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Torres-Ruiz M, Suárez OJ, López V, Marina P, Sanchis A, Liste I, de Alba M, Ramos V. Effects of 700 and 3500 MHz 5G radiofrequency exposure on developing zebrafish embryos. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 915:169475. [PMID: 38199355 DOI: 10.1016/j.scitotenv.2023.169475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 12/12/2023] [Accepted: 12/16/2023] [Indexed: 01/12/2024]
Abstract
Telecommunications industries are rapidly deploying the fifth generation (5G) spectrum and there is public concern about the safety and health impacts of this type of Radio Frequency Radiation (RFR), in part because of the lack of comparable scientific evidence. In this study we have used a validated commercially available setting producing a uniform field to expose zebrafish embryos (ZFe) to unmodulated 700 and 3500 MHz frequencies. We have combined a battery of toxicity, developmental and behavioral assays to further explore potential RFR effects. Our neurobehavioral profiles include a tail coiling assay, a light/dark activity assay, two thigmotaxis anxiety assays (auditory and visual stimuli), and a startle response - habituation assay in response to auditory stimuli. ZFe were exposed for 1 and 4 h during the blastula period of development and endpoints evaluated up to 120 hours post fertilization (hpf). Our results show no effects on mortality, hatching or body length. However, we have demonstrated specific organ morphological effects, and behavioral effects in activity, anxiety-like behavior, and habituation that lasted in larvae exposed during the early embryonic period. A decrease in acetylcholinesterase activity was also observed and could explain some of the observed behavioral alterations. Interestingly, effects were more pronounced in ZFe exposed to the 700 MHz frequency, and especially for the 4 h exposure period. In addition, we have demonstrated that our exposure setup is robust, flexible with regard to frequency and power testing, and highly comparable. Future work will include exposure of ZFe to 5G modulated signals for different time periods to better understand the potential health effects of novel 5G RFR.
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Affiliation(s)
- Monica Torres-Ruiz
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Oscar J Suárez
- Radio Frequency Laboratory, Telecommunications General Secretary and Audiovisual Communication Services Ordenation, Madrid, Spain
| | - Victoria López
- Chronical Diseases Research Functional Unit (UFIEC), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Pablo Marina
- Telemedicine and eHealth Research Unit, Instituto de Salud Carlos III (ISCIII), Avda. Monforte de Lemos, 5, Madrid 28029, Spain
| | - Aránzazu Sanchis
- Non-Ionizing Radiation Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Isabel Liste
- Chronical Diseases Research Functional Unit (UFIEC), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Mercedes de Alba
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Victoria Ramos
- Telemedicine and eHealth Research Unit, Instituto de Salud Carlos III (ISCIII), Avda. Monforte de Lemos, 5, Madrid 28029, Spain.
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Torres-Ruiz M, de Alba González M, Morales M, Martin-Folgar R, González MC, Cañas-Portilla AI, De la Vieja A. Neurotoxicity and endocrine disruption caused by polystyrene nanoparticles in zebrafish embryo. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 874:162406. [PMID: 36841402 DOI: 10.1016/j.scitotenv.2023.162406] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 02/05/2023] [Accepted: 02/18/2023] [Indexed: 06/18/2023]
Abstract
Nanoplastics (NP) are present in aquatic and terrestrial ecosystems. Humans can be exposed to them through contaminated water, food, air, or personal care products. Mechanisms of NP toxicity are largely unknown and the Zebrafish embryo poses an ideal model to investigate them due to its high homology with humans. Our objective in the present study was to combine a battery of behavioral assays with the study of endocrine related gene expression, to further explore potential NP neurotoxic effects on animal behavior. Polystyrene nanoplastics (PSNP) were used to evaluate NP toxicity. Our neurobehavioral profiles include a tail coiling assay, a light/dark activity assay, two thigmotaxis anxiety assays (auditory and visual stimuli), and a startle response - habituation assay in response to auditory stimuli. Results show PSNP accumulated in eyes, neuromasts, brain, and digestive system organs. PSNP inhibited acetylcholinesterase and altered endocrine-related gene expression profiles both in the thyroid and glucocorticoid axes. At the whole organism level, we observed altered behaviors such as increased activity and anxiety at lower doses and lethargy at a higher dose, which could be due to a variety of complex mechanisms ranging from sensory organ and central nervous system effects to others such as hormonal imbalances. In addition, we present a hypothetical adverse outcome pathway related to these effects. In conclusion, this study provides new understanding into NP toxic effects on zebrafish embryo, emphasizing a critical role of endocrine disruption in observed neurotoxic behavioral effects, and improving our understanding of their potential health risks to human populations.
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Affiliation(s)
- Mónica Torres-Ruiz
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain.
| | - Mercedes de Alba González
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Mónica Morales
- Grupo de Biología y Toxicología Ambiental, Departamento de Física Matemática y de Fluidos, Facultad de Ciencias, UNED, Urbanización Monte Rozas, Avda. Esparta s/n, Ctra. de Las Rozas al Escorial Km 5, 28232 Las Rozas, Madrid, Spain
| | - Raquel Martin-Folgar
- Grupo de Biología y Toxicología Ambiental, Departamento de Física Matemática y de Fluidos, Facultad de Ciencias, UNED, Urbanización Monte Rozas, Avda. Esparta s/n, Ctra. de Las Rozas al Escorial Km 5, 28232 Las Rozas, Madrid, Spain
| | - Mª Carmen González
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain
| | - Ana I Cañas-Portilla
- Environmental Toxicology Unit, Centro Nacional de Sanidad Ambiental (CNSA), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain.
| | - Antonio De la Vieja
- Endocrine Tumor Unit, Unidad Funcional de Investigación en Enfermedades Crónicas (UFIEC), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo Km. 2,2., Majadahonda, Madrid 28220, Spain.
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Perez JD, Rubinstein ND, Dulac C. New Perspectives on Genomic Imprinting, an Essential and Multifaceted Mode of Epigenetic Control in the Developing and Adult Brain. Annu Rev Neurosci 2016; 39:347-84. [PMID: 27145912 DOI: 10.1146/annurev-neuro-061010-113708] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mammalian evolution entailed multiple innovations in gene regulation, including the emergence of genomic imprinting, an epigenetic regulation leading to the preferential expression of a gene from its maternal or paternal allele. Genomic imprinting is highly prevalent in the brain, yet, until recently, its central roles in neural processes have not been fully appreciated. Here, we provide a comprehensive survey of adult and developmental brain functions influenced by imprinted genes, from neural development and wiring to synaptic function and plasticity, energy balance, social behaviors, emotions, and cognition. We further review the widespread identification of parental biases alongside monoallelic expression in brain tissues, discuss their potential roles in dosage regulation of key neural pathways, and suggest possible mechanisms underlying the dynamic regulation of imprinting in the brain. This review should help provide a better understanding of the significance of genomic imprinting in the normal and pathological brain of mammals including humans.
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Affiliation(s)
- Julio D Perez
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
| | - Nimrod D Rubinstein
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
| | - Catherine Dulac
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
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Yang A, Daya T, Carlton K, Yan JH, Schmid S. Differential effect of clomipramine on habituation and prepulse inhibition in dominant versus subordinate rats. Eur Neuropsychopharmacol 2016; 26:591-601. [PMID: 26754403 DOI: 10.1016/j.euroneuro.2015.12.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/24/2015] [Accepted: 12/12/2015] [Indexed: 02/06/2023]
Abstract
Many patients with depression have comorbidities associated with an impairment of sensorimotor gating, such as e.g. schizophrenia, Parkinson Disease, or Alzheimer disease. Anti-depressants like clomipramine that modulate serotonergic or norepinephrinergic neurotransmission have been shown to impact sensorimotor gating, it is therefore important to study potential effects of clomipramine in order to rule out an exacerbation of sensorimotor gating impairment. Prior studies in animals and humans have been inconclusive. Since serotonin and norepinephrine levels are closely related to anxiety and stress levels and therefore to the social status of an animal, we tested the hypothesis that acute and chronic effects of clomipramine on sensorimotor gating are different in dominant versus subordinate rats, which might be responsible for conflicting results in past animal studies. We used habituation and prepulse inhibition (PPI) of the acoustic startle response as operational measures of sensorimotor gating. After establishing the dominant animal in pair-housed male rats, we injected clomipramine for two weeks and measured acute effects on baseline startle, habituation and PPI after the first injection and chronic effects at the end of the two weeks. Chronic treatment with clomipramine significantly increased habituation in subordinate rats, but had no effect on habituation in dominant animals. Furthermore, PPI was slightly enhanced in subordinate rats upon chronic treatment while no changes occurred in dominant animals. We conclude that the social status of an animal, and therefore the basic anxiety/stress level determines whether or not clomipramine has a beneficial effect on sensorimotor gating and discuss possible underlying mechanisms.
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Affiliation(s)
- Alvin Yang
- Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Tahira Daya
- Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Karen Carlton
- Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Jin Hui Yan
- Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Susanne Schmid
- Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada.
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TASK Channels on Basal Forebrain Cholinergic Neurons Modulate Electrocortical Signatures of Arousal by Histamine. J Neurosci 2016; 35:13555-67. [PMID: 26446210 DOI: 10.1523/jneurosci.1445-15.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
UNLABELLED Basal forebrain cholinergic neurons are the main source of cortical acetylcholine, and their activation by histamine elicits cortical arousal. TWIK-like acid-sensitive K(+) (TASK) channels modulate neuronal excitability and are expressed on basal forebrain cholinergic neurons, but the role of TASK channels in the histamine-basal forebrain cholinergic arousal circuit is unknown. We first expressed TASK channel subunits and histamine Type 1 receptors in HEK cells. Application of histamine in vitro inhibited the acid-sensitive K(+) current, indicating a functionally coupled signaling mechanism. We then studied the role of TASK channels in modulating electrocortical activity in vivo using freely behaving wild-type (n = 12) and ChAT-Cre:TASK(f/f) mice (n = 12), the latter lacking TASK-1/3 channels on cholinergic neurons. TASK channel deletion on cholinergic neurons significantly altered endogenous electroencephalogram oscillations in multiple frequency bands. We then identified the effect of TASK channel deletion during microperfusion of histamine into the basal forebrain. In non-rapid eye movement sleep, TASK channel deletion on cholinergic neurons significantly attenuated the histamine-induced increase in 30-50 Hz activity, consistent with TASK channels contributing to histamine action on basal forebrain cholinergic neurons. In contrast, during active wakefulness, histamine significantly increased 30-50 Hz activity in ChAT-Cre:TASK(f/f) mice but not wild-type mice, showing that the histamine response depended upon the prevailing cortical arousal state. In summary, we identify TASK channel modulation in response to histamine receptor activation in vitro, as well as a role of TASK channels on cholinergic neurons in modulating endogenous oscillations in the electroencephalogram and the electrocortical response to histamine at the basal forebrain in vivo. SIGNIFICANCE STATEMENT Attentive states and cognitive function are associated with the generation of γ EEG activity. Basal forebrain cholinergic neurons are important modulators of cortical arousal and γ activity, and in this study we investigated the mechanism by which these neurons are activated by the wake-active neurotransmitter histamine. We found that histamine inhibited a class of K(+) leak channels called TASK channels and that deletion of TASK channels selectively on cholinergic neurons modulated baseline EEG activity as well as histamine-induced changes in γ activity. By identifying a discrete brain circuit where TASK channels can influence γ activity, these results represent new knowledge that enhances our understanding of how subcortical arousal systems may contribute to the generation of attentive states.
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Donner NC, Siebler PH, Johnson DT, Villarreal MD, Mani S, Matti AJ, Lowry CA. Serotonergic systems in the balance: CRHR1 and CRHR2 differentially control stress-induced serotonin synthesis. Psychoneuroendocrinology 2016; 63:178-90. [PMID: 26454419 PMCID: PMC4695240 DOI: 10.1016/j.psyneuen.2015.09.024] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 09/21/2015] [Accepted: 09/22/2015] [Indexed: 12/14/2022]
Abstract
Anxiety and affective disorders are often associated with hypercortisolism and dysfunctional serotonergic systems, including increased expression of TPH2, the gene encoding the rate-limiting enzyme of neuronal serotonin synthesis. We previously reported that chronic glucocorticoid exposure is anxiogenic and increases rat Tph2 mRNA expression, but it was still unclear if this also translates to increased TPH2 protein levels and in vivo activity of the enzyme. Here, we found that adult male rats treated with corticosterone (CORT, 100 μg/ml) via the drinking water for 21 days indeed show increased TPH2 protein expression in the dorsal and ventral part of the dorsal raphe nucleus (DRD, DRV) during the light phase, abolishing the enzyme's diurnal rhythm. In a second study, we systemically blocked the conversion of 5-hydroxytryptophan (5-HTP) to serotonin immediately before rats treated with CORT or vehicle were either exposed to 30 min acoustic startle stress or home cage control conditions. This allowed us to measure 5-HTP accumulation as a direct readout of basal versus stress-induced in vivo TPH2 activity. As expected, basal TPH2 activity was elevated in the DRD, DRV and MnR of CORT-treated rats. In response to stress, a multitude of serotonergic systems reacted with increased TPH2 activity, but the stress-, anxiety-, and learned helplessness-related dorsal and caudal DR (DRD/DRC) displayed stress-induced increases in TPH2 activity only after chronic CORT-treatment. To address the mechanisms underlying this region-specific CORT-dependent sensitization, we stereotaxically implanted CORT-treated rats with cannulae targeting the DR, and pharmacologically blocked either corticotropin-releasing hormone receptor type 1 (CRHR1) or type 2 (CRHR2) 10 min prior to acoustic startle stress. CRHR2 blockade prevented stress-induced increases of TPH2 activity within the DRD/DRC, while blockade of CRHR1 potentiated stress-induced TPH2 activity in the entire DR. Stress-induced TPH2 activity in the DRD/DRC furthermore predicted TPH2 activity in the amygdala and in the caudal pontine reticular nucleus (PnC), while serotonin synthesis in the PnC was strongly correlated with the maximum startle response. Our data demonstrate that chronically elevated glucocorticoids sensitize stress- and anxiety-related serotonergic systems, and for the first time reveal competing roles of CRHR1 and CRHR2 on stress-induced in vivo serotonin synthesis.
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Affiliation(s)
- Nina C. Donner
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA,Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Kraepelinstr. 2-10, 80804 Munich, Germany,Corresponding author at: Nina C. Donner, Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Kraepelinstr. 2-10, 80804 Munich, Germany. Tel.: +49 (0)89 30622 554
| | - Philip H. Siebler
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
| | - Danté T. Johnson
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
| | - Marcos D. Villarreal
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
| | - Sofia Mani
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
| | - Allison J. Matti
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
| | - Christopher A. Lowry
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, 1725 Pleasant Street, 114 Clare Small, UCB 354, 80309 Boulder, CO, USA
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Marcinkiewcz CA, Dorrier CE, Lopez AJ, Kash TL. Ethanol induced adaptations in 5-HT2c receptor signaling in the bed nucleus of the stria terminalis: implications for anxiety during ethanol withdrawal. Neuropharmacology 2015; 89:157-67. [PMID: 25229718 PMCID: PMC4469779 DOI: 10.1016/j.neuropharm.2014.09.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 08/18/2014] [Accepted: 09/02/2014] [Indexed: 01/13/2023]
Abstract
One of the hallmarks of alcohol dependence is the presence of a withdrawal syndrome during abstinence, which manifests as physical craving for alcohol accompanied by subjective feelings of anxiety. Using a model of chronic intermittent ethanol (CIE) vapor in mice, we investigated the role of serotonin2c receptor (5HT2c-R) signaling in the BNST as a neural substrate underlying ethanol-induced anxiety during withdrawal. Mice were subjected to a 5-day CIE regimen of 16 h of ethanol vapor exposure followed by an 8 h "withdrawal" period between exposures. After the 5th and final exposure, mice were withdrawn for 24 h or 1 week before experiments began. Anxiety-like behavior was assessed in the social approach, light dark, and open field tests with mice showing deficits in social, but not general anxiety-like behavior that was alleviated by pretreatment with the 5HT2c-R antagonist SB 242,084 (3 mg/kg, i.p.) 24 h and 1 week post-CIE. Using immunohistochemistry and whole cell patch clamp electrophysiology, we also found that CIE increased FOS-IR and enhanced neuronal excitability in the ventral BNST (vBNST) 24 h into withdrawal in a 5HT2c-R dependent manner. This enhanced excitability persisted for 1 week post-CIE. We also found that mCPP, a 5HT2c/b agonist, induced a more robust depolarization in cells of the vBNST in CIE mice, confirming that 5HT2c-R signaling is upregulated in the vBNST following CIE. Taken together, these results suggest that CIE upregulates 5HT2c-R signaling in the vBNST, leading to increased excitability. This enhanced excitability of the vBNST may drive increased anxiety-like behavior during ethanol withdrawal.
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Affiliation(s)
- Catherine A Marcinkiewcz
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Cayce E Dorrier
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alberto J Lopez
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Thomas L Kash
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Braun G, Lengyel M, Enyedi P, Czirják G. Differential sensitivity of TREK-1, TREK-2 and TRAAK background potassium channels to the polycationic dye ruthenium red. Br J Pharmacol 2015; 172:1728-38. [PMID: 25409575 DOI: 10.1111/bph.13019] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 10/15/2014] [Accepted: 11/11/2014] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Pharmacological separation of the background potassium currents of closely related K2P channels is a challenging problem. We previously demonstrated that ruthenium red (RR) inhibits TASK-3 (K2 P 9.1), but not TASK-1 (K2 P 3.1) channels. RR has been extensively used to distinguish between TASK currents in native cells. In the present study, we systematically investigate the RR sensitivity of a more comprehensive set of K2 P channels. EXPERIMENTAL APPROACH K(+) currents were measured by two-electrode voltage clamp in Xenopus oocytes and by whole-cell patch clamp in mouse dorsal root ganglion (DRG) neurons. KEY RESULTS RR differentiates between two closely related members of the TREK subfamily. TREK-2 (K2 P 10.1) proved to be highly sensitive to RR (IC50 = 0.2 μM), whereas TREK-1 (K2 P 2.1) was not affected by the compound. We identified aspartate 135 (D135) as the target of the inhibitor in mouse TREK-2c. D135 lines the wall of the extracellular ion pathway (EIP), a tunnel structure through the extracellular cap characteristic for K2 P channels. TREK-1 contains isoleucine in the corresponding position. The mutation of this isoleucine (I110D) rendered TREK-1 sensitive to RR. The third member of the TREK subfamily, TRAAK (K2 P 4.1) was more potently inhibited by ruthenium violet, a contaminant in some RR preparations, than by RR. DRG neurons predominantly express TREK-2 and RR-resistant TREK-1 and TRESK (K2 P 18.1) background K(+) channels. We detected the RR-sensitive leak K(+) current component in DRG neurons. CONCLUSIONS AND IMPLICATIONS We propose that RR may be useful for distinguishing TREK-2 (K2P 10.1) from TREK-1 (K2P 2.1) and other RR-resistant K2 P channels in native cells.
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Affiliation(s)
- G Braun
- Department of Physiology, Semmelweis University, Budapest, Hungary
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Ehling P, Cerina M, Budde T, Meuth SG, Bittner S. The CNS under pathophysiologic attack--examining the role of K₂p channels. Pflugers Arch 2014; 467:959-72. [PMID: 25482672 DOI: 10.1007/s00424-014-1664-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 11/17/2014] [Accepted: 11/28/2014] [Indexed: 10/24/2022]
Abstract
Members of the two-pore domain K(+) channel (K2P) family are increasingly recognized as being potential targets for therapeutic drugs and could play a role in the diagnosis and treatment of neurologic disorders. Their broad and diverse expression pattern in pleiotropic cell types, importance in cellular function, unique biophysical properties, and sensitivity toward pathophysiologic parameters represent the basis for their involvement in disorders of the central nervous system (CNS). This review will focus on multiple sclerosis (MS) and stroke, as there is growing evidence for the involvement of K2P channels in these two major CNS disorders. In MS, TASK1-3 channels are expressed on T lymphocytes and are part of a signaling network regulating Ca(2+)- dependent pathways that are mandatory for T cell activation, differentiation, and effector functions. In addition, TASK1 channels are involved in neurodegeneration, resulting in autoimmune attack of CNS cells. On the blood-brain barrier, TREK1 channels regulate immune cell trafficking under autoinflammatory conditions. Cerebral ischemia shares some pathophysiologic similarities with MS, including hypoxia and extracellular acidosis. On a cellular level, K2P channels can have both proapoptotic and antiapoptotic effects, either promoting neurodegeneration or protecting neurons from ischemic cell death. TASK1 and TREK1 channels have a neuroprotective effect on stroke development, whereas TASK2 channels have a detrimental effect on neuronal survival under ischemic conditions. Future research in preclinical models is needed to provide a more detailed understanding of the contribution of K2P channel family members to neurologic disorders, before translation to the clinic is an option.
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Affiliation(s)
- Petra Ehling
- Department of Neurology, University of Münster, Münster, Germany,
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Dadi PK, Vierra NC, Jacobson DA. Pancreatic β-cell-specific ablation of TASK-1 channels augments glucose-stimulated calcium entry and insulin secretion, improving glucose tolerance. Endocrinology 2014; 155:3757-68. [PMID: 24932805 PMCID: PMC4164933 DOI: 10.1210/en.2013-2051] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calcium entry through voltage-dependent Ca(2+) channels (VDCCs) is required for pancreatic β-cell insulin secretion. The 2-pore-domain acid-sensitive potassium channel (TASK-1) regulates neuronal excitability and VDCC activation by hyperpolarizing the plasma membrane potential (Δψp); however, a role for pancreatic β-cell TASK-1 channels is unknown. Here we examined the influence of TASK-1 channel activity on the β-cell Δψp and insulin secretion during secretagogue stimulation. TASK-1 channels were found to be highly expressed in human and rodent islets and localized to the plasma membrane of β-cells. TASK-1-like currents of mouse and human β-cells were blocked by the potent TASK-1 channel inhibitor, A1899 (250nM). Although inhibition of TASK-1 currents did not influence the β-cell Δψp in the presence of low (2mM) glucose, A1899 significantly enhanced glucose-stimulated (14mM) Δψp depolarization of human and mouse β-cells. TASK-1 inhibition also resulted in greater secretagogue-stimulated Ca(2+) influx in both human and mouse islets. Moreover, conditional ablation of mouse β-cell TASK-1 channels reduced K2P currents, increased glucose-stimulated Δψp depolarization, and augmented secretagogue-stimulated Ca(2+) influx. The Δψp depolarization caused by TASK-1 inhibition resulted in a transient increase in glucose-stimulated mouse β-cell action potential (AP) firing frequency. However, secretagogue-stimulated β-cell AP duration eventually increased in the presence of A1899 as well as in β-cells without TASK-1, causing a decrease in AP firing frequency. Ablation or inhibition of mouse β-cell TASK-1 channels also significantly enhanced glucose-stimulated insulin secretion, which improved glucose tolerance. Conversely, TASK-1 ablation did not perturb β-cell Δψp, Ca(2+) influx, or insulin secretion under low-glucose conditions (2mM). These results reveal a glucose-dependent role for β-cell TASK-1 channels of limiting glucose-stimulated Δψp depolarization and insulin secretion, which modulates glucose homeostasis.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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Paul ED, Johnson PL, Shekhar A, Lowry CA. The Deakin/Graeff hypothesis: focus on serotonergic inhibition of panic. Neurosci Biobehav Rev 2014; 46 Pt 3:379-96. [PMID: 24661986 PMCID: PMC4170046 DOI: 10.1016/j.neubiorev.2014.03.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 02/15/2014] [Accepted: 03/01/2014] [Indexed: 12/20/2022]
Abstract
The Deakin/Graeff hypothesis proposes that different subpopulations of serotonergic neurons through topographically organized projections to forebrain and brainstem structures modulate the response to acute and chronic stressors, and that dysfunction of these neurons increases vulnerability to affective and anxiety disorders, including panic disorder. We outline evidence supporting the existence of a serotonergic system originally discussed by Deakin/Graeff that is implicated in the inhibition of panic-like behavioral and physiological responses. Evidence supporting this panic inhibition system comes from the following observations: (1) serotonergic neurons located in the 'ventrolateral dorsal raphe nucleus' (DRVL) as well as the ventrolateral periaqueductal gray (VLPAG) inhibit dorsal periaqueductal gray-elicited panic-like responses; (2) chronic, but not acute, antidepressant treatment potentiates serotonin's panicolytic effect; (3) contextual fear activates a central nucleus of the amygdala-DRVL/VLPAG circuit implicated in mediating freezing and inhibiting panic-like escape behaviors; (4) DRVL/VLPAG serotonergic neurons are central chemoreceptors and modulate the behavioral and cardiorespiratory response to panicogenic agents such as sodium lactate and CO2. Implications of the panic inhibition system are discussed.
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Affiliation(s)
- Evan D Paul
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Philip L Johnson
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Anantha Shekhar
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Christopher A Lowry
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
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12
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Nucleus accumbens shell excitability is decreased by methamphetamine self-administration and increased by 5-HT2C receptor inverse agonism and agonism. Neuropharmacology 2014; 89:113-21. [PMID: 25229719 DOI: 10.1016/j.neuropharm.2014.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 07/25/2014] [Accepted: 09/01/2014] [Indexed: 11/21/2022]
Abstract
Methamphetamine profoundly increases brain monoamines and is a widely abused psychostimulant. The effects of methamphetamine self-administration on neuron function are not known for the nucleus accumbens, a brain region involved in addictive behaviors, including drug-seeking. One therapeutic target showing preclinical promise at attenuating psychostimulant-seeking is 5-HT2C receptors; however, the effects of 5-HT2C receptor ligands on neuronal physiology are unclear. 5-HT2C receptor agonism decreases psychostimulant-mediated behaviors, and the putative 5-HT2C receptor inverse agonist, SB 206553, attenuates methamphetamine-seeking in rats. To ascertain the effects of methamphetamine, and 5-HT2C receptor inverse agonism and agonism, on neuronal function in the nucleus accumbens, we evaluated methamphetamine, SB 206553, and the 5-HT2C receptor agonist and Ro 60-0175, on neuronal excitability within the accumbens shell subregion using whole-cell current-clamp recordings in forebrain slices ex vivo. We reveal that methamphetamine self-administration decreased generation of evoked action potentials. In contrast, SB 206553 and Ro 60-0175 increased evoked spiking, effects that were prevented by the 5-HT2C receptor antagonist, SB 242084. We also assessed signaling mechanisms engaged by 5-HT2C receptors, and determined that accumbal 5-HT2C receptors stimulated Gq, but not Gi/o. These findings demonstrate that methamphetamine-induced decreases in excitability of neurons within the nucleus accumbens shell were abrogated by both 5-HT2C inverse agonism and agonism, and this effect likely involved activation of Gq-mediated signaling pathways.
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13
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Jalewa J, Joshi A, McGinnity TM, Prasad G, Wong-Lin K, Hölscher C. Neural circuit interactions between the dorsal raphe nucleus and the lateral hypothalamus: an experimental and computational study. PLoS One 2014; 9:e88003. [PMID: 24516577 PMCID: PMC3916338 DOI: 10.1371/journal.pone.0088003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 01/02/2014] [Indexed: 12/22/2022] Open
Abstract
Orexinergic/hypocretinergic (Ox) neurotransmission plays an important role in regulating sleep, as well as in anxiety and depression, for which the serotonergic (5-HT) system is also involved in. However, little is known regarding the direct and indirect interactions between 5-HT in the dorsal raphe nucleus (DRN) and Ox neurons in the lateral hypothalamus (LHA). In this study, we report the additional presence of 5-HT1BR, 5-HT2AR, 5-HT2CR and fast ligand-gated 5-HT3AR subtypes on the Ox neurons of transgenic Ox-enhanced green fluorescent protein (Ox-EGFP) and wild type C57Bl/6 mice using single and double immunofluorescence (IF) staining, respectively, and quantify the colocalization for each 5-HT receptor subtype. We further reveal the presence of 5-HT3AR and 5-HT1AR on GABAergic neurons in LHA. We also identify NMDAR1, OX1R and OX2R on Ox neurons, but none on adjacent GABAergic neurons. This suggests a one-way relationship between LHA's GABAergic and Ox neurons, wherein GABAergic neurons exerts an inhibitory effect on Ox neurons under partial DRN's 5-HT control. We also show that Ox axonal projections receive glutamatergic (PSD-95 immunopositive) and GABAergic (Gephyrin immunopositive) inputs in the DRN. We consider these and other available findings into our computational model to explore possible effects of neural circuit connection types and timescales on the DRN-LHA system's dynamics. We find that if the connections from 5-HT to LHA's GABAergic neurons are weakly excitatory or inhibitory, the network exhibits slow oscillations; not observed when the connection is strongly excitatory. Furthermore, if Ox directly excites 5-HT neurons at a fast timescale, phasic Ox activation can lead to an increase in 5-HT activity; no significant effect with slower timescale. Overall, our experimental and computational approaches provide insights towards a more complete understanding of the complex relationship between 5-HT in the DRN and Ox in the LHA.
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Affiliation(s)
- Jaishree Jalewa
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, United Kingdom
| | - Alok Joshi
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Londonderry, Northern Ireland, United Kingdom
| | - T. Martin McGinnity
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Londonderry, Northern Ireland, United Kingdom
| | - Girijesh Prasad
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Londonderry, Northern Ireland, United Kingdom
| | - KongFatt Wong-Lin
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Londonderry, Northern Ireland, United Kingdom
- * E-mail: (CH); (KW)
| | - Christian Hölscher
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster, United Kingdom
- * E-mail: (CH); (KW)
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14
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Asan E, Steinke M, Lesch KP. Serotonergic innervation of the amygdala: targets, receptors, and implications for stress and anxiety. Histochem Cell Biol 2013; 139:785-813. [DOI: 10.1007/s00418-013-1081-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2013] [Indexed: 01/09/2023]
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15
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Serotonergic innervation and serotonin receptor expression of NPY-producing neurons in the rat lateral and basolateral amygdaloid nuclei. Brain Struct Funct 2012; 218:421-35. [PMID: 22527118 PMCID: PMC3580143 DOI: 10.1007/s00429-012-0406-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Accepted: 03/13/2012] [Indexed: 01/28/2023]
Abstract
Pharmacobehavioral studies in experimental animals, and imaging studies in humans, indicate that serotonergic transmission in the amygdala plays a key role in emotional processing, especially for anxiety-related stimuli. The lateral and basolateral amygdaloid nuclei receive a dense serotonergic innervation in all species studied to date. We investigated interrelations between serotonergic afferents and neuropeptide Y (NPY)-producing neurons, which are a subpopulation of inhibitory interneurons in the rat lateral and basolateral nuclei with particularly strong anxiolytic properties. Dual light microscopic immunolabeling showed numerous appositions of serotonergic afferents on NPY-immunoreactive somata. Using electron microscopy, direct membrane appositions and synaptic contacts between serotonin-containing axon terminals and NPY-immunoreactive cellular profiles were unequivocally established. Double in situ hybridization documented that more than 50 %, and about 30–40 % of NPY mRNA-producing neurons, co-expressed inhibitory 5-HT1A and excitatory 5-HT2C mRNA receptor subtype mRNA, respectively, in both nuclei with no gender differences. Triple in situ hybridization showed that individual NPY mRNA-producing interneurons co-express both 5-HT1A and 5-HT2C mRNAs. Co-expression of NPY and 5-HT3 mRNA was not observed. The results demonstrate that serotonergic afferents provide substantial innervation of NPY-producing neurons in the rat lateral and basolateral amygdaloid nuclei. Studies of serotonin receptor subtype co-expression indicate a differential impact of the serotonergic innervation on this small, but important, population of anxiolytic interneurons, and provide the basis for future studies of the circuitry underlying serotonergic modulation of emotional stimulus processing in the amygdala.
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Bonn M, Schmitt A, Asan E. Double and triple in situ hybridization for coexpression studies: combined fluorescent and chromogenic detection of neuropeptide Y (NPY) and serotonin receptor subtype mRNAs expressed at different abundance levels. Histochem Cell Biol 2012; 137:11-24. [PMID: 22075564 PMCID: PMC3249186 DOI: 10.1007/s00418-011-0882-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2011] [Indexed: 12/17/2022]
Abstract
Multiple fluorescence in situ hybridization is the method of choice for studies aimed at determining simultaneous production of signal transduction molecules and neuromodulators in neurons. In our analyses of the monoamine receptor mRNA expression of peptidergic neurons in the rat telencephalon, double tyramide-signal-amplified fluorescence in situ hybridization delivered satisfactory results for coexpression analysis of neuropeptide Y (NPY) and serotonin receptor 2C (5-HT2C) mRNA, a receptor subtype expressed at high-to-moderate abundance in the regions analyzed. However, expression of 5-HT1A mRNA, which is expressed at comparatively low abundance in many telencephalic areas, could not be unequivocally identified in NPY mRNA-reactive neurons due to high background and poor signal-to-noise ratio in fluorescent receptor mRNA detections. Parallel chromogenic in situ hybridization provided clear labeling for 5-HT1A mRNA and additionally offered the possibility to monitor the chromogen deposition at regular time intervals to determine the optimal signal-to-noise ratio. We first developed a double labeling protocol combining fluorescence and chromogenic in situ hybridization and subsequently expanded this variation to combine double fluorescence and chromogenic in situ hybridization for triple labelings. With this method, we documented expression of 5-HT2C and/or 5-HT1A in subpopulations of telencephalic NPY-producing neurons. The method developed in the present study appears suitable for conventional light and fluorescence microscopy, combines advantages of fluorescence and chromogenic in situ hybridization protocols and thus provides a reliable non-radioactive alternative to previously published multiple labeling methods for coexpression analyses in which one mRNA species requires highly sensitive detection.
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Affiliation(s)
- Maria Bonn
- Institute of Anatomy and Cell Biology, University of Wuerzburg, Koellikerstr. 6, 97070 Wuerzburg, Germany
| | - Angelika Schmitt
- Department of Psychiatry, Psychosomatics and Psychotherapy, University of Wuerzburg, Fuechsleinstr. 15, 97080 Wuerzburg, Germany
| | - Esther Asan
- Institute of Anatomy and Cell Biology, University of Wuerzburg, Koellikerstr. 6, 97070 Wuerzburg, Germany
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17
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Zhao S, Golowasch J, Nadim F. Pacemaker neuron and network oscillations depend on a neuromodulator-regulated linear current. Front Behav Neurosci 2010; 4:21. [PMID: 20514340 PMCID: PMC2876874 DOI: 10.3389/fnbeh.2010.00021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 04/16/2010] [Indexed: 11/17/2022] Open
Abstract
Linear leak currents have been implicated in the regulation of neuronal excitability, generation of neuronal and network oscillations, and network state transitions. Yet, few studies have directly tested the dependence of network oscillations on leak currents or explored the role of leak currents on network activity. In the oscillatory pyloric network of decapod crustaceans neuromodulatory inputs are necessary for pacemaker activity. A large subset of neuromodulators is known to activate a single voltage-gated inward current IMI, which has been shown to regulate the rhythmic activity of the network and its pacemaker neurons. Using the dynamic clamp technique, we show that the crucial component of IMI for the generation of oscillatory activity is only a close-to-linear portion of the current-voltage relationship. The nature of this conductance is such that the presence or the absence of neuromodulators effectively regulates the amount of leak current and the input resistance in the pacemaker neurons. When deprived of neuromodulatory inputs, pyloric oscillations are disrupted; yet, a linear reduction of the total conductance in a single neuron within the pacemaker group recovers not only the pacemaker activity in that neuron, but also leads to a recovery of oscillations in the entire pyloric network. The recovered activity produces proper frequency and phasing that is similar to that induced by neuromodulators. These results show that the passive properties of pacemaker neurons can significantly affect their capacity to generate and regulate the oscillatory activity of an entire network, and that this feature is exploited by neuromodulatory inputs.
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Affiliation(s)
- Shunbing Zhao
- Federated Department of Biological Sciences, Rutgers University and New Jersey Institute of Technology Newark, NJ, USA
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18
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Enyedi P, Czirják G. Molecular background of leak K+ currents: two-pore domain potassium channels. Physiol Rev 2010; 90:559-605. [PMID: 20393194 DOI: 10.1152/physrev.00029.2009] [Citation(s) in RCA: 620] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Two-pore domain K(+) (K(2P)) channels give rise to leak (also called background) K(+) currents. The well-known role of background K(+) currents is to stabilize the negative resting membrane potential and counterbalance depolarization. However, it has become apparent in the past decade (during the detailed examination of the cloned and corresponding native K(2P) channel types) that this primary hyperpolarizing action is not performed passively. The K(2P) channels are regulated by a wide variety of voltage-independent factors. Basic physicochemical parameters (e.g., pH, temperature, membrane stretch) and also several intracellular signaling pathways substantially and specifically modulate the different members of the six K(2P) channel subfamilies (TWIK, TREK, TASK, TALK, THIK, and TRESK). The deep implication in diverse physiological processes, the circumscribed expression pattern of the different channels, and the interesting pharmacological profile brought the K(2P) channel family into the spotlight. In this review, we focus on the physiological roles of K(2P) channels in the most extensively investigated cell types, with special emphasis on the molecular mechanisms of channel regulation.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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Segal-Hayoun Y, Cohen A, Zilberberg N. Molecular mechanisms underlying membrane-potential-mediated regulation of neuronal K2P2.1 channels. Mol Cell Neurosci 2009; 43:117-26. [PMID: 19837167 DOI: 10.1016/j.mcn.2009.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2009] [Revised: 09/17/2009] [Accepted: 10/05/2009] [Indexed: 10/20/2022] Open
Abstract
The activity of background K(2P) channels adjusts the resting membrane potential to enable plasticity of excitable cells. Here we have studied the regulation of neuronal K(2P)2.1 (KCNK2, TREK-1) channel activity by resting membrane potential. When heterologously expressed, K(2P)2.1 currents gradually increased at hyperpolarizing potentials and declined at depolarizing potentials, with a midpoint potential of -60 mV. As K(2P) channels are not equipped with an integral voltage sensor, we sought extrinsic cellular components that could convert changes in the membrane electrical field to cellular activity that would indirectly modify K(2P)2.1 currents. We propose that membrane depolarization activated the Gq protein-coupled receptor pathway, in the apparent absence of ligand, resulting in phosphatidylinositol-4,5-bisphosphate (PIP(2)) depletion through the action of phospholipase C. Our results suggest a novel mechanism in which an indirect pathway confers membrane potential regulation onto channels that are not intrinsically voltage sensitive to enhance regulation of neuronal excitability levels.
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Affiliation(s)
- Yifat Segal-Hayoun
- Department of Life Sciences and the Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Bi-directional modulation of bed nucleus of stria terminalis neurons by 5-HT: molecular expression and functional properties of excitatory 5-HT receptor subtypes. Neuroscience 2009; 164:1776-93. [PMID: 19778589 DOI: 10.1016/j.neuroscience.2009.09.028] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 09/05/2009] [Accepted: 09/16/2009] [Indexed: 01/28/2023]
Abstract
Activation of neurons in the anterolateral bed nucleus of the stria terminalis (BNST(ALG)) plays an important role in mediating the behavioral response to stressful and anxiogenic stimuli. Application of 5-HT elicits complex postsynaptic responses in BNST(ALG) neurons, which includes (1) membrane hyperpolarization (5-HT(Hyp)), (2) hyperpolarization followed by depolarization (5-HT(Hyp-Dep)), (3) depolarization (5-HT(Dep)) or (4) no response (5-HT(NR)). We have shown that the inhibitory response is mediated by activation of postsynaptic 5-HT(1A) receptors. Here, we used a combination of in vitro whole-cell patch-clamp recording and single cell reverse transcriptase polymerase chain reaction (RT-PCR) to determine the pharmacological properties and molecular profile of 5-HT receptor subtypes mediating the excitatory response to 5-HT in BNST(ALG) neurons. We show that the depolarizing component of both the 5-HT(Hyp/Dep) and the 5-HT(Dep) response was mediated by activation of 5-HT(2A), 5-HT(2C) and/or 5-HT(7) receptors. Single cell RT-PCR data revealed that 5-HT(7) receptors (46%) and 5-HT(1A) receptors (41%) are the most prevalent receptor subtypes expressed in BNST(ALG) neurons. Moreover, 5-HT receptor subtypes are differentially expressed in type I-III BNST(ALG) neurons. Hence, 5-HT(2C) receptors are almost exclusively expressed by type III neurons, whereas 5-HT(7) receptors are expressed by type I and II neurons, but not type III neurons. Conversely, 5-HT(2A) receptors are found predominantly in type II neurons. Finally, bi-directional modulation of individual neurons occurs only in type I and II neurons. Significantly the distribution of 5-HT receptor subtypes in BNST(ALG) neurons predicted the observed expression pattern of 5-HT responses determined pharmacologically. Together, these results suggest that 5-HT can differentially modulate the excitability of type I-III neurons, and further suggest that bi-directional modulation of BNST(ALG) neurons occurs primarily through an interplay between 5-HT(1A) and 5-HT(7) receptors. Hence, modulation of 5-HT(7) receptor activity in the BNST(ALG) may offer a novel avenue for the design of anxiolytic medications.
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