neurons and their correlation with locomotor sensitization induced by repeated administration of cocaine. One day after the last cocaine injection, the power of SO (Pso) significantly increased both in DA and non-DA neurons. Interestingly, the Pso in DA neurons was positively correlated, while Pso in non-DA neurons was negatively correlated with the level of locomotor sensitization. On the other hand, the firing rates of DA and non-DA neurons were both elevated, but none exhibited any correlation with the level of sensitization. Fourteen days after the last injection, the Pso of DA neurons dissipated but still positively correlated with the level of sensitization. In contrast, the Pso in non-DA neurons lost correlation with locomotor sensitization. These results suggest that cocaine-induced locomotor sensitization is associated with long-term network adaptation in DA system and that DA and non-DA neurons may corporately facilitate/hamper the initiation of locomotor sensitization.
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19
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Gantz SC, Ford CP, Morikawa H, Williams JT. The Evolving Understanding of Dopamine Neurons in the Substantia Nigra and Ventral Tegmental Area. Annu Rev Physiol 2018; 80:219-241. [PMID: 28938084 DOI: 10.1146/annurev-physiol-021317-121615] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In recent years, the population of neurons in the ventral tegmental area (VTA) and substantia nigra (SN) has been examined at multiple levels. The results indicate that the projections, neurochemistry, and receptor and ion channel expression in this cell population vary widely. This review centers on the intrinsic properties and synaptic regulation that control the activity of dopamine neurons. Although all dopamine neurons fire action potentials in a pacemaker pattern in the absence of synaptic input, the intrinsic properties that underlie this activity differ considerably. Likewise, the transition into a burst/pause pattern results from combinations of intrinsic ion conductances, inhibitory and excitatory synaptic inputs that differ among this cell population. Finally, synaptic plasticity is a key regulator of the rate and pattern of activity in different groups of dopamine neurons. Through these fundamental properties, the activity of dopamine neurons is regulated and underlies the wide-ranging functions that have been attributed to dopamine.
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Affiliation(s)
- Stephanie C Gantz
- Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland 21224, USA
| | - Christopher P Ford
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Hitoshi Morikawa
- Department of Neuroscience and Waggoner Center for Alcohol and Addiction Research, University of Texas, Austin, Texas 78712, USA
| | - John T Williams
- Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97239, USA;
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20
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Kramer PF, Williams JT. Calcium Release from Stores Inhibits GIRK. Cell Rep 2017; 17:3246-3255. [PMID: 28009293 DOI: 10.1016/j.celrep.2016.11.076] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 11/02/2016] [Accepted: 11/24/2016] [Indexed: 12/17/2022] Open
Abstract
Synaptic transmission is mediated by ionotropic and metabotropic receptors that together regulate the rate and pattern of action potential firing. Metabotropic receptors can activate ion channels and modulate other receptors and channels. The present paper examines the interaction between group 1 mGluR-mediated calcium release from stores and GABAB/D2-mediated GIRK currents in rat dopamine neurons of the Substantia Nigra. Transient activation of mGluRs decreased the GIRK current evoked by GABAB and D2 receptors, although less efficaciously for D2. The mGluR-induced inhibition of GIRK current peaked in 1 s and recovered to baseline after 5 s. The inhibition was dependent on release of calcium from stores, was larger for transient than for tonic currents, and was unaffected by inhibitors of PLC, PKC, PLA2, or calmodulin. This inhibition of GABAB IPSCs through release of calcium from stores is a postsynaptic mechanism that may broadly reduce GIRK-dependent inhibition of many central neurons.
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Affiliation(s)
- Paul F Kramer
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - John T Williams
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
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21
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Rifkin RA, Moss SJ, Slesinger PA. G Protein-Gated Potassium Channels: A Link to Drug Addiction. Trends Pharmacol Sci 2017; 38:378-392. [PMID: 28188005 DOI: 10.1016/j.tips.2017.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/08/2017] [Accepted: 01/10/2017] [Indexed: 11/29/2022]
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels are regulators of neuronal excitability in the brain. Knockout mice lacking GIRK channels display altered behavioral responses to multiple addictive drugs, implicating GIRK channels in addictive behaviors. Here, we review the effects of GIRK subunit deletions on the behavioral response to psychostimulants, such as cocaine and methamphetamine. Additionally, exposure of mice to psychostimulants produces alterations in the surface expression of GIRK channels in multiple types of neurons within the reward system of the brain. Thus, we compare the subcellular mechanisms by which drug exposure appears to alter GIRK expression in multiple cell types and provide an outlook on future studies examining the role of GIRK channels in addiction. A greater understanding of how GIRK channels are regulated by addictive drugs may enable the development of therapies to prevent or treat drug abuse.
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Affiliation(s)
- Robert A Rifkin
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Medical Scientist Training Program, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Stephen J Moss
- Dept of Neuroscience, Tufts University School of Medicine, Boston, MA 02155, USA; Dept of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
| | - Paul A Slesinger
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA.
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22
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McCall NM, Kotecki L, Dominguez-Lopez S, Marron Fernandez de Velasco E, Carlblom N, Sharpe AL, Beckstead MJ, Wickman K. Selective Ablation of GIRK Channels in Dopamine Neurons Alters Behavioral Effects of Cocaine in Mice. Neuropsychopharmacology 2017; 42:707-715. [PMID: 27468917 PMCID: PMC5240170 DOI: 10.1038/npp.2016.138] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 07/23/2016] [Accepted: 07/25/2016] [Indexed: 12/20/2022]
Abstract
The increase in dopamine (DA) neurotransmission stimulated by in vivo cocaine exposure is tempered by G protein-dependent inhibitory feedback mechanisms in DA neurons of the ventral tegmental area (VTA). G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels mediate the direct inhibitory effect of GABAB receptor (GABABR) and D2 DA receptor (D2R) activation in VTA DA neurons. Here we examined the effect of the DA neuron-specific loss of GIRK channels on D2R-dependent regulation of VTA DA neuron excitability and on cocaine-induced, reward-related behaviors. Selective ablation of Girk2 in DA neurons did not alter the baseline excitability of VTA DA neurons but significantly reduced the magnitude of D2R-dependent inhibitory somatodendritic currents and blunted the impact of D2R activation on spontaneous activity and neuronal excitability. Mice lacking GIRK channels in DA neurons exhibited increased locomotor activation in response to acute cocaine administration and an altered locomotor sensitization profile, as well as increased responding for and intake of cocaine in an intravenous self-administration test. These mice, however, showed unaltered cocaine-induced conditioned place preference. Collectively, our data suggest that feedback inhibition to VTA DA neurons, mediated by GIRK channel activation, tempers the locomotor stimulatory effect of cocaine while also modulating the reinforcing effect of cocaine in an operant-based self-administration task.
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Affiliation(s)
- Nora M McCall
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Lydia Kotecki
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Sergio Dominguez-Lopez
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | | | - Nicholas Carlblom
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Amanda L Sharpe
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA,Feik School of Pharmacy, University of the Incarnate Word, San Antonio, TX, USA
| | - Michael J Beckstead
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA,Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street S.E., Minneapolis, MN 55455, USA, Tel: +1 612 624 5966, Fax: +1 612 625 8408, E-mail:
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23
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Marron Fernandez de Velasco E, Carlblom N, Xia Z, Wickman K. Suppression of inhibitory G protein signaling in forebrain pyramidal neurons triggers plasticity of glutamatergic neurotransmission in the nucleus accumbens core. Neuropharmacology 2017; 117:33-40. [PMID: 28131769 DOI: 10.1016/j.neuropharm.2017.01.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 01/13/2017] [Accepted: 01/23/2017] [Indexed: 12/30/2022]
Abstract
Cocaine and other drugs of abuse trigger long-lasting adaptations in excitatory and inhibitory neurotransmission in the mesocorticolimbic system, and this plasticity has been implicated in several key facets of drug addiction. For example, glutamatergic neurotransmission mediated by AMPA receptors (AMPAR) is strengthened in medium spiny neurons (MSNs) in the NAc core and shell during withdrawal following repeated in vivo cocaine administration. Repeated cocaine administration also suppresses inhibitory signaling mediated by G protein-gated inwardly rectifying K+ (GIRK) channels in pyramidal neurons of the prelimbic cortex, an important source of glutamatergic input to the NAc core that has been implicated in cocaine-seeking and behavioral sensitization. Here, we tested the hypothesis that suppression of GIRK channel activity in forebrain pyramidal neurons can promote plasticity of glutamatergic signaling in MSNs. Using novel conditional knockout mouse lines, we report that GIRK channel ablation in forebrain pyramidal neurons is sufficient to enhance AMPAR-dependent neurotransmission in D1R-expressing MSNs in the NAc core, while also increasing motor-stimulatory responses to cocaine administration. A similar increase in AMPAR-dependent signaling was seen in both D1R- and D2R-expressing MSNs in the NAc core during withdrawal from repeated cocaine administration in normal mice. Collectively, these data are consistent with the premise that the cocaine-induced suppression of GIRK-dependent signaling in glutamatergic inputs to the NAc core contributes to some of the electrophysiological and behavioral hallmarks associated with repeated cocaine administration.
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Affiliation(s)
| | - Nicholas Carlblom
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, United States
| | - Zhilian Xia
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, United States
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, United States.
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KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABAB Receptor-Induced K+ Currents. J Neurosci 2016; 37:1162-1175. [PMID: 28003345 DOI: 10.1523/jneurosci.2181-16.2016] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 11/29/2016] [Accepted: 12/12/2016] [Indexed: 11/21/2022] Open
Abstract
GABAB receptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, GABA. GABAB receptors were shown to associate with homo-oligomers of auxiliary KCTD8, KCTD12, KCTD12b, and KCTD16 subunits (named after their T1 K+-channel tetramerization domain) that regulate G-protein signaling of the receptor. Here we provide evidence that GABAB receptors also associate with hetero-oligomers of KCTD subunits. Coimmunoprecipitation experiments indicate that two-thirds of the KCTD16 proteins in the hippocampus of adult mice associate with KCTD12. We show that the KCTD proteins hetero-oligomerize through self-interacting T1 and H1 homology domains. Bioluminescence resonance energy transfer measurements in live cells reveal that KCTD12/KCTD16 hetero-oligomers associate with both the receptor and the G-protein. Electrophysiological experiments demonstrate that KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties on G-protein-activated Kir3 currents. During prolonged receptor activation (one min) KCTD12/KCTD16 hetero-oligomers produce moderately desensitizing fast deactivating K+ currents, whereas KCTD12 and KCTD16 homo-oligomers produce strongly desensitizing fast deactivating currents and nondesensitizing slowly deactivating currents, respectively. During short activation (2 s) KCTD12/KCTD16 hetero-oligomers produce nondesensitizing slowly deactivating currents. Electrophysiological recordings from hippocampal neurons of KCTD knock-out mice are consistent with these findings and indicate that KCTD12/KCTD16 hetero-oligomers increase the duration of slow IPSCs. In summary, our data demonstrate that simultaneous assembly of distinct KCTDs at the receptor increases the molecular and functional repertoire of native GABAB receptors and modulates physiologically induced K+ current responses in the hippocampus. SIGNIFICANCE STATEMENT The KCTD proteins 8, 12, and 16 are auxiliary subunits of GABAB receptors that differentially regulate G-protein signaling of the receptor. The KCTD proteins are generally assumed to function as homo-oligomers. Here we show that the KCTD proteins also assemble hetero-oligomers in all possible dual combinations. Experiments in live cells demonstrate that KCTD hetero-oligomers form at least tetramers and that these tetramers directly interact with the receptor and the G-protein. KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties to GABAB receptor-induced Kir3 currents in heterologous cells. KCTD12/KCTD16 hetero-oligomers are abundant in the hippocampus, where they prolong the duration of slow IPSCs in pyramidal cells. Our data therefore support that KCTD hetero-oligomers modulate physiologically induced K+ current responses in the brain.
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Xin W, Edwards N, Bonci A. VTA dopamine neuron plasticity - the unusual suspects. Eur J Neurosci 2016; 44:2975-2983. [PMID: 27711998 DOI: 10.1111/ejn.13425] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/26/2016] [Accepted: 10/03/2016] [Indexed: 12/25/2022]
Abstract
Dopamine neurons in the ventral tegmental area (VTA) are involved in a variety of physiological and pathological conditions, ranging from motivated behaviours to substance use disorders. While many studies have shown that these neurons can express plasticity at excitatory and inhibitory synapses, little is known about how inhibitory inputs and glial activity shape the output of DA neurons and therefore, merit greater discussion. In this review, we will attempt to fill in a bit more of the puzzle, with a focus on inhibitory transmission and astrocyte function. We summarize the findings within the VTA as well as observations made in other brain regions that have important implications for plasticity in general and should be considered in the context of DA neuron plasticity.
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Affiliation(s)
- Wendy Xin
- Synaptic Plasticity Section, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Nicholas Edwards
- Synaptic Plasticity Section, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Antonello Bonci
- Synaptic Plasticity Section, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
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Weidenauer A, Bauer M, Sauerzopf U, Bartova L, Praschak-Rieder N, Sitte HH, Kasper S, Willeit M. Making Sense of: Sensitization in Schizophrenia. Int J Neuropsychopharmacol 2016; 20:1-10. [PMID: 27613293 PMCID: PMC5604613 DOI: 10.1093/ijnp/pyw081] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/07/2016] [Indexed: 12/12/2022] Open
Abstract
Sensitization is defined as a process whereby repeated intermittent exposure to a given stimulus results in an enhanced response at subsequent exposures. Next to robust findings of an increased dopamine synthesis capacity in schizophrenia, empirical data and neuroimaging studies support the notion that the mesolimbic dopamine system of patients with schizophrenia is more reactive compared with healthy controls. These studies led to the conceptualization of schizophrenia as a state of endogenous sensitization, as stronger behavioral response and increased dopamine release after amphetamine administration or exposure to stress have been observed in patients with schizophrenia. These findings have also been integrated into the neurodevelopmental model of the disorder, which assumes that vulnerable neuronal circuits undergo progressive changes during puberty and young adulthood that lead to manifest psychosis. Rodent and human studies have made an attempt to identify the exact mechanisms of sensitization of the dopaminergic system and its association with psychosis. Doing so, several epigenetic and molecular alterations associated with dopamine release, neuroplasticity, and cellular energy metabolism have been discovered. Future research aims at targeting these key proteins associated with sensitization in schizophrenia to enhance the knowledge of the pathophysiology of the illness and pave the way for an improved treatment or even prevention of this severe psychiatric disorder.
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Affiliation(s)
- Ana Weidenauer
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Martin Bauer
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Ulrich Sauerzopf
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Lucie Bartova
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Nicole Praschak-Rieder
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Harald H. Sitte
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
| | - Siegfried Kasper
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte).
| | - Matthäus Willeit
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria (Drs Weidenauer, Bauer, Sauerzopf, Bartova, Praschak-Rieder, Kasper, and Willeit); Department of Clinical Pharmacology (Dr Bauer), and Institute of Pharmacology, Medical University of Vienna, Austria (Dr Sitte)
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A Role for the GIRK3 Subunit in Methamphetamine-Induced Attenuation of GABAB Receptor-Activated GIRK Currents in VTA Dopamine Neurons. J Neurosci 2016; 36:3106-14. [PMID: 26985023 DOI: 10.1523/jneurosci.1327-15.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Repeated exposure to psychostimulants induces locomotor sensitization and leads to persistent changes in the circuitry of the mesocorticolimbic dopamine (DA) system. G-protein-gated inwardly rectifying potassium (GIRK; also known as Kir3) channels mediate a slow IPSC and control the excitability of DA neurons. Repeated 5 d exposure to psychostimulants decreases the size of the GABAB receptor (GABABR)-activated GIRK currents (IBaclofen) in ventral tegmental area (VTA) DA neurons of mice, but the mechanism underlying this plasticity is poorly understood. Here, we show that methamphetamine-dependent attenuation of GABABR-GIRK currents in VTA DA neurons required activation of both D1R-like and D2R-like receptors. The methamphetamine-dependent decrease in GABABR-GIRK currents in VTA DA neurons did not depend on a mechanism of dephosphorylation of the GABAB R2 subunit found previously for other neurons in the reward pathway. Rather, the presence of the GIRK3 subunit appeared critical for the methamphetamine-dependent decrease of GABABR-GIRK current in VTA DA neurons. Together, these results highlight different regulatory mechanisms in the learning-evoked changes that occur in the VTA with repeated exposure to psychostimulants. SIGNIFICANCE STATEMENT Exposure to addictive drugs such as psychostimulants produces persistent adaptations in inhibitory circuits within the mesolimbic dopamine system, suggesting that addictive behaviors are encoded by changes in the reward neural circuitry. One form of neuroadaptation that occurs with repeated exposure to psychostimulants is a decrease in slow inhibition, mediated by a GABAB receptor and a potassium channel. Here, we examine the subcellular mechanism that links psychostimulant exposure with changes in slow inhibition and reveal that one type of potassium channel subunit is important for mediating the effect of repeated psychostimulant exposure. Dissecting out the components of drug-dependent plasticity and uncovering novel protein targets in the reward circuit may lead to the development of new therapeutics for treating addiction.
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Abstract
UNLABELLED Melatonin supplementation has been used as a therapeutic agent for several diseases, yet little is known about the underlying mechanisms by which melatonin synchronizes circadian rhythms. G-protein signaling plays a large role in melatonin-induced phase shifts of locomotor behavior and melatonin receptors activate G-protein-coupled inwardly rectifying potassium (GIRK) channels in Xenopus oocytes. The present study tested the hypothesis that melatonin influences circadian phase and electrical activity within the central clock in the suprachiasmatic nucleus (SCN) through GIRK channel activation. Unlike wild-type littermates, GIRK2 knock-out (KO) mice failed to phase advance wheel-running behavior in response to 3 d subcutaneous injections of melatonin in the late day. Moreover, in vitro phase resetting of the SCN circadian clock by melatonin was blocked by coadministration of a GIRK channel antagonist tertiapin-q (TPQ). Loose-patch electrophysiological recordings of SCN neurons revealed a significant reduction in the average action potential rate in response to melatonin. This effect was lost in SCN slices treated with TPQ and SCN slices from GIRK2 KO mice. The melatonin-induced suppression of firing rate corresponded with an increased inward current that was blocked by TPQ. Finally, application of ramelteon, a potent melatonin receptor agonist, significantly decreased firing rate and increased inward current within SCN neurons in a GIRK-dependent manner. These results are the first to show that GIRK channels are necessary for the effects of melatonin and ramelteon within the SCN. This study suggests that GIRK channels may be an alternative therapeutic target for diseases with evidence of circadian disruption, including aberrant melatonin signaling. SIGNIFICANCE STATEMENT Despite the widespread use of melatonin supplementation for the treatment of sleep disruption and other neurological diseases such as epilepsy and depression, no studies have elucidated the molecular mechanisms linking melatonin-induced changes in neuronal activity to its therapeutic effects. Here, we used behavioral and electrophysiological techniques to address this scientific gap. Our results show that melatonin and ramelteon, a potent and clinically relevant melatonin receptor agonist, significantly affect the neurophysiological function of suprachiasmatic nucleus neurons through activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels. Given the importance of GIRK channels for neuronal excitability (with >600 publications on these channels to date), our study should generate broad interest from neuroscientists in fields such as epilepsy, addiction, and cognition.
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Role of GABA(B) receptors in learning and memory and neurological disorders. Neurosci Biobehav Rev 2016; 63:1-28. [PMID: 26814961 DOI: 10.1016/j.neubiorev.2016.01.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/31/2015] [Accepted: 01/21/2016] [Indexed: 01/13/2023]
Abstract
Although it is evident from the literature that altered GABAB receptor function does affect behavior, these results often do not correspond well. These differences could be due to the task protocol, animal strain, ligand concentration, or timing of administration utilized. Because several clinical populations exhibit learning and memory deficits in addition to altered markers of GABA and the GABAB receptor, it is important to determine whether altered GABAB receptor function is capable of contributing to the deficits. The aim of this review is to examine the effect of altered GABAB receptor function on synaptic plasticity as demonstrated by in vitro data, as well as the effects on performance in learning and memory tasks. Finally, data regarding altered GABA and GABAB receptor markers within clinical populations will be reviewed. Together, the data agree that proper functioning of GABAB receptors is crucial for numerous learning and memory tasks and that targeting this system via pharmaceuticals may benefit several clinical populations.
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Gantz SC, Robinson BG, Buck DC, Bunzow JR, Neve RL, Williams JT, Neve KA. Distinct regulation of dopamine D2S and D2L autoreceptor signaling by calcium. eLife 2015; 4. [PMID: 26308580 PMCID: PMC4575989 DOI: 10.7554/elife.09358] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/25/2015] [Indexed: 11/29/2022] Open
Abstract
D2 autoreceptors regulate dopamine release throughout the brain. Two isoforms of the D2 receptor, D2S and D2L, are expressed in midbrain dopamine neurons. Differential roles of these isoforms as autoreceptors are poorly understood. By virally expressing the isoforms in dopamine neurons of D2 receptor knockout mice, this study assessed the calcium-dependence and drug-induced plasticity of D2S and D2L receptor-dependent G protein-coupled inwardly rectifying potassium (GIRK) currents. The results reveal that D2S, but not D2L receptors, exhibited calcium-dependent desensitization similar to that exhibited by endogenous autoreceptors. Two pathways of calcium signaling that regulated D2 autoreceptor-dependent GIRK signaling were identified, which distinctly affected desensitization and the magnitude of D2S and D2L receptor-dependent GIRK currents. Previous in vivo cocaine exposure removed calcium-dependent D2 autoreceptor desensitization in wild type, but not D2S-only mice. Thus, expression of D2S as the exclusive autoreceptor was insufficient for cocaine-induced plasticity, implying a functional role for the co-expression of D2S and D2L autoreceptors. DOI:http://dx.doi.org/10.7554/eLife.09358.001 Dopamine is an important component of the brain's reward system and is commonly referred to as a ‘feel-good’ chemical. It is mainly released from neurons in the brain in response to natural rewards, such as food or sex, and following exposure to, or in anticipation of, certain drugs of abuse (including cocaine). Dopamine-releasing neurons also sense dopamine, and just like someone can change the volume of their voice by hearing themselves speak, dopamine neurons regulate how much dopamine is released based on how much dopamine they sense. This feedback system is known as autoinhibition. These neurons sense dopamine when it binds to, and activates, so-called ‘dopamine D2 receptors’ on their cell surface. But not all D2 receptors are alike. Instead there are two variants called D2S and D2L. Previous studies have shown that D2 receptor signaling in dopamine neurons is altered by the concentration of calcium ions inside these cells. Furthermore, exposure to cocaine and other drugs is known to change how these calcium ions regulate D2 receptor signaling. Now, Gantz et al. have used mice that produce only a single variant of the D2 receptor (either D2S or D2L) in their dopamine neurons to uncover similarities and differences between the two variants. The experiments show that localized increases in calcium ion concentration make D2S less capable of autoinhibition, like D2 receptors in neurons from wild type mice, without affecting autoinhibition by D2L. In further experiments, some of these mice were given cocaine before D2 receptor signaling was assessed. In dopamine neurons from wild type mice, a single exposure to cocaine eliminates the calcium-dependent regulation; thus, cocaine treatment causes a D2L-like response. In contrast, cocaine treatment did not affect the calcium-dependent regulation when only one variant of the D2 receptor was present. This implies that dopamine neurons must have both D2S and D2L receptors before the drug can induce changes in D2 receptor signaling. These findings also challenge the long-held view that the D2S receptor is the predominant form involved in autoinhibition. The next challenge is to determine how cocaine induces an apparent switch from D2S to D2L and the implications of this switch for the development of cocaine addiction. DOI:http://dx.doi.org/10.7554/eLife.09358.002
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Affiliation(s)
- Stephanie C Gantz
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Brooks G Robinson
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - David C Buck
- Research Service, VA Portland Health Care System, United States Department of Veterans Affairs, Portland, United States
| | - James R Bunzow
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Rachael L Neve
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Kim A Neve
- Research Service, VA Portland Health Care System, United States Department of Veterans Affairs, Portland, United States
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GIRK Channels Modulate Opioid-Induced Motor Activity in a Cell Type- and Subunit-Dependent Manner. J Neurosci 2015; 35:7131-42. [PMID: 25948263 DOI: 10.1523/jneurosci.5051-14.2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
G-protein-gated inwardly rectifying K(+) (GIRK/Kir3) channel activation underlies key physiological effects of opioids, including analgesia and dependence. GIRK channel activation has also been implicated in the opioid-induced inhibition of midbrain GABA neurons and consequent disinhibition of dopamine (DA) neurons in the ventral tegmental area (VTA). Drug-induced disinhibition of VTA DA neurons has been linked to reward-related behaviors and underlies opioid-induced motor activation. Here, we demonstrate that mouse VTA GABA neurons express a GIRK channel formed by GIRK1 and GIRK2 subunits. Nevertheless, neither constitutive genetic ablation of Girk1 or Girk2, nor the selective ablation of GIRK channels in GABA neurons, diminished morphine-induced motor activity in mice. Moreover, direct activation of GIRK channels in midbrain GABA neurons did not enhance motor activity. In contrast, genetic manipulations that selectively enhanced or suppressed GIRK channel function in midbrain DA neurons correlated with decreased and increased sensitivity, respectively, to the motor-stimulatory effect of systemic morphine. Collectively, these data support the contention that the unique GIRK channel subtype in VTA DA neurons, the GIRK2/GIRK3 heteromer, regulates the sensitivity of the mouse mesolimbic DA system to drugs with addictive potential.
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Marron Fernandez de Velasco E, Hearing M, Xia Z, Victoria NC, Luján R, Wickman K. Sex differences in GABA(B)R-GIRK signaling in layer 5/6 pyramidal neurons of the mouse prelimbic cortex. Neuropharmacology 2015; 95:353-60. [PMID: 25843643 DOI: 10.1016/j.neuropharm.2015.03.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 03/10/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
The medial prefrontal cortex (mPFC) has been implicated in multiple disorders characterized by clear sex differences, including schizophrenia, attention deficit hyperactivity disorder, post-traumatic stress disorder, depression, and drug addiction. These sex differences likely represent underlying differences in connectivity and/or the balance of neuronal excitability within the mPFC. Recently, we demonstrated that signaling via the metabotropic γ-aminobutyric acid receptor (GABABR) and G protein-gated inwardly-rectifying K(+) (GIRK/Kir3) channels modulates the excitability of the key output neurons of the mPFC, the layer 5/6 pyramidal neurons. Here, we report a sex difference in the GABABR-GIRK signaling pathway in these neurons. Specifically, GABABR-dependent GIRK currents recorded in the prelimbic region of the mPFC were larger in adolescent male mice than in female counterparts. Interestingly, this sex difference was not observed in layer 5/6 pyramidal neurons of the adjacent infralimbic cortex, nor was it seen in young adult mice. The sex difference in GABABR-GIRK signaling is not attributable to different expression levels of signaling pathway components, but rather to a phosphorylation-dependent trafficking mechanism. Thus, sex differences related to some diseases associated with altered mPFC function may be explained in part by sex differences in GIRK-dependent signaling in mPFC pyramidal neurons.
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Affiliation(s)
| | - Matthew Hearing
- Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Zhilian Xia
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Nicole C Victoria
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Rafael Luján
- IDINE, Departmento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla La Mancha, C/Almansa 14, 02006, Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
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Sharpe AL, Varela E, Bettinger L, Beckstead MJ. Methamphetamine self-administration in mice decreases GIRK channel-mediated currents in midbrain dopamine neurons. Int J Neuropsychopharmacol 2015; 18:pyu073. [PMID: 25522412 PMCID: PMC4376542 DOI: 10.1093/ijnp/pyu073] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Methamphetamine is a psychomotor stimulant with abuse liability and a substrate for catecholamine uptake transporters. Acute methamphetamine elevates extracellular dopamine, which in the midbrain can activate D2 autoreceptors to increase a G-protein gated inwardly rectifying potassium (GIRK) conductance that inhibits dopamine neuron firing. These studies examined the neurophysiological consequences of methamphetamine self-administration on GIRK channel-mediated currents in dopaminergic neurons in the substantia nigra and ventral tegmental area. METHODS Male DBA/2J mice were trained to self-administer intravenous methamphetamine. A dose response was conducted as well as extinction and cue-induced reinstatement. In a second study, after at least 2 weeks of stable self-administration of methamphetamine, electrophysiological brain slice recordings were conducted on dopamine neurons from self-administering and control mice. RESULTS In the first experiment, ad libitum-fed, nonfood-trained mice exhibited a significant increase in intake and locomotion following self-administration as the concentration of methamphetamine per infusion was increased (0.0015-0.15mg/kg/infusion). Mice exhibited extinction in responding and cue-induced reinstatement. In the second experiment, dopamine cells in both the substantia nigra and ventral tegmental area from adult mice with a history of methamphetamine self-administration exhibited significantly smaller D2 and GABAB receptor-mediated currents compared with control mice, regardless of whether their daily self-administration sessions had been 1 or 4 hours. Interestingly, the effects of methamphetamine self-administration were not present when intracellular calcium was chelated by including BAPTA in the recording pipette. CONCLUSIONS Our results suggest that methamphetamine self-administration decreases GIRK channel-mediated currents in dopaminergic neurons and that this effect may be calcium dependent.
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Affiliation(s)
- Amanda L Sharpe
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of the Incarnate Word, San Antonio, Texas (Dr Sharpe, L. Bettinger); Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Sharpe, E. Varela, and Dr Beckstead); Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Beckstead)
| | - Erika Varela
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of the Incarnate Word, San Antonio, Texas (Dr Sharpe, L. Bettinger); Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Sharpe, E. Varela, and Dr Beckstead); Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Beckstead)
| | - Lynne Bettinger
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of the Incarnate Word, San Antonio, Texas (Dr Sharpe, L. Bettinger); Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Sharpe, E. Varela, and Dr Beckstead); Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Beckstead)
| | - Michael J Beckstead
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of the Incarnate Word, San Antonio, Texas (Dr Sharpe, L. Bettinger); Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Sharpe, E. Varela, and Dr Beckstead); Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas (Dr Beckstead).
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de Velasco EMF, McCall N, Wickman K. GIRK Channel Plasticity and Implications for Drug Addiction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:201-38. [DOI: 10.1016/bs.irn.2015.05.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Luján R, Aguado C. Localization and Targeting of GIRK Channels in Mammalian Central Neurons. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:161-200. [PMID: 26422985 DOI: 10.1016/bs.irn.2015.05.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
G protein-gated inwardly rectifying K(+) (GIRK/K(ir)3) channels are critical to brain function. They hyperpolarize neurons in response to activation of different G protein-coupled receptors, reducing cell excitability. Molecular cloning has revealed four distinct mammalian genes (GIRK1-4), which, with the exception of GIRK4, are broadly expressed in the central nervous system (CNS) and have been implicated in a variety of neurological disorders. Although the molecular structure and composition of GIRK channels are key determinants of their biophysical properties, their cellular and subcellular localization patterns and densities on the neuronal surface are just as important to nerve function. Current data obtained with high-resolution quantitative localization techniques reveal complex, subcellular compartment-specific distribution patterns of GIRK channel subunits. Recent efforts have focused on determining the associated proteins that form macromolecular complexes with GIRK channels. Demonstration of the precise subcellular compartmentalization of GIRK channels and their associated proteins represents a crucial step in understanding the contribution of these channels to specific aspects of neuronal function under both physiological and pathological conditions. Here, we present an overview of studies aimed at determining the cellular and subcellular localization of GIRK channel subunits in mammalian brain neurons and discuss implications for neuronal physiology.
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Affiliation(s)
- Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain.
| | - Carolina Aguado
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
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GIRK Channels: A Potential Link Between Learning and Addiction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:239-77. [PMID: 26422987 DOI: 10.1016/bs.irn.2015.05.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ability of drug-associated cues to reinitiate drug craving and seeking, even after long periods of abstinence, has led to the hypothesis that addiction represents a form of pathological learning, in which drugs of abuse hijack normal learning and memory processes to support long-term addictive behaviors. In this chapter, we review evidence suggesting that G protein-gated inwardly rectifying potassium (GIRK/Kir3) channels are one mechanism through which numerous drugs of abuse can modulate learning and memory processes. We will examine the role of GIRK channels in two forms of experience-dependent long-term changes in neuronal function: homeostatic plasticity and synaptic plasticity. We will also discuss how drug-induced changes in GIRK-mediated signaling can lead to changes that support the development and maintenance of addiction.
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37
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Hablitz LM, Molzof HE, Paul JR, Johnson RL, Gamble KL. Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels. J Physiol 2014; 592:5079-92. [PMID: 25217379 DOI: 10.1113/jphysiol.2014.282079] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light-dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2(Luc+/-) background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated.
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Affiliation(s)
- L M Hablitz
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - H E Molzof
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - J R Paul
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - R L Johnson
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - K L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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38
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Sorting nexin 27 regulation of G protein-gated inwardly rectifying K⁺ channels attenuates in vivo cocaine response. Neuron 2014; 82:659-69. [PMID: 24811384 DOI: 10.1016/j.neuron.2014.03.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2014] [Indexed: 12/12/2022]
Abstract
The subcellular pathways that regulate G protein-gated inwardly rectifying potassium (GIRK or Kir3) channels are important for controlling the excitability of neurons. Sorting nexin 27 (SNX27) is a PDZ-containing protein known to bind GIRK2c/GIRK3 channels, but its function in vivo is poorly understood. Here, we investigated the role of SNX27 in regulating GIRK currents in dopamine (DA) neurons of the ventral tegmental area (VTA). Mice lacking SNX27 in DA neurons exhibited reduced GABABR-activated GIRK currents but had normal Ih currents and DA D2R-activated GIRK currents. Expression of GIRK2a, an SNX27-insensitive splice variant, restored GABABR-activated GIRK currents in SNX27-deficient DA neurons. Remarkably, mice with significantly reduced GABABR-activated GIRK currents in only DA neurons were hypersensitive to cocaine and could be restored to a normal locomotor response with GIRK2a expression. These results identify a pathway for regulating excitability of VTA DA neurons, highlighting SNX27 as a promising target for treating addiction.
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Luján R, Marron Fernandez de Velasco E, Aguado C, Wickman K. New insights into the therapeutic potential of Girk channels. Trends Neurosci 2013; 37:20-9. [PMID: 24268819 DOI: 10.1016/j.tins.2013.10.006] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/24/2013] [Accepted: 10/25/2013] [Indexed: 01/01/2023]
Abstract
G protein-dependent signaling pathways control the activity of excitable cells of the nervous system and heart, and are the targets of neurotransmitters, clinically relevant drugs, and drugs of abuse. G protein-gated inwardly rectifying potassium (K(+)) (Girk/Kir3) channels are a key effector in inhibitory signaling pathways. Girk-dependent signaling contributes to nociception and analgesia, reward-related behavior, mood, cognition, and heart-rate regulation, and has been linked to epilepsy, Down syndrome, addiction, and arrhythmias. We discuss recent advances in our understanding of Girk channel structure, organization in signaling complexes, and plasticity, as well as progress on the development of subunit-selective Girk modulators. These findings offer new hope for the selective manipulation of Girk channels to treat a variety of debilitating afflictions.
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Affiliation(s)
- Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain.
| | | | - Carolina Aguado
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, 321 Church Street South East, Minneapolis, MN 55455, USA.
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40
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Molecular mechanism underlying ethanol activation of G-protein-gated inwardly rectifying potassium channels. Proc Natl Acad Sci U S A 2013; 110:18309-14. [PMID: 24145411 DOI: 10.1073/pnas.1311406110] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Alcohol (ethanol) produces a wide range of pharmacological effects on the nervous system through its actions on ion channels. The molecular mechanism underlying ethanol modulation of ion channels is poorly understood. Here we used a unique method of alcohol-tagging to demonstrate that alcohol activation of a G-protein-gated inwardly rectifying potassium (GIRK or Kir3) channel is mediated by a defined alcohol pocket through changes in affinity for the membrane phospholipid signaling molecule phosphatidylinositol 4,5-bisphosphate. Surprisingly, hydrophobicity and size, but not the canonical hydroxyl, were important determinants of alcohol-dependent activation. Altering levels of G protein Gβγ subunits, conversely, did not affect alcohol-dependent activation, suggesting a fundamental distinction between receptor and alcohol gating of GIRK channels. The chemical properties of the alcohol pocket revealed here might extend to other alcohol-sensitive proteins, revealing a unique protein microdomain for targeting alcohol-selective therapeutics in the treatment of alcoholism and addiction.
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41
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Hearing M, Kotecki L, Marron Fernandez de Velasco E, Fajardo-Serrano A, Chung HJ, Luján R, Wickman K. Repeated cocaine weakens GABA(B)-Girk signaling in layer 5/6 pyramidal neurons in the prelimbic cortex. Neuron 2013; 80:159-70. [PMID: 24094109 DOI: 10.1016/j.neuron.2013.07.019] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2013] [Indexed: 01/18/2023]
Abstract
Repeated cocaine exposure triggers adaptations in layer 5/6 glutamatergic neurons in the medial prefrontal cortex (mPFC) that promote behavioral sensitization and drug-seeking behavior. While suppression of metabotropic inhibitory signaling has been implicated in these behaviors, underlying mechanisms are unknown. Here, we show that Girk/K(IR)3 channels mediate most of the GABA(B) receptor (GABA(B)R)-dependent inhibition of layer 5/6 pyramidal neurons in the mPFC and that repeated cocaine suppresses this pathway. This adaptation was selective for GABA(B)R-dependent Girk signaling in layer 5/6 pyramidal neurons of the prelimbic cortex (PrLC) and involved a D₁/₅ dopamine receptor- and phosphorylation-dependent internalization of GABA(B)R and Girk channels. Persistent suppression of Girk signaling in layer 5/6 of the dorsal mPFC enhanced cocaine-induced locomotor activity and occluded behavioral sensitization. Thus, the cocaine-induced suppression of GABA(B)R-Girk signaling in layer 5/6 pyramidal neurons of the prelimbic cortex appears to represent an early adaptation critical for promoting addiction-related behavior.
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Affiliation(s)
- Matthew Hearing
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
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42
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Sugaya N, Kobayashi T, Ikeda K. Role of GIRK Channels in Addictive Substance Effects. ACTA ACUST UNITED AC 2013. [DOI: 10.4303/jdar/235823] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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43
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Wydeven N, Young D, Mirkovic K, Wickman K. Structural elements in the Girk1 subunit that potentiate G protein-gated potassium channel activity. Proc Natl Acad Sci U S A 2012; 109:21492-7. [PMID: 23236146 PMCID: PMC3535602 DOI: 10.1073/pnas.1212019110] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
G protein-gated inwardly rectifying K(+) (Girk/K(IR)3) channels mediate the inhibitory effect of many neurotransmitters on excitable cells. Girk channels are tetramers consisting of various combinations of four mammalian Girk subunits (Girk1 to -4). Although Girk1 is unable to form functional homomeric channels, its presence in cardiac and neuronal channel complexes correlates with robust channel activity. This study sought to better understand the potentiating influence of Girk1, using the GABA(B) receptor and Girk1/Girk2 heteromer as a model system. Girk1 did not increase the protein levels or alter the trafficking of Girk2-containing channels to the cell surface in transfected cells or hippocampal neurons, indicating that its potentiating influence involves enhancement of channel activity. Structural elements in both the distal carboxyl-terminal domain and channel core were identified as key determinants of robust channel activity. In the distal carboxyl-terminal domain, residue Q404 was identified as a key determinant of receptor-induced channel activity. In the Girk1 core, three unique residues in the pore (P) loop (F137, A142, Y150) were identified as a collective potentiating influence on both receptor-dependent and receptor-independent channel activity, exerting their influence, at least in part, by enhancing mean open time and single-channel conductance. Interestingly, the potentiating influence of the Girk1 P-loop is tempered by residue F162 in the second membrane-spanning domain. Thus, discontinuous and sometime opposing elements in Girk1 underlie the Girk1-dependent potentiation of receptor-dependent and receptor-independent heteromeric channel activity.
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Affiliation(s)
- Nicole Wydeven
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455
| | - Daniele Young
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455
| | - Kelsey Mirkovic
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455
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Nimitvilai S, Arora DS, McElvain MA, Brodie MS. Reversal of inhibition of putative dopaminergic neurons of the ventral tegmental area: interaction of GABA(B) and D2 receptors. Neuroscience 2012; 226:29-39. [PMID: 22986166 PMCID: PMC3490029 DOI: 10.1016/j.neuroscience.2012.08.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/21/2012] [Accepted: 08/23/2012] [Indexed: 10/27/2022]
Abstract
Neurons of the ventral tegmental area (VTA) are critical in the rewarding and reinforcing properties of drugs of abuse. Desensitization of VTA neurons to moderate extracellular concentrations of dopamine (DA) is dependent on protein kinase C (PKC) and intracellular calcium levels. This desensitization is called DA inhibition reversal, as it requires concurrent activation of D2 and D1-like receptors; activation of D2 receptors alone does not result in desensitization. Activation of other G-protein-linked receptors can substitute for D1 activation. Like D2 receptors, GABA(B) receptors in the VTA are coupled to G-protein-linked potassium channels. In the present study, we examined interactions between a GABA(B) agonist, baclofen, and dopamine agonists, dopamine and quinpirole, to determine whether there was some interaction in the processes of desensitization of GABA(B) and D2 responses. Long-duration administration of baclofen alone produced reversal of the baclofen-induced inhibition indicative of desensitization, and this desensitization persisted for at least 60 min after baclofen washout. Desensitization to baclofen was dependent on PKC. Dopamine inhibition was reduced for 30 min after baclofen-induced desensitization and conversely, the magnitude of baclofen inhibition was reduced for 30 min by long-duration application of dopamine, but not quinpirole. These results indicate that D2 and GABA(B) receptors share some PKC-dependent mechanisms of receptor desensitization.
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Affiliation(s)
- S Nimitvilai
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 S. Wolcott, Room E-202, M/C 901, Chicago, IL 60612-7342, USA
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45
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Hearing MC, Zink AN, Wickman K. Cocaine-induced adaptations in metabotropic inhibitory signaling in the mesocorticolimbic system. Rev Neurosci 2012; 23:325-51. [PMID: 22944653 DOI: 10.1515/revneuro-2012-0045] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 06/11/2012] [Indexed: 12/17/2022]
Abstract
The addictive properties of psychostimulants such as cocaine are rooted in their ability to activate the mesocorticolimbic dopamine (DA) system. This system consists primarily of dopaminergic projections arising from the ventral tegmental area (VTA) and projecting to the limbic and cortical brain regions, such as the nucleus accumbens (NAc) and prefrontal cortex (PFC). While the basic anatomy and functional relevance of the mesocorticolimbic DA system is relatively well-established, a key challenge remaining in addiction research is to understand where and how molecular adaptations and corresponding changes in function of this system facilitate a pathological desire to seek and take drugs. Several lines of evidence indicate that inhibitory signaling, particularly signaling mediated by the Gi/o class of heterotrimeric GTP-binding proteins (G proteins), plays a key role in the acute and persistent effects of drugs of abuse. Moreover, recent evidence argues that these signaling pathways are targets of drug-induced adaptations. In this review we discuss inhibitory signaling pathways involving DA and the inhibitory neurotransmitter GABA in two brain regions - the VTA and PFC - that are central to the effects of acute and repeated cocaine exposure and represent sites of adaptations linked to addiction-related behaviors including sensitization, craving, and relapse.
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Affiliation(s)
- Matthew C Hearing
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
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46
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Gassmann M, Bettler B. Regulation of neuronal GABA(B) receptor functions by subunit composition. Nat Rev Neurosci 2012; 13:380-94. [PMID: 22595784 DOI: 10.1038/nrn3249] [Citation(s) in RCA: 246] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
GABA(B) receptors (GABA(B)Rs) are G protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the CNS. In the past 5 years, notable advances have been made in our understanding of the molecular composition of these receptors. GABA(B)Rs are now known to comprise principal and auxiliary subunits that influence receptor properties in distinct ways. The principal subunits regulate the surface expression and the axonal versus dendritic distribution of these receptors, whereas the auxiliary subunits determine agonist potency and the kinetics of the receptor response. This Review summarizes current knowledge on how the subunit composition of GABA(B)Rs affects the distribution of these receptors, neuronal processes and higher brain functions.
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Affiliation(s)
- Martin Gassmann
- Department of Biomedicine, Institute of Physiology, University of Basel, Klingelbergstr. 50-70, 4056 Basel, Switzerland.
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47
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Padgett CL, Lalive AL, Tan KR, Terunuma M, Munoz MB, Pangalos MN, Martínez-Hernández J, Watanabe M, Moss SJ, Luján R, Lüscher C, Slesinger PA. Methamphetamine-evoked depression of GABA(B) receptor signaling in GABA neurons of the VTA. Neuron 2012; 73:978-89. [PMID: 22405207 DOI: 10.1016/j.neuron.2011.12.031] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2011] [Indexed: 01/06/2023]
Abstract
Psychostimulants induce neuroadaptations in excitatory and fast inhibitory transmission in the ventral tegmental area (VTA). Mechanisms underlying drug-evoked synaptic plasticity of slow inhibitory transmission mediated by GABA(B) receptors and G protein-gated inwardly rectifying potassium (GIRK/Kir(3)) channels, however, are poorly understood. Here, we show that 1 day after methamphetamine (METH) or cocaine exposure both synaptically evoked and baclofen-activated GABA(B)R-GIRK currents were significantly depressed in VTA GABA neurons and remained depressed for 7 days. Presynaptic inhibition mediated by GABA(B)Rs on GABA terminals was also weakened. Quantitative immunoelectron microscopy revealed internalization of GABA(B1) and GIRK2, which occurred coincident with dephosphorylation of serine 783 (S783) in GABA(B2), a site implicated in regulating GABA(B)R surface expression. Inhibition of protein phosphatases recovered GABA(B)R-GIRK currents in VTA GABA neurons of METH-injected mice. This psychostimulant-evoked impairment in GABA(B)R signaling removes an intrinsic brake on GABA neuron spiking, which may augment GABA transmission in the mesocorticolimbic system.
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Affiliation(s)
- Claire L Padgett
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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