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Boros-Rausch A, Shynlova O, Lye SJ. A Broad-Spectrum Chemokine Inhibitor Blocks Inflammation-Induced Myometrial Myocyte-Macrophage Crosstalk and Myometrial Contraction. Cells 2021; 11:cells11010128. [PMID: 35011690 PMCID: PMC8750067 DOI: 10.3390/cells11010128] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 12/28/2021] [Accepted: 12/30/2021] [Indexed: 01/10/2023] Open
Abstract
Prophylactic administration of the broad-spectrum chemokine inhibitor (BSCI) FX125L has been shown to suppress uterine contraction, prevent preterm birth (PTB) induced by Group B Streptococcus in nonhuman primates, and inhibit uterine cytokine/chemokine expression in a murine model of bacterial endotoxin (LPS)-induced PTB. This study aimed to determine the mechanism(s) of BSCI action on human myometrial smooth muscle cells. We hypothesized that BSCI prevents infection-induced contraction of uterine myocytes by inhibiting the secretion of pro-inflammatory cytokines, the expression of contraction-associated proteins and disruption of myocyte interaction with tissue macrophages. Myometrial biopsies and peripheral blood were collected from women at term (not in labour) undergoing an elective caesarean section. Myocytes were isolated and treated with LPS with/out BSCI; conditioned media was collected; cytokine secretion was analyzed by ELISA; and protein expression was detected by immunoblotting and immunocytochemistry. Functional gap junction formation was assessed by parachute assay. Collagen lattices were used to examine myocyte contraction with/out blood-derived macrophages and BSCI. We found that BSCI inhibited (1) LPS-induced activation of transcription factor NF-kB; (2) secretion of chemokines (MCP-1/CCL2 and IL-8/CXCL8); (3) Connexin43-mediated intercellular connectivity, thereby preventing myocyte–macrophage crosstalk; and (4) myocyte contraction. BSCI represents novel therapeutics for prevention of inflammation-induced PTB in women.
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Affiliation(s)
- Adam Boros-Rausch
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Suite 6-1017, Toronto, ON M5G 1X5, Canada; (A.B.-R.); (S.J.L.)
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Oksana Shynlova
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Suite 6-1017, Toronto, ON M5G 1X5, Canada; (A.B.-R.); (S.J.L.)
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A1, Canada
- Department of Obstetrics & Gynecology, University of Toronto, Toronto, ON M5S 1A1, Canada
- Correspondence: ; Tel.: +1-416-586-4800 (ext. 5635); Fax: +1-416-586-5116
| | - Stephen James Lye
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Suite 6-1017, Toronto, ON M5G 1X5, Canada; (A.B.-R.); (S.J.L.)
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A1, Canada
- Department of Obstetrics & Gynecology, University of Toronto, Toronto, ON M5S 1A1, Canada
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Li Q, Klein RC, Moore SD. Multiple sources of internal calcium stores mediate ethanol-induced presynaptic inhibitory GABA release in the central nucleus of the amygdala in mice. Psychopharmacology (Berl) 2020; 237:3303-3314. [PMID: 32705289 PMCID: PMC7644111 DOI: 10.1007/s00213-020-05613-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 07/17/2020] [Indexed: 11/27/2022]
Abstract
RATIONALE Ethanol can enhance GABA release in various brain regions via presynaptic mechanisms. However, the presynaptic action of ethanol on inhibitory GABA release is still not well understood. OBJECTIVES Since calcium is required for neurotransmitter release from presynaptic terminals, the purpose of this study was to investigate the role of both internal and external calcium signaling in ethanol-induced enhancement of GABA release within the central amygdala nucleus (CeA) in acute brain slice preparations. METHODS Whole-cell patch clamp electrophysiology was used to record miniature GABAA receptor-mediated inhibitory postsynaptic currents (mIPSCs) from CeA neurons. Ethanol-enhanced mIPSCs were recorded in the presence of antagonists that regulate internal and external calcium-mediated processes. RESULTS Bath-applied ethanol dose-dependently increased the mean frequency of mIPSCs without altering mIPSC amplitude. Ethanol-induced increases in mIPSC frequency were antagonized by dantrolene, 2-APB, and the endoplasmic reticulum calcium pump (SERCA) antagonists thapsigargin and cyclopiazonic acid (CPA). Blocking calcium release from mitochondria or via exocytosis with ruthenium red also attenuated mIPSCs while frequency was not altered in the presence of a non-selective calcium channel blocker cadmium. The L-type calcium blocker nifedipine, but not its analogue nimodipine, blocked ethanol-induced enhancement in CeA neurons. CONCLUSIONS These results demonstrate ethanol-induced presynaptic release of GABA is mediated by internal calcium stores and by disrupting neurotransmitter exocytosis within the CeA, a critical brain area involved in drugs of abuse and alcohol addiction.
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Affiliation(s)
- Qiang Li
- Addictions Division, Department of Psychiatry, Duke University Medical Center, Durham, NC, 27705, USA
- VISN 6 MIRECC, Durham VA Medical Center, Durham, NC, 27705, USA
| | - Rebecca C Klein
- Addictions Division, Department of Psychiatry, Duke University Medical Center, Durham, NC, 27705, USA
- VISN 6 MIRECC, Durham VA Medical Center, Durham, NC, 27705, USA
| | - Scott D Moore
- Addictions Division, Department of Psychiatry, Duke University Medical Center, Durham, NC, 27705, USA.
- VISN 6 MIRECC, Durham VA Medical Center, Durham, NC, 27705, USA.
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Coleman M, Orvis A, Wu TY, Dacanay M, Merillat S, Ogle J, Baldessari A, Kretzer NM, Munson J, Boros-Rausch AJ, Shynlova O, Lye S, Rajagopal L, Adams Waldorf KM. A Broad Spectrum Chemokine Inhibitor Prevents Preterm Labor but Not Microbial Invasion of the Amniotic Cavity or Neonatal Morbidity in a Non-human Primate Model. Front Immunol 2020; 11:770. [PMID: 32425945 PMCID: PMC7203489 DOI: 10.3389/fimmu.2020.00770] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/06/2020] [Indexed: 12/11/2022] Open
Abstract
Leukocyte activation within the chorioamniotic membranes is strongly associated with inflammation and preterm labor (PTL). We hypothesized that prophylaxis with a broad-spectrum chemokine inhibitor (BSCI) would downregulate the inflammatory microenvironment induced by Group B Streptococcus (GBS, Streptococcus agalactiae) to suppress PTL and microbial invasion of the amniotic cavity (MIAC). To correlate BSCI administration with PTL and MIAC, we used a unique chronically catheterized non-human primate model of Group B Streptococcus (GBS)-induced PTL. In the early third trimester (128–138 days gestation; ~29–32 weeks human pregnancy), animals received choriodecidual inoculations of either: (1) saline (N = 6), (2) GBS, 1–5 × 108 colony forming units (CFU)/ml; N = 5), or (3) pre-treatment and daily infusions of a BSCI (10 mg/kg intravenous and intra-amniotic) with GBS (1–5 × 108 CFU/ml; N = 4). We measured amniotic cavity pressure (uterine contraction strength) and sampled amniotic fluid (AF) and maternal blood serially and cord blood at delivery. Cesarean section was performed 3 days post-inoculation or earlier for PTL. Data analysis used Fisher's exact test, Wilcoxon rank sum and one-way ANOVA with Bonferroni correction. Saline inoculation did not induce PTL or infectious sequelae. In contrast, GBS inoculation typically induced PTL (4/5, 80%), MIAC and fetal bacteremia (3/5; 60%). Remarkably, PTL did not occur in the BSCI+GBS group (0/4, 0%; p = 0.02 vs. GBS), despite MIAC and fetal bacteremia in all cases (4/4; 100%). Compared to the GBS group, BSCI prophylaxis was associated with significantly lower cytokine levels including lower IL-8 in amniotic fluid (p = 0.03), TNF-α in fetal plasma (p < 0.05), IFN-α and IL-7 in the fetal lung (p = 0.02) and IL-18, IL-2, and IL-7 in the fetal brain (p = 0.03). Neutrophilic chorioamnionitis was common in the BSCI and GBS groups, but was more severe in the BSCI+GBS group with greater myeloperoxidase staining (granulocyte marker) in the amnion and chorion (p < 0.05 vs. GBS). Collectively, these observations indicate that blocking the chemokine response to infection powerfully suppressed uterine contractility, PTL and the cytokine response, but did not prevent MIAC and fetal pneumonia. Development of PTL immunotherapies should occur in tandem with evaluation for AF microbes and consideration for antibiotic therapy.
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Affiliation(s)
- Michelle Coleman
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Austyn Orvis
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Tsung-Yen Wu
- Department of Obstetrics & Gynecology, University of Washington, Seattle, WA, United States
| | - Matthew Dacanay
- Department of Obstetrics & Gynecology, University of Washington, Seattle, WA, United States
| | - Sean Merillat
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, United States
| | - Jason Ogle
- Washington National Primate Center, University of Washington, Seattle, WA, United States
| | - Audrey Baldessari
- Washington National Primate Center, University of Washington, Seattle, WA, United States
| | - Nicole M Kretzer
- Department of Obstetrics & Gynecology, University of Washington, Seattle, WA, United States
| | - Jeff Munson
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, United States
| | | | - Oksana Shynlova
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Obstetrics & Gynaecology, University of Toronto, Toronto, ON, Canada
| | - Stephen Lye
- Department of Physiology, University of Toronto, Toronto, ON, Canada.,Department of Obstetrics & Gynaecology, University of Toronto, Toronto, ON, Canada
| | - Lakshmi Rajagopal
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, United States.,Department of Pediatrics, University of Washington, Seattle, WA, United States.,Department of Global Health, University of Washington, Seattle, WA, United States
| | - Kristina M Adams Waldorf
- Department of Obstetrics & Gynecology, University of Washington, Seattle, WA, United States.,Department of Global Health, University of Washington, Seattle, WA, United States
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McDonald AJ. Functional neuroanatomy of the basolateral amygdala: Neurons, neurotransmitters, and circuits. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2020; 26:1-38. [PMID: 34220399 PMCID: PMC8248694 DOI: 10.1016/b978-0-12-815134-1.00001-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Alexander J McDonald
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
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5
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Li Q, Zhang Y, Wu N, Yin N, Sun XH, Wang Z. Activation of somatostatin receptor 5 suppresses T-type Ca 2+ channels through NO/cGMP/PKG signaling pathway in rat retinal ganglion cells. Neurosci Lett 2019; 708:134337. [PMID: 31220522 DOI: 10.1016/j.neulet.2019.134337] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/19/2019] [Accepted: 06/17/2019] [Indexed: 11/16/2022]
Abstract
Somatostatin has been shown to modulate a variety of neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Here, effects of sst5 receptor activation on T-type Ca2+ channels in acutely isolated retinal ganglion cells (RGCs) of rats were investigated using whole-cell patch-clamp techniques. The sst5 receptor specific agonist L-817,818 significantly and reversibly suppressed T-type Ca2+ currents, and shifted inactivation curve of the channels toward hyperpolarization direction. The effect of L-817,818 was in a dose-dependent manner, with an IC50 being 8.8 μM. Pertussis toxin-sensitive Gi/o protein mediated intracellular nitric oxide (NO)/cGMP/protein kinase G (PKG) signaling cascade was involved in the L-817,818 effect on Ca2+ currents because pharmacological interference of each of these signaling molecules abolished the L-817,818 effect. In contrast, neither phospholipase C/protein kinase C nor cAMP/protein kinase A signal pathways seemed likely to be involved because the L-817,818 effect persisted when these signaling pathways were blocked by U73122, bisindolylmaleimide IV, chelerythrine chloride, and Rp-cAMP, respectively. These results suggest that activation of sst5 receptors suppresses T-type Ca2+ currents in rat RGCs through intracellular NO/cGMP/PKG signaling pathway, which may provide a potential mechanism for protecting RGCs against injury.
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Affiliation(s)
- Qian Li
- Eye Institute, Eye & ENT Hospital, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Key Laboratory of Myopia (Ministry of Health), Fudan University, Shanghai, 200031, China
| | - Yi Zhang
- Eye Institute, Eye & ENT Hospital, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Key Laboratory of Myopia (Ministry of Health), Fudan University, Shanghai, 200031, China
| | - Na Wu
- Eye Institute, Eye & ENT Hospital, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Key Laboratory of Myopia (Ministry of Health), Fudan University, Shanghai, 200031, China
| | - Ning Yin
- Department of Neurology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Xing-Huai Sun
- Eye Institute, Eye & ENT Hospital, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Key Laboratory of Myopia (Ministry of Health), Fudan University, Shanghai, 200031, China.
| | - Zhongfeng Wang
- Department of Neurology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
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6
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Yavorska I, Wehr M. Somatostatin-Expressing Inhibitory Interneurons in Cortical Circuits. Front Neural Circuits 2016; 10:76. [PMID: 27746722 PMCID: PMC5040712 DOI: 10.3389/fncir.2016.00076] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 09/12/2016] [Indexed: 12/30/2022] Open
Abstract
Cortical inhibitory neurons exhibit remarkable diversity in their morphology, connectivity, and synaptic properties. Here, we review the function of somatostatin-expressing (SOM) inhibitory interneurons, focusing largely on sensory cortex. SOM neurons also comprise a number of subpopulations that can be distinguished by their morphology, input and output connectivity, laminar location, firing properties, and expression of molecular markers. Several of these classes of SOM neurons show unique dynamics and characteristics, such as facilitating synapses, specific axonal projections, intralaminar input, and top-down modulation, which suggest possible computational roles. SOM cells can be differentially modulated by behavioral state depending on their class, sensory system, and behavioral paradigm. The functional effects of such modulation have been studied with optogenetic manipulation of SOM cells, which produces effects on learning and memory, task performance, and the integration of cortical activity. Different classes of SOM cells participate in distinct disinhibitory circuits with different inhibitory partners and in different cortical layers. Through these disinhibitory circuits, SOM cells help encode the behavioral relevance of sensory stimuli by regulating the activity of cortical neurons based on subcortical and intracortical modulatory input. Associative learning leads to long-term changes in the strength of connectivity of SOM cells with other neurons, often influencing the strength of inhibitory input they receive. Thus despite their heterogeneity and variability across cortical areas, current evidence shows that SOM neurons perform unique neural computations, forming not only distinct molecular but also functional subclasses of cortical inhibitory interneurons.
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Affiliation(s)
| | - Michael Wehr
- Institute of Neuroscience and Department of Psychology, University of OregonEugene, OR, USA
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7
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Deng QQ, Sheng WL, Zhang G, Weng SJ, Yang XL, Zhong YM. Signalling mechanism for somatostatin receptor 5-mediated suppression of AMPA responses in rat retinal ganglion cells. Neuropharmacology 2016; 107:215-226. [DOI: 10.1016/j.neuropharm.2016.03.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 01/25/2016] [Accepted: 03/02/2016] [Indexed: 01/21/2023]
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8
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Bou Farah L, Bowman BR, Bokiniec P, Karim S, Le S, Goodchild AK, McMullan S. Somatostatin in the rat rostral ventrolateral medulla: Origins and mechanism of action. J Comp Neurol 2015; 524:323-42. [PMID: 26131686 DOI: 10.1002/cne.23846] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 06/22/2015] [Accepted: 06/23/2015] [Indexed: 01/24/2023]
Abstract
Somatostatin (SST) or agonists of the SST-2 receptor (sst2 ) in the rostral ventrolateral medulla (RVLM) lower sympathetic nerve activity, arterial pressure, and heart rate, or when administered within the Bötzinger region, evoke apneusis. Our aims were to describe the mechanisms responsible for the sympathoinhibitory effects of SST on bulbospinal neurons and to identify likely sources of RVLM SST release. Patch clamp recordings were made from bulbospinal RVLM neurons (n = 31) in brainstem slices prepared from juvenile rat pups. Overall, 58% of neurons responded to SST, displaying an increase in conductance that reversed at -93 mV, indicative of an inwardly rectifying potassium channel (GIRK) mechanism. Blockade of sst2 abolished this effect, but application of tetrodotoxin did not, indicating that the SST effect is independent of presynaptic activity. Fourteen bulbospinal RVLM neurons were recovered for immunohistochemistry; nine were SST-insensitive and did not express sst2a . Three out of five responsive neurons were sst2a -immunoreactive. Neurons that contained preprosomatostatin mRNA and cholera-toxin-B retrogradely transported from the RVLM were detected in: paratrigeminal nucleus, lateral parabrachial nucleus, Kölliker-Fuse nucleus, ventrolateral periaqueductal gray area, central nucleus of the amygdala, sublenticular extended amygdala, interstitial nucleus of the posterior limb of the anterior commissure nucleus, and bed nucleus of the stria terminalis. Thus, those brain regions are putative sources of endogenous SST release that, when activated, may evoke sympathoinhibitory effects via interactions with subsets of sympathetic premotor neurons that express sst2 .
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Affiliation(s)
- Lama Bou Farah
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Belinda R Bowman
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Phil Bokiniec
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Shafinaz Karim
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Sheng Le
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Ann K Goodchild
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
| | - Simon McMullan
- Australian School of Advanced Medicine, Macquarie University, 2109, NSW, Australia
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9
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Chen W, Ke JB, Wu HJ, Miao Y, Li F, Yang XL, Wang Z. Somatostatin receptor-mediated suppression of gabaergic synaptic transmission in cultured rat retinal amacrine cells. Neuroscience 2014; 273:118-27. [PMID: 24846611 DOI: 10.1016/j.neuroscience.2014.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 01/03/2023]
Abstract
Somatostatin (SRIF) modulates neurotransmitter release by activating the specific receptors (sst1-sst5). Our previous study showed that sst5 receptors are expressed in rat retinal GABAergic amacrine cells. Here, we investigated modulation of GABA release by SRIF in cultured amacrine cells, using patch-clamp techniques. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in the amacrine cells was significantly reduced by SRIF, which was partially reversed by BIM 23056, an sst5 receptor antagonist, and was further rescued by addition of CYN-154806, an sst2 receptor antagonist. Both nimodipine, an L-type Ca2+ channel blocker, and ω-conotoxin GVIA, an N-type Ca2+ channel blocker, suppressed the sIPSC frequency, and in the presence of nimodipine and ω-conotoxin GVIA, SRIF failed to further suppress the sIPSC frequency. Extracellular application of forskolin, an activator of adenylate cyclase, increased the sIPSC frequency, while the membrane permeable protein kinase A (PKA) inhibitor Rp-cAMP reduced it, and in the presence of Rp-cAMP, SRIF did not change sIPSCs. However, SRIF persisted to suppress the sIPSCs in the presence of KT5823, a protein kinase G (PKG) inhibitor. Moreover, pre-incubation with Bis IV, a protein kinase C (PKC) inhibitor, or pre-application of xestospongin C, an inositol 1,4,5-trisphosphate receptor (IP3R) inhibitor, SRIF still suppressed the sIPSC frequency. All these results suggest that SRIF suppresses GABA release from the amacrine cells by inhibiting presynaptic Ca2+ channels, in part through activating sst5/sst2 receptors, a process that is mediated by the intracellular cAMP-PKA signaling pathway.
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Affiliation(s)
- W Chen
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - J B Ke
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - H J Wu
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Y Miao
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - F Li
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - X L Yang
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Z Wang
- Institutes of Brain Science, Institute of Neurobiology and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China.
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Abstract
The peptide hormone somatostatin (SST) is produced in the brain, the gut, and in δ-cells in pancreatic islets of Langerhans. SST secretion from δ-cells is stimulated by glucose, amino acids, and glucagon-like peptide-1. Exogenous SST strongly inhibits the secretion of the blood glucose-regulating hormones insulin and glucagon from pancreatic β-cells and α-cells, respectively. Endogenous SST secreted from δ-cells is a paracrine regulator of insulin and glucagon secretion, although the exact physiological significance of this regulation is unclear. Secreted SST binds to specific receptors (SSTRs), which are coupled to Gi/o proteins. In both β- and α-cells, activation of SSTRs suppresses hormone secretion by reducing cAMP levels, inhibiting electrical activity, decreasing Ca²⁺ influx through voltage-gated Ca²⁺ channels and directly reducing exocytosis in a Ca²⁺ and cAMP-independent manner. In rodents, β-cells express predominantly SSTR5, whereas α-cells express SSTR2. In human islets, SSTR2 is the dominant receptor in both β- and α-cells, but other isoforms also contribute to the SST effects. Evidence from rodent models suggests that SST secretion from δ-cells is dysregulated in diabetes mellitus, which may contribute to the metabolic disturbances in this disease. SST analogues are currently used for the treatment of hyperinsulinism and other endocrine disorders, including acromegaly and Cushing's syndrome.
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Affiliation(s)
- Matthias Braun
- Alberta Diabetes Institute, Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
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Peptide receptor targeting in cancer: the somatostatin paradigm. INTERNATIONAL JOURNAL OF PEPTIDES 2013; 2013:926295. [PMID: 23476673 PMCID: PMC3582104 DOI: 10.1155/2013/926295] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 12/10/2012] [Accepted: 12/28/2012] [Indexed: 02/06/2023]
Abstract
Peptide receptors involved in pathophysiological processes represent promising therapeutic targets. Neuropeptide somatostatin (SST) is produced by specialized cells in a large number of human organs and tissues. SST primarily acts as inhibitor of endocrine and exocrine secretion via the activation of five G-protein-coupled receptors, named sst1–5, while in central nervous system, SST acts as a neurotransmitter/neuromodulator, regulating locomotory and cognitive functions. Critical points of SST/SST receptor biology, such as signaling pathways of individual receptor subtypes, homo- and heterodimerization, trafficking, and cross-talk with growth factor receptors, have been extensively studied, although functions associated with several pathological conditions, including cancer, are still not completely unraveled. Importantly, SST exerts antiproliferative and antiangiogenic effects on cancer cells in vitro, and on experimental tumors in vivo. Moreover, SST agonists are clinically effective as antitumor agents for pituitary adenomas and gastro-pancreatic neuroendocrine tumors. However, SST receptors being expressed by tumor cells of various tumor histotypes, their pharmacological use is potentially extendible to other cancer types, although to date no significant results have been obtained. In this paper the most recent findings on the expression and functional roles of SST and SST receptors in tumor cells are discussed.
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Kailey B, van de Bunt M, Cheley S, Johnson PR, MacDonald PE, Gloyn AL, Rorsman P, Braun M. SSTR2 is the functionally dominant somatostatin receptor in human pancreatic β- and α-cells. Am J Physiol Endocrinol Metab 2012; 303:E1107-16. [PMID: 22932785 PMCID: PMC3492856 DOI: 10.1152/ajpendo.00207.2012] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Somatostatin-14 (SST) inhibits insulin and glucagon secretion by activating G protein-coupled somatostatin receptors (SSTRs), of which five isoforms exist (SSTR1-5). In mice, the effects on pancreatic β-cells are mediated by SSTR5, whereas α-cells express SSTR2. In both cell types, SSTR activation results in membrane hyperpolarization and suppression of exocytosis. Here, we examined the mechanisms by which SST inhibits secretion from human β- and α-cells and the SSTR isoforms mediating these effects. Quantitative PCR revealed high expression of SSTR2, with lower levels of SSTR1, SSTR3, and SSTR5, in human islets. Immunohistochemistry showed expression of SSTR2 in both β- and α-cells. SST application hyperpolarized human β-cells and inhibited action potential firing. The membrane hyperpolarization was unaffected by tolbutamide but antagonized by tertiapin-Q, a blocker of G protein-gated inwardly rectifying K⁺ channels (GIRK). The effect of SST was mimicked by an SSTR2-selective agonist, whereas a SSTR5 agonist was marginally effective. SST strongly (>70%) reduced depolarization-evoked exocytosis in both β- and α-cells. A slightly weaker inhibition was observed in both cell types after SSTR2 activation. SSTR3- and SSTR1-selective agonists moderately reduced the exocytotic responses in β- and α-cells, respectively, whereas SSTR4- and SSTR5-specific agonists were ineffective. SST also reduced voltage-gated P/Q-type Ca²⁺ currents in β-cells, but normalization of Ca²⁺ influx to control levels by prolonged depolarizations only partially restored exocytosis. We conclude that SST inhibits secretion from both human β- and α-cells by activating GIRK and suppressing electrical activity, reducing P/Q-type Ca²⁺ currents, and directly inhibiting exocytosis. These effects are mediated predominantly by SSTR2 in both cell types.
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Affiliation(s)
- Balrik Kailey
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, University of Oxford, Oxford, United Kingdom
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Patel YC, Liu J, Galanopoulou A, Papachristou DN. Production, Action, and Degradation of Somatostatin. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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14
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Chieng B, Christie MJ. Somatostatin and nociceptin inhibit neurons in the central nucleus of amygdala that project to the periaqueductal grey. Neuropharmacology 2010; 59:425-30. [PMID: 20541564 DOI: 10.1016/j.neuropharm.2010.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/01/2010] [Accepted: 06/02/2010] [Indexed: 01/08/2023]
Abstract
The central nucleus of amygdala (CeA) plays an important role in modulation of the descending antinociceptive pathways. Using whole-cell patch clamp recordings from brain slices, we found that CeA neurons responded to the endogenous ligands somatostatin (SST) and nociceptin/orphanin FQ (OFQ) via an increased K-conductance. Co-application with selective antagonists suggested that SST and OFQ act on SSTR2 and ORL1 receptors, respectively. Taking account of anatomical localisation of recorded neurons, the present study showed that many responsive neurons were located within the medial subdivision of CeA and all CeA projection neurons to the midbrain periaqueductal grey invariably responded to these peptides. Randomly selected agonist-responsive neurons in CeA predominantly classified physiologically as low-threshold spiking neurons. The similarity of SST, OFQ and, as previously reported, opioid responsiveness in a sub-population of CeA neurons suggests converging roles of these peptides to inhibit the activity of projections from CeA to vlPAG, and potentially similar antinociceptive actions in this pathway.
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Affiliation(s)
- Billy Chieng
- Brain & Mind Research Institute, University of Sydney, 100 Mallett St, Camperdown, NSW 2050, Australia.
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15
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Somatostatin, Alzheimer's disease and cognition: An old story coming of age? Prog Neurobiol 2009; 89:153-61. [DOI: 10.1016/j.pneurobio.2009.07.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 04/27/2009] [Accepted: 07/02/2009] [Indexed: 12/21/2022]
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16
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Viollet C, Lepousez G, Loudes C, Videau C, Simon A, Epelbaum J. Somatostatinergic systems in brain: networks and functions. Mol Cell Endocrinol 2008; 286:75-87. [PMID: 17997029 DOI: 10.1016/j.mce.2007.09.007] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 09/10/2007] [Accepted: 09/19/2007] [Indexed: 12/21/2022]
Abstract
Somatostatin is abundantly expressed in mammalian brain. The peptide binds with high affinity to six somatostatin receptors, sst1, sst2A and B, sst3 to 5, all belonging to the G-protein-coupled receptor family. Recent advances in the neuroanatomy of somatostatin neurons and cellular distribution of sst receptors shed light on their functional roles in the neuronal network. Beside their initially described neuroendocrine role, somatostatin systems subserve neuromodulatory roles in the brain, influencing motor activity, sleep, sensory processes and cognitive functions, and are altered in brain diseases like affective disorders, epilepsia and Alzheimer's disease.
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17
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Pan HL, Wu ZZ, Zhou HY, Chen SR, Zhang HM, Li DP. Modulation of pain transmission by G-protein-coupled receptors. Pharmacol Ther 2007; 117:141-61. [PMID: 17959251 DOI: 10.1016/j.pharmthera.2007.09.003] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Accepted: 09/07/2007] [Indexed: 01/17/2023]
Abstract
The heterotrimeric G-protein-coupled receptors (GPCR) represent the largest and most diverse family of cell surface receptors and proteins. GPCR are widely distributed in the peripheral and central nervous systems and are one of the most important therapeutic targets in pain medicine. GPCR are present on the plasma membrane of neurons and their terminals along the nociceptive pathways and are closely associated with the modulation of pain transmission. GPCR that can produce analgesia upon activation include opioid, cannabinoid, alpha2-adrenergic, muscarinic acetylcholine, gamma-aminobutyric acidB (GABAB), groups II and III metabotropic glutamate, and somatostatin receptors. Recent studies have led to a better understanding of the role of these GPCR in the regulation of pain transmission. Here, we review the current knowledge about the cellular and molecular mechanisms that underlie the analgesic actions of GPCR agonists, with a focus on their effects on ion channels expressed on nociceptive sensory neurons and on synaptic transmission at the spinal cord level.
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Affiliation(s)
- Hui-Lin Pan
- Department of Anesthesiology and Pain Medicine, The University of Texas M.D. Anderson Cancer Center, Program in Neuroscience, The University of Texas Graduate School of Biomedical Sciences, Houston, TX 77225, United States.
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18
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Cervia D, Bagnoli P. An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology. Pharmacol Ther 2007; 116:322-41. [PMID: 17719647 DOI: 10.1016/j.pharmthera.2007.06.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 06/28/2007] [Indexed: 12/20/2022]
Abstract
The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.
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Affiliation(s)
- Davide Cervia
- Department of Environmental Sciences, University of Tuscia, largo dell'Università snc, blocco D, 01100 Viterbo, Italy.
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19
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Kim DS, Kwak SE, Kim JE, Kim JS, Won MH, Kang TC. The selective effects of somatostatin- and GABA-mediated transmissions on voltage gated Ca2+ channel immunoreactivity in the gerbil hippocampus. Brain Res 2006; 1115:200-8. [PMID: 16920080 DOI: 10.1016/j.brainres.2006.07.076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 07/13/2006] [Accepted: 07/24/2006] [Indexed: 10/24/2022]
Abstract
To identify whether altered expressions of voltage gated Ca(2+) channel (VGCC) are linked to inhibitory transmission abnormalities in the gerbil hippocampus, we investigated the effects of GABA receptor or somatostatin receptor (SST) antagonists/agonists on VGCC immunoreactivity in vivo. VGCC immunoreactivities in the hippocampus were significantly higher in seizure sensitive (SS) gerbils than in seizure resistant (SR) gerbils. P/Q-type VGCC immunoreactivity in the gerbil hippocampus was reduced by enhancement in GABA(A) and GABA(B) receptor-mediated transmission, but not by SST-mediated transmission. N-type VGCC immunoreactivity was reduced only by a SST agonist, whereas L-type (alpha1C) VGCC immunoreactivity was reduced only by a GABA(A) receptor agonist, and L-type (alpha1D) VGCC immunoreactivity was modulated by the GABA(B) receptor acting drugs. These findings provide a comprehensive description of the differential responses of VGCC subunits to alteration in GABAergic or somatostatinergic transmission. These findings also suggest that up-regulated VGCC immunoreactivity may be consequence of the neuronal excitability caused by a reduction in inhibitory neurotransmission in the gerbil hippocampus.
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MESH Headings
- Animals
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Channels, N-Type/drug effects
- Calcium Channels, N-Type/metabolism
- Calcium Channels, P-Type/drug effects
- Calcium Channels, P-Type/metabolism
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Disease Models, Animal
- Epilepsy/chemically induced
- Epilepsy/metabolism
- Epilepsy/physiopathology
- Epilepsy, Temporal Lobe/metabolism
- Epilepsy, Temporal Lobe/physiopathology
- GABA Agonists/pharmacology
- GABA Antagonists/pharmacology
- GABA-A Receptor Agonists
- GABA-A Receptor Antagonists
- GABA-B Receptor Agonists
- GABA-B Receptor Antagonists
- Gerbillinae
- Hippocampus/drug effects
- Hippocampus/metabolism
- Hippocampus/physiopathology
- Immunohistochemistry
- Neural Inhibition/drug effects
- Neural Inhibition/physiology
- Neurons/drug effects
- Neurons/metabolism
- Receptors, GABA-A/metabolism
- Receptors, Somatostatin/agonists
- Receptors, Somatostatin/antagonists & inhibitors
- Receptors, Somatostatin/metabolism
- Somatostatin/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- Duk-Soo Kim
- Department of Anatomy, College of Medicine, Hallym University, Chunchon, Kangwon-Do 200-702, South Korea
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20
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Young Shim E, Jung Kim H, Kim MJ, Rhie DJ, Jo YH, Kim MS, June Hahn S, Lee MY, Yoon SH. Desensitization of somatostatin-induced inhibition of low extracellular magnesium concentration-induced calcium spikes in cultured rat hippocampal neurons. Brain Res 2006; 1111:61-71. [PMID: 16879804 DOI: 10.1016/j.brainres.2006.06.081] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Revised: 06/20/2006] [Accepted: 06/27/2006] [Indexed: 11/21/2022]
Abstract
Neuronal excitability is inhibited by somatostatin, which might play important roles in seizure and neuroprotection. The possibility of whether the effect of somatostatin on neurotransmission is susceptible to desensitization was investigated. We tested the effects of prolonged exposure to somatostatin on 0.1 mM extracellular Mg(2+) concentration ([Mg(2+)](o))-induced intracellular free Ca(2+) concentration ([Ca(2+)](i)) spikes in cultured rat hippocampal neurons using fura-2-based microfluorimetry. Reducing [Mg(2+)](o) to 0.1 mM elicited repetitive [Ca(2+)](i) spikes. These [Ca(2+)](i) spikes were inhibited by exposure to somatostatin-14. The inhibitory effects of somatostatin were blocked by pretreatment with pertussis toxin (PTX, 100 ng/ml) for 18-24 h. Prolonged exposure to somatostatin induced a desensitization of the somatostatin-induced inhibition of [Ca(2+)](i) spikes in a concentration-dependent manner. The somatostatin-induced desensitization was retarded by the nonspecific protein kinase C (PKC) inhibitor staurosporin (100 nM) or chronic treatment with phorbol dibutyrate (1 microM) for 24 h, but not by the protein kinase A inhibitor KT5720. The desensitization was significantly retarded by the novel PKCepsilon translocation inhibitor peptide (1 microM). In addition, suramin (3 microM), an inhibitor of G-protein-coupled receptor kinase 2 (GRK2), caused a reduction in the desensitization. After tetrodotoxin (TTX, 1 microM) completely blocked the low [Mg(2+)](o)-induced [Ca(2+)](i) spikes, glutamate-induced [Ca(2+)](i) transients were slightly inhibited by somatostatin and the inhibition was desensitized by prolonged exposure to somatostatin. These results indicate that the prolonged activation of somatostatin receptors induces the desensitization of somatostatin-induced inhibition on low [Mg(2+)](o)-induced [Ca(2+)](i) spikes through the activation of GRK2 and partly a novel PKCepsilon in cultured rat hippocampal neurons.
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Affiliation(s)
- Eun Young Shim
- Department of Physiology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, South Korea
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21
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Endoh T. Pharmacological characterization of inhibitory effects of postsynaptic opioid and cannabinoid receptors on calcium currents in neonatal rat nucleus tractus solitarius. Br J Pharmacol 2006; 147:391-401. [PMID: 16402042 PMCID: PMC1616990 DOI: 10.1038/sj.bjp.0706623] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Accepted: 11/15/2005] [Indexed: 12/19/2022] Open
Abstract
1. The profile of opioid and cannabinoid receptors in neurons of the nucleus tractus solitarius (NTS) has been studied using the whole-cell configuration of the patch clamp technique. 2. Experiments with selective agonists and antagonists of opioid, ORL and cannabinoid receptors indicated that mu-opioid, kappa-opioid, ORL-1 and CB1, but not delta-opioid, receptors inhibit VDCCs in NTS. 3. Application of [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO; mu-opioid receptor agonist), Orphanin FQ (ORL-1 receptor agonist) and WIN55,122 (CB1 receptor agonist) caused inhibition of I(Ba) in a concentration-dependent manner, with IC50's of 390 nM, 220 nM and 2.2 microM, respectively. 4. Intracellular dialysis of the G(i)-protein antibody attenuated DAMGO-, Orphanin FQ- and WIN55,122-induced inhibition of I(Ba). 5. Both pretreatment with adenylate cyclase inhibitor and intracellular dialysis of the protein kinase A (PKA) inhibitor attenuated WIN55,122-induced inhibition of I(Ba) but not DAMGO- and Orphanin FQ-induced inhibition. 6. Mainly N- and P/Q-type VDCCs were inhibited by both DAMGO and Orphanin FQ, while L-type VDCCs were inhibited by WIN55,122. 7. These results suggest that mu- and kappa-opioid receptors and ORL-1 receptor inhibit N- and P/Q-type VDCCs via G alpha(i)-protein betagamma subunits, whereas CB1 receptors inhibit L-type VDCCs via G alpha(i)-proteins involving PKA in NTS.
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MESH Headings
- Animals
- Animals, Newborn
- Calcium/physiology
- Calcium Channels/classification
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Channels, P-Type/drug effects
- Calcium Channels, P-Type/metabolism
- Calcium Channels, Q-Type/drug effects
- Calcium Channels, Q-Type/metabolism
- Cannabinoid Receptor Antagonists
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Kinetics
- Narcotic Antagonists
- Opioid Peptides/pharmacology
- Patch-Clamp Techniques
- Rats
- Rats, Wistar
- Receptors, Cannabinoid/drug effects
- Receptors, Cannabinoid/genetics
- Receptors, Opioid/agonists
- Receptors, Opioid/drug effects
- Receptors, Opioid/genetics
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/drug effects
- Solitary Nucleus/cytology
- Solitary Nucleus/metabolism
- Nociceptin
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Affiliation(s)
- Takayuki Endoh
- Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan.
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22
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Muller JF, Mascagni F, McDonald AJ. Postsynaptic targets of somatostatin-containing interneurons in the rat basolateral amygdala. J Comp Neurol 2006; 500:513-29. [PMID: 17120289 DOI: 10.1002/cne.21185] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The basolateral amygdala contains several subpopulations of inhibitory interneurons that can be distinguished on the basis of their content of calcium-binding proteins or peptides. Although previous studies have shown that interneuronal subpopulations containing parvalbumin (PV) or vasoactive intestinal peptide (VIP) innervate distinct postsynaptic domains of pyramidal cells as well as other interneurons, very little is known about the synaptic outputs of the interneuronal subpopulation that expresses somatostatin (SOM). The present study utilized dual-labeling immunocytochemical techniques at the light and electron microscopic levels to analyze the innervation of pyramidal cells, PV+ interneurons, and VIP+ interneurons in the anterior basolateral amygdalar nucleus (BLa) by SOM+ axon terminals. Pyramidal cell somata and dendrites were selectively labeled with antibodies to calcium/calmodulin-dependent protein kinase II (CaMK); previous studies have shown that the vast majority of dendritic spines, whether CAMK+ or not, arise from pyramidal cells. Almost all SOM+ axon terminals formed symmetrical synapses. The main postsynaptic targets of SOM+ terminals were small-caliber CaMK+ dendrites and dendritic spines, some of which were CaMK+. These SOM+ synapses with dendrites were often in close proximity to asymmetrical (excitatory) synapses to these same structures formed by unlabeled terminals. Few SOM+ terminals formed synapses with CaMK+ pyramidal cell somata or large-caliber (proximal) dendrites. Likewise, only 15% of SOM+ terminals formed synapses with PV+, VIP+, or SOM+ interneurons. These findings suggest that inhibitory inputs from SOM+ interneurons may interact with excitatory inputs to pyramidal cell distal dendrites in the BLa. These interactions might affect synaptic plasticity related to emotional learning.
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Affiliation(s)
- Jay F Muller
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina 29208, USA
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23
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Tokita K, Inoue T, Yamazaki S, Wang F, Yamaji T, Matsuoka N, Mutoh S. FK962, a novel enhancer of somatostatin release, exerts cognitive-enhancing actions in rats. Eur J Pharmacol 2005; 527:111-20. [PMID: 16325809 DOI: 10.1016/j.ejphar.2005.10.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Revised: 10/11/2005] [Accepted: 10/18/2005] [Indexed: 11/15/2022]
Abstract
FK962 (N-(1-acetylpiperidin-4-yl)-4-fluorobenzamide) is a derivative of FK960 (N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate), with putative anti-dementia properties. Here, we wanted to determine whether FK962 retained the ability of the parent compound to both facilitate somatostatinergic nerve activity in hippocampal neurons and to ameliorate cognitive dysfunction in rat models. FK962 (10(-9) - 10(- 6) M) significantly enhanced high K+-evoked somatostatin release from rat hippocampal slices. FK962 also significantly reduced somatostatin-induced inhibition of Ca2+ channels at 10(-9) - 10(-7) M in single rat hippocampal neurons using whole-cell patch-clamp. Furthermore, administration of FK962 (0.032-3.2 mg/kg, i.p.) significantly ameliorated memory deficits in passive avoidance task in animal models: scopolamine-treated rats, nucleus basalis magnocellularis-lesioned rats and aged rats. FK962 (0.01- 1) mg/kg, i.p.) significantly improved spatial memory deficits induced by nucleus basalis magnocellularis-lesion in water maze task. These results suggest that FK962 ameliorates cognitive impairment in rats via activation of the somatostatinergic nervous system in the hippocampus, indicating that FK962 could be a potent cognitive enhancer and therefore might be of therapeutic value for cognitive disorders such as Alzheimer's disease.
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Affiliation(s)
- Kenichi Tokita
- Pharmacology Research Labs., Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan.
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24
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Meis S, Sosulina L, Schulz S, Höllt V, Pape HC. Mechanisms of somatostatin-evoked responses in neurons of the rat lateral amygdala. Eur J Neurosci 2005; 21:755-62. [PMID: 15733093 DOI: 10.1111/j.1460-9568.2005.03922.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of somatostatin in the rat lateral amygdala (LA) in vitro were investigated through whole cell recording techniques. Somatostatin induced an inwardly rectifying K+ current in approximately 98% of LA projection neurons. Half-maximal effects were obtained by 189 nM somatostatin. The effects of somatostatin were insensitive to tetrodotoxin, reduced by Ba2+, occluded or abolished by the presence of nonhydrolysable GTP or GDP analogues, respectively, and blocked or mimicked by a somatostatin receptor type 2 antagonist (BIM-23627) or somatostatin receptor type 2 agonist (L-779,976), respectively, while somatostatin receptor type 1, 3 and 4 agonists were ineffective (L-797,591, L-796,778, L-803,087). Responses to somatostatin were associated with membrane hyperpolarization and decrease in input resistance, resulting in a dampening of cell excitability. It is suggested that these cellular mechanisms contribute to the role of somatostatin in decreasing anxiety behaviour as well as to anticonvulsant and antiepileptogenic actions of somatostatin or somatostatin agonists in the amygdala.
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Affiliation(s)
- Susanne Meis
- Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke-Universität, Leipziger Str. 44, D-39120 Magdeburg, Germany.
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25
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Kang TC, Kim DS, Yoo KY, Hwang IK, Kwak SE, Kim JE, Jung JY, Won MH, Suh JG, Oh YS. Elevated voltage-gated Ca2+ channel immunoreactivities in the hippocampus of seizure-prone gerbil. Brain Res 2005; 1029:168-78. [PMID: 15542071 DOI: 10.1016/j.brainres.2004.09.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2004] [Indexed: 11/20/2022]
Abstract
In present study, we investigated voltage-gated Ca2+ channel (VGCC) expressions in the hippocampus of the Mongolian gerbil and its association with different sequelae of spontaneous seizures, in an effort to identify the epileptogenesis in this animal. In the hippocampus of pre-seizure seizure sensitive (SS) gerbils, VGCC subunit expressions were significantly elevated, as compared with seizure-resistant (SR) gerbils. In 3 h postictal group, the alteration of VGCC expressions showed regional- and neuronal-specific manners; VGCC immunoreactivities in principal neurons were markedly decreased; however, their immunoreactivities in interneurons were significantly elevated. These results are the first comprehensive description of the distribution of VGCC immunoreactivities in the normal and epileptic hippocampus of gerbils, and suggest that these alterations in the hippocampus of the SS gerbil may be related with tissue excitability and have a role in modulating recurrent excitation following seizures.
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Affiliation(s)
- Tae-Cheon Kang
- Department of Anatomy, College of Medicine, Hallym University, Chunchon, Kangwon-Do 200-702, South Korea.
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26
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Wang F, Matsuoka N, Mutoh S, Kaneko S. Modulation of Ca2+ channel currents by a novel antidementia drug N-(4-Acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960) in rat hippocampal neurons. J Pharmacol Exp Ther 2003; 308:120-6. [PMID: 14569070 DOI: 10.1124/jpet.103.057687] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
N-(4-Acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960), a novel antidementia drug, has been demonstrated to ameliorate memory deficits in various experimental models of dementia. This drug selectively increases somatostatin release from hippocampal slices and augments long-term potentiation (LTP) in the CA3 area of the hippocampus. In the present study, the effects of FK960 on voltage-activated Ca2+ channels were investigated in acutely isolated rat hippocampal neurons, using whole-cell patch-clamp technique to clarify the cellular mode of action of FK960. Application of somatostatin significantly reduced Ca2+ currents via G protein-coupled signaling pathways. This inhibitory effect was significantly abolished by FK960 when applied in combination. In contrast, FK960 showed only modest inhibition on the reduction in Ca2+ currents produced by baclofen, an agonist of GABAB receptor. Intracellular application of the protein kinase inhibitor H-7 did not alter somatostatin-induced inhibition and had no significant effect on blockade by FK960. In addition, application of FK960 alone produced modest but apparent increases in Ca2+ currents without significant changes in the activation kinetics of the channels. The dose-response relationship on calcium current enhancement was bell-shaped with a maximum effect at 0.1 microM FK960, the same concentration as that for increasing on somatostatin release and CA3-LTP. These results show that FK960 reverses G protein-dependent inhibition of Ca2+ currents by somatostatin in hippocampal neurons. Enhancement of Ca2+ currents by FK960 may be due to its modulatory actions on Ca2+ channels, rather than removal of G protein-inhibited tonic currents. Together, these mechanisms may be involved in the selective effects of FK960 on somatostatin release, excitatory transmission, and synaptic plasticity in the hippocampus.
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Affiliation(s)
- Feng Wang
- Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Kashima, Osaka 532-8514, Japan
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27
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Allen JP, Hathway GJ, Clarke NJ, Jowett MI, Topps S, Kendrick KM, Humphrey PPA, Wilkinson LS, Emson PC. Somatostatin receptor 2 knockout/lacZ knockin mice show impaired motor coordination and reveal sites of somatostatin action within the striatum. Eur J Neurosci 2003; 17:1881-95. [PMID: 12752788 DOI: 10.1046/j.1460-9568.2003.02629.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The peptide somatostatin can modulate the functional output of the basal ganglia. The exact sites and mechanisms of this action, however, are poorly understood, and the physiological context in which somatostatin acts is unknown. Somatostatin acts as a neuromodulator via a family of five 7-transmembrane G protein-coupled receptors, SSTR1-5, one of which, SSTR2, is known to be functional in the striatum. We have investigated the role of SSTR2 in basal ganglia function using mice in which Sstr2 has been inactivated and replaced by the lacZ reporter gene. Analysis of Sstr2lacZ expression in the brain by beta-galactosidase histochemistry demonstrated a widespread pattern of expression. By comparison to previously published in situ hybridization and immunohistochemical data, Sstr2lacZ expression was shown to accurately recapitulate that of Sstr2 and thus provided a highly sensitive model to investigate cell-type-specific expression of Sstr2. In the striatum, Sstr2 expression was identified in medium spiny projection neurons restricted to the matrix compartment and in cholinergic interneurons. Sstr2 expression was not detected in any other nuclei of the basal ganglia except for a sparse number of nondopaminergic neurons in the substantia nigra. Microdialysis in the striatum showed Sstr2-null mice were selectively refractory to somatostatin-induced dopamine and glutamate release. In behavioural tests, Sstr2-null mice showed normal levels of locomotor activity and normal coordination in undemanding tasks. However, in beam-walking, a test of fine motor control, Sstr2-null mice were severely impaired. Together these data implicate an important neuromodulatory role for SSTR2 in the striatum.
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Affiliation(s)
- Jeremy P Allen
- Department of Neurobiology, The Babraham Institute, Babraham, Cambridge, CB2 AT, UK.
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28
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Lin CY, Varma MG, Joubel A, Madabushi S, Lichtarge O, Barber DL. Conserved motifs in somatostatin, D2-dopamine, and alpha 2B-adrenergic receptors for inhibiting the Na-H exchanger, NHE1. J Biol Chem 2003; 278:15128-35. [PMID: 12566440 DOI: 10.1074/jbc.m212315200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor subtypes within families of G protein-coupled receptors that are activated by similar ligands can regulate distinct intracellular effectors. We identified conserved motifs within intracellular domains 2 and 3 of selective subtypes of several G protein-coupled receptor families that confer coupling to the Na-H exchanger, NHE1. A T(s,p)V motif within intracellular domain 2 and a QQ(r) motif within intracellular domain 3 are shared by the somatostatin receptor subtypes SSTR1, -3, and -4, which couple to the inhibition of NHE1, but not by SSTR2 and -5, which do not signal to NHE1. Only the collective substitution of cognate SSTR2 residues with these two motifs conferred the ability of mutant SSTR2 to inhibit NHE1. Both motifs are present in D(2)-dopamine receptors, which inhibit NHE1, and in alpha(2B)-adrenergic receptors, which couple to the inhibition of NHE1, but not in alpha(2A)-adrenergic receptors, which do not regulate NHE1. These findings indicate that motifs shared by different subfamilies of G protein-coupled receptors, but not necessarily by receptor subtypes within a subfamily, can confer coupling to a common effector.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Conserved Sequence
- Membrane Proteins
- Rats
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/metabolism
- Receptors, Dopamine D2/chemistry
- Receptors, Dopamine D2/metabolism
- Receptors, Somatostatin/chemistry
- Receptors, Somatostatin/metabolism
- Sequence Alignment
- Signal Transduction
- Sodium-Hydrogen Exchangers/antagonists & inhibitors
- Sodium-Hydrogen Exchangers/metabolism
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Affiliation(s)
- Chin-Yu Lin
- University of California, San Francisco, San Francisco, California 94143, USA
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29
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Oz M, Renaud LP. Angiotensin AT(1)-receptors depolarize neonatal spinal motoneurons and other ventral horn neurons via two different conductances. J Neurophysiol 2002; 88:2857-63. [PMID: 12424318 DOI: 10.1152/jn.00978.2001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Angiotensin receptors are highly expressed in neonatal spinal cord. To identify their influence on neuronal excitability, we used patch-clamp recordings in spinal cord slices to assess responses of neonatal rat (5-12 days) ventral horn neurons to bath-applied angiotensin II (ANG II; 1 microM). In 14/34 identified motoneurons tested under current clamp, ANG II induced a slowly rising and prolonged membrane depolarization, blockable with Losartan (n = 5) and (Sar(1), Val(5), Ala(8))-ANG II (Saralasin, n = 4) but not PD123319 (1 microM each; n = 4). Under voltage clamp (V(H) -65 mV), 7/22 motoneurons displayed an ANG-II-induced tetrodotoxin-resistant inward current (-128 +/- 31 pA) with a similar time course, an associated reduction in membrane conductance and net current reversal at -98.8 +/- 3.9 mV. Losartan-sensitive ANG II responses were also evoked in 27/78 tested ventral horn "interneurons." By contrast with motoneurons, their ANG-II-induced inward current was smaller (-39.9 +/- 5.2 pA) and analysis of their I-V plots revealed three patterns. In eight cells, membrane conductance decreased with net inward current reversing at -103.8 +/- 4.1 mV. In seven cells, membrane conductance increased with net current reversing at -37.9 +/- 3.6 mV. In 12 cells, I-V lines remained parallel with no reversal within the current range tested. Intracellular dialysis with GTP-gamma-S significantly prolonged the ANG II effect in seven responsive interneurons and GDP-beta-S significantly reduced the ANG II response in four other cells. Peak inward currents were significantly reduced in all 13 responding neurons recorded in slices incubated in pertussis toxin (5 microgram/ml) for 12-18 h or in 12 neurons perfused with N-ethylmaleimide. Of 29 interneurons sensitive to pertussis toxin or N-ethylmaleimide treatment, 9 cells displayed a decrease in membrane conductance that reversed at -101.3 +/- 3.8 mV. In eight cells, membrane conductance increased and reversed at -38.7 +/- 3.4 mV. In 12 cells, the I-V lines remained parallel with no reversal within the current range tested, suggesting that both conductances are modulated by pertussis toxin-sensitive G proteins. These observations reveal a direct, G-protein-mediated depolarizing action of ANG II on neonatal rat ventral horn neurons. They also imply involvement of two distinct conductances that are differentially distributed among different cell types.
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Affiliation(s)
- Murat Oz
- National Institute on Drug Abuse, Intramural Research Program, Baltimore, Maryland 21224, USA.
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30
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Karst H, Nair S, Velzing E, Rumpff-van Essen L, Slagter E, Shinnick-Gallagher P, Joëls M. Glucocorticoids alter calcium conductances and calcium channel subunit expression in basolateral amygdala neurons. Eur J Neurosci 2002; 16:1083-9. [PMID: 12383237 DOI: 10.1046/j.1460-9568.2002.02172.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glucocorticoid hormones, which are released in high amounts after stress, enter the brain where they bind to intracellular receptors that are abundant in limbic areas, in particular the hippocampus and amygdala nuclei. Behavioural studies indicate that glucocorticoids modulate learning and memory processes via receptors in the hippocampus and amygdala. So far, the effects of glucocorticoids on amygdala neurons have not been investigated at the cellular and molecular level. We report here that in vitro application of glucocorticoids for 20 min increases 1-4 h later the amplitude of sustained, high-voltage-activated calcium currents in principal neurons of the basolateral amygdala. In contrast, the transient, low-voltage-activated currents were decreased. We examined whether these functional changes in calcium conductance were accompanied by transcriptional regulation of calcium channel subunits. Analysis of the RNA - collected after recording and then linearly amplified - revealed that glucocorticoid-mediated increases in sustained calcium currents are associated with a parallel shift in the relative expression of the alpha1 subunit constituting the pore of the sustained, high-voltage-activated (L-type) calcium channel. These data indicate that glucocorticoids, probably by selectively targeting genes encoding calcium channel subunits, largely alter the calcium influx into basolateral amygdala neurons. These actions could modify amygdala network function and thus contribute to the behavioural effects exerted by the stress hormones via the basolateral amygdala.
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MESH Headings
- Amygdala/drug effects
- Amygdala/metabolism
- Androstanols/pharmacology
- Animals
- Calcium/metabolism
- Calcium Channels/drug effects
- Calcium Channels/genetics
- Calcium Channels/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium Channels, P-Type/drug effects
- Calcium Channels, P-Type/genetics
- Calcium Channels, P-Type/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Corticosterone/pharmacology
- Glucocorticoids/metabolism
- Glucocorticoids/pharmacology
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Memory/drug effects
- Memory/physiology
- Memory Disorders/metabolism
- Memory Disorders/physiopathology
- Neurons/drug effects
- Neurons/metabolism
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Glucocorticoid/drug effects
- Receptors, Glucocorticoid/metabolism
- Receptors, N-Methyl-D-Aspartate/genetics
- Stress, Physiological/metabolism
- Stress, Physiological/physiopathology
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Affiliation(s)
- Henk Karst
- Section Neurobiology, Swammerdam Institute for Life Sciences, University of Amsterdam, the Netherlands Department Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, USA
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31
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McDonald AJ, Mascagni F. Immunohistochemical characterization of somatostatin containing interneurons in the rat basolateral amygdala. Brain Res 2002; 943:237-44. [PMID: 12101046 DOI: 10.1016/s0006-8993(02)02650-1] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
There are discrete subpopulations of GABAergic interneurons in the basolateral amygdala (ABL) that contain particular neuropeptides or calcium-binding proteins (calbindin-D28k, parvalbumin (PV), or calretinin). The present study employed a dual-labeling immunofluorescence technique combined with confocal laser scanning microscopy to investigate the neurochemical characteristics of the interneuronal subpopulation containing somatostatin (SOM). The great majority of SOM+ neurons in the ABL exhibited GABA immunoreactivity (66-82% depending on the nucleus). These SOM+ neurons constituted 11-18% of the GABA+ population. There was also extensive colocalization of SOM with calbindin (CB) in all nuclei of the ABL, but no colocalization of SOM with parvalbumin, calretinin, or vasoactive intestinal polypeptide. In the basolateral nucleus more than 90% of SOM+ neurons also exhibited CB immunoreactivity, whereas in the lateral nucleus about two-thirds of SOM+ neurons contained significant levels of CB. These SOM/CB neurons constituted about one quarter of the CB+ population in the basolateral nucleus and about one third of the CB+ population in the lateral nucleus. These results, in conjunction with the findings of previous studies, indicate that there are at least three major subpopulations of GABAergic interneurons in the ABL: (i) SOM+ neurons (most of which also contain CB and/or neuropeptide Y); (ii) PV+ neurons (most of which also contain CB); and (iii) CR+ neurons (most of which also contain vasoactive intestinal polypeptide).
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Affiliation(s)
- Alexander J McDonald
- Department of Cell Biology and Neuroscience, University of South Carolina School of Medicine, Bldg 1, Columbia, SC 29208, USA.
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32
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Gao XB, van den Pol AN. Melanin-concentrating hormone depresses L-, N-, and P/Q-type voltage-dependent calcium channels in rat lateral hypothalamic neurons. J Physiol 2002; 542:273-86. [PMID: 12096069 PMCID: PMC2290404 DOI: 10.1113/jphysiol.2002.019372] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Melanin-concentrating hormone (MCH), a cyclic 19-amino-acid peptide, is synthesized exclusively by neurons in the lateral hypothalamic (LH) area. It is involved in a number of brain functions and recently has raised interest because of its role in energy homeostasis. MCH axons and receptors are found throughout the brain. Previous reports set the foundation for understanding the cellular actions of MCH by using non-neuronal cells transfected with the MCH receptor gene; these cells exhibited an increase in cytoplasmic calcium in response to MCH, suggesting an excitatory action for the peptide. In the study presented here, we have used whole-cell recording in 117 neurons from LH cultures and brain slices to examine the actions of MCH. MCH decreased the amplitude of voltage-dependent calcium currents in almost all tested neurons. The inhibition desensitized rapidly (18 s to half maximum at 100 nM concentration) and was dose-dependent (IC(50) = 7.8 nM) when activated with a pulse from -80 mV to 0 mV. A priori activation of G-proteins with GTPgammaS completely eliminated the MCH-induced effect at low MCH concentrations and reduced the MCH-induced effect at high MCH concentrations. Inhibition of G-proteins with pertussis toxin (PTX) blocked the MCH-induced inhibitory effect at high MCH concentrations. Pre-pulse depolarization resulted in an attenuation of the MCH-induced inhibition of calcium currents in most neurons. These data suggest that MCH exerts an inhibitory effect on calcium currents via PTX-sensitive G-protein pathways, probably the G(i)/G(o) pathway, in LH neurons. L-, N- and P/Q-type calcium channels were identified in LH neurons, with L- and N-type channels accounting for most of the voltage-activated current (about 40 % each); MCH attenuated each of the three types (mean 50 % depression), with the greatest inhibition found for N-type currents. In contrast to previous data on non-neuronal cells showing an MHC-evoked increase in calcium, our data suggest that the reverse occurs in LH neurons. The attenuation of calcium currents is consistent with an inhibitory action for the peptide in neurons.
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Affiliation(s)
- Xiao-Bing Gao
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06520, USA
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33
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Vilchis C, Bargas J, Pérez-Roselló T, Salgado H, Galarraga E. Somatostatin modulates Ca2+ currents in neostriatal neurons. Neuroscience 2002; 109:555-67. [PMID: 11823066 DOI: 10.1016/s0306-4522(01)00503-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Somatostatin is synthesized and released by aspiny interneurons of the neostriatum. This work investigates the actions of somatostatin on rat neostriatal neurons of medium size (ca. 6 pF). Somatostatin (1 microM) reduces both calcium action potentials (20 mM tetraethylammonium) by ca. 24% and calcium currents by ca. 35%, in all cells tested. This action was produced in the presence of tetrodotoxin and in dissociated cells and was blocked by cyclo(-7-aminoheptanoyl-phe-d-try-lys-O-benzyl-thr) acetate (CPP-1), a somatostatin receptor antagonist. Except for nitrendipine (5 microM), several calcium channel antagonists, 1 microM omega-conotoxin GVIA, 400 nM omega-agatoxin TK, and 1 microM omega-conotoxin MVIIC, partially occluded somatostatin action. According to the calcium channel types known to be blocked by these antagonists, P/Q-type channels appeared to be the channels mainly modulated by somatostatin, followed by N-type channels. Since these channel types generate the afterhyperpolarizing potential in spiny neurons, we investigated the action of somatostatin on this event. Somatostatin reduces the amplitude of the afterhyperpolarizing potential by ca. 39%. This action is occluded by omega-agatoxin TK and omega-conotoxin MVIIC but not by omega-conotoxin GVIA or nicardipine. Thus, the action of somatostatin on the afterhyperpolarizing potential is mainly mediated by P/Q-type calcium channels. The block of the slow afterhyperpolarizing potential made most neurons exhibit an irregular firing mode, suggesting that ion currents other than calcium may also be affected by somatostatin. We conclude that somatostatin exerts a direct postsynaptic effect on neostriatal neurons via the activation of somatostatin receptors. This action affects non-L-type calcium channels and therefore modifies the afterhyperpolarizing potential and the firing pattern. It is proposed that somatostatin and its analogues may have profound effects on the motor functions controlled by the basal ganglia.
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Affiliation(s)
- C Vilchis
- Departamento de Biofísica, Instituto de Fisiología Celular, UNAM, PO Box 70-253, D.F. 04510, México City, Mexico
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34
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Melyan Z, Wheal HV, Lancaster B. Metabotropic-mediated kainate receptor regulation of IsAHP and excitability in pyramidal cells. Neuron 2002; 34:107-14. [PMID: 11931745 DOI: 10.1016/s0896-6273(02)00624-4] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Kainate receptors (KARs) on CA1 pyramidal cells make no detectable contribution to EPSCs. We report that these receptors have a metabotropic function, as shown previously for CA1 interneurons. Brief kainate exposure caused long-lasting inhibition of a postspike potassium current (I(sAHP)) in CA1 pyramidal cells. The pharmacological profile was independent of AMPA receptors or the GluR5 subunit, indicating a possible role for the GluR6 subunit. KAR inhibition of I(sAHP) did not require ionotropic action or network activity, but was blocked by the inhibitor of pertussis toxin-sensitive G proteins, N-ethylmaleimide (NEM), or the PKC inhibitor calphostin C. These data suggest how KARs, putatively containing GluR6, directly increase excitability of CA1 pyramidal cells and help explain the propensity for seizure activity following KAR activation.
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Affiliation(s)
- Zare Melyan
- Centre for Neuroscience, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, United Kingdom
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35
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Lin CH, Huang YC, Tsai JJ, Gean PW. Modulation of voltage-dependent calcium currents by serotonin in acutely isolated rat amygdala neurons. Synapse 2001; 41:351-9. [PMID: 11494406 DOI: 10.1002/syn.1092] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The modulation of voltage-dependent calcium currents (I(Ca)) by serotonin (5-HT) was studied in rat acutely dissociated amygdala neurons using whole-cell patch-clamp recording techniques. 5-HT inhibited I(Ca) in a concentration-dependent manner with a ED50 of approximately 1 microM and a maximal inhibition of approximately 50%. The inhibition was mimicked by the selective 5-HT1A agonist 8-hydroxy-dipropylaminotetralin (8-OH-DPAT) and was reduced by the 5-HT1A antagonist NAN-190, indicating its mediation by 5-HT1A receptors. Pretreatment of neurons with the alkylating agent N-ethylmaleimide (NEM) or pertussis toxin (PTX) markedly reduced the action of 5-HT. The modulation was partially reversed by strong depolarization and was not seen in cell-attached patches when the agonist was applied outside the recorded patch, suggesting a membrane-delimited, G-protein-mediated signaling pathway. Nimodipine (1 microM) reduced the I(Ca) by approximately 30% without reducing inhibition of current by 5-HT significantly, ruling out L-type channels as the target of modulation. 5-HT-mediated inhibition after exposure to omega-conotoxin-GVIA (omega-CgTX, 1 microM) or omega-agatoxin-IV (omega-AgTX, 200 nM), which blocked 26% and 21% of the total I(Ca), respectively, was significantly decreased, suggesting involvement of the N- and P/Q-type channels. In the combined presence of omega-CgTX and omega-AgTX, 5-HT still caused a small but significant reduction of I(Ca), suggesting a possible involvement of R-type channels. Stimulation of beta-adrenergic receptor with isoproterenol (Iso) or activation of adenylyl cyclase with forskolin resulted in an enhancement of I(Ca). 5-HT caused the same degree of inhibition with or without Iso or forskolin pretreatment. On the other hand, application of 8-OH-DPAT inhibited I(Ca) and blocked Iso- and Sp-cAMPS-induced enhancement. These results provide the first evidence showing a dominant effect of 5-HT-mediated inhibition over Iso-mediated enhancement of I(Ca).
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Affiliation(s)
- C H Lin
- Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan 701
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36
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Ho W, Jung BP, Zhang G, Eubanks JH. Somatostatin type 2 receptor expression in the rat hippocampus following cerebral ischemia. Neuroreport 2001; 12:2105-9. [PMID: 11447316 DOI: 10.1097/00001756-200107200-00013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We examined how transient cerebral ischemia affects the mRNA expression, and the immunoreactive distribution, of the somatostatin type 2 (sst2) receptor in the adult rat hippocampus. Following reperfusion, sst2 mRNA levels increased significantly in the CA1 region by 3 h, and were also increased in the CA3 and CA4/hilus subfields at 6 and 12 h. At 24 h, however, sst2 receptor mRNA levels returned to baseline throughout the hippocampus. At the protein level, we found the regional immunoreactivity of the sst2a receptor was maintained, or slightly elevated, throughout the hippocampus at 6 h, but not different from control at 24 h. These results suggest that sst2 receptors maintain their normal distribution and prevalence in the post-ischemic hippocampus before the deterioration of the vulnerable CA1 neurons. Thus, they represent attractive targets for neuroprotective interventions.
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Affiliation(s)
- W Ho
- Division of Cellular and Molecular Biology, Suite MC 11-412, Toronto Western Research Institute, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada
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37
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Meis S, Pape HC. Control of glutamate and GABA release by nociceptin/orphanin FQ in the rat lateral amygdala. J Physiol 2001; 532:701-12. [PMID: 11313440 PMCID: PMC2278570 DOI: 10.1111/j.1469-7793.2001.0701e.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2000] [Accepted: 01/08/2001] [Indexed: 11/26/2022] Open
Abstract
The actions of the heptadecapeptide termed nociceptin or orphanin FQ (N/OFQ) and the recently discovered putative precursor product nocistatin were examined on synaptic transmission in putative projection cells of the rat lateral amygdala using the whole-cell patch-clamp technique. N/OFQ decreased evoked non-NMDA receptor-mediated excitatory postsynaptic current (EPSC) amplitudes in a concentration-dependent manner, with a half-maximal inhibitory effect elicited by 21.8 +/- 7.5 nM and a Hill coefficient of 0.8 +/- 0.2 (n = 22). Responses were maximally suppressed to 70.3 +/- 1.7 % of the control value. The effect of N/OFQ was prevented by 1 microM [Phe1[psi](CH2-NH)Gly2]NC(1-13)NH2 (Phe[psi]N/OFQ), a substance known as an antagonist/partial agonist of the ORL receptor. GABA(A) receptor-mediated inhibitory postsynaptic currents (IPSCs) elicited through intra-amygdaloid stimulation were reduced to 48.0 +/- 6.8 % by 1 microM N/OFQ (n = 5). Nocistatin had no measurable effect on evoked synaptic currents or membrane properties of recorded neurons. N/OFQ reduced the frequency of spontaneous miniature EPSCs and IPSCs to 74.0 +/- 2.6 % and 84.4 +/- 1.1 %, respectively, without affecting the amplitudes. The present findings indicate that N/OFQ, but not nocistatin, inhibits the release of glutamate and GABA in the lateral amygdala, presumably by acting on presynaptic release sites. These mechanisms may add to the role of N/OFQ in reducing stress vulnerability as recently proposed on the basis of behavioural and genetic approaches.
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Affiliation(s)
- S Meis
- Institut für Physiologie, Otto-von-Guericke-Universität, D-39120 Magdeburg, Germany
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38
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Abstract
Somatostatin, and the recently discovered neuropeptide cortistatin, exert their physiological actions via a family of six G protein-coupled receptors (sst1, sst2A, sst2B, sst3, sst4, sst5). Following the cloning of somatostatin receptors significant advances have been made in our understanding of their molecular, pharmacological and signaling properties although much progress remains to be done to define their physiological role in vivo. In this review, the present knowledge regarding neuroanatomical localization, signal transduction pathways, desensitization and internalization properties of somatostatin receptors is summarized. Evidence that somatostatin receptors can form homo- and heterodimers and can physically interact with members of the SSTRIP/Shank/ProSAP1/CortBP1 family is also discussed.
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Affiliation(s)
- Z Csaba
- Inserm U549, IFR Broca-Sainte Anne, Centre Paul Broca, Paris, France
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39
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McCool BA, Farroni JS. A1 adenosine receptors inhibit multiple voltage-gated Ca2+ channel subtypes in acutely isolated rat basolateral amygdala neurons. Br J Pharmacol 2001; 132:879-88. [PMID: 11181429 PMCID: PMC1572624 DOI: 10.1038/sj.bjp.0703884] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The anticonvulsant properties of 2-chloroadenosine (CADO) in the basolateral amygdala rely on the activation of adenosine-specific heptahelical receptors. We have utilized whole-cell voltage-clamp electrophysiology to examine the modulatory effects of CADO and other adenosine receptor agonists on voltage-gated calcium channels in dissociated basolateral amygdala neurons. 2. CADO, adenosine, and the A1 subtype-selective agonists N6-(L-2-Phenylisopropyl)adenosine (R-PIA) and 2-chloro-N6-cyclopentyladenosine (CCPA) reversibly modulated whole cell Ba2+ currents in a concentration-dependent fashion. CADO inhibition of barium currents was also sensitive to the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). 3. The A2A-selective agonist 4-[2-[[6-Amino-9-(N-ethyl-beta-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid (CGS21680) was without effect. 4. CADO inhibition was predominantly voltage-dependent and sensitive to the sulphydryl-modifying reagent N:-ethylmaleimide, implicating a membrane-delimited, G(i/o)-coupled signal transduction pathway in the channel regulation. 5. Using Ca2+ channel subtype-selective antagonists, CADO inhibition appeared to target multiple channel subtypes, with the inhibition of omega-conotoxin GVIA-sensitive calcium channels being more prominent. 6. Our results indicate that the anti-convulsant effects CADO in the basolateral amygdala may be mediated, in part, by the A1 receptor-dependent inhibition of voltage gated calcium channels.
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Affiliation(s)
- B A McCool
- Department of Medical Pharmacology and Toxicology, The Texas A&M University System Health Science Center, College Station, Texas, TX 77843, USA.
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40
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Abstract
This review discusses the expression and cellular localization of the neuropeptide somatostatin (SRIF) and one of the SRIF subtype (sst) receptors, sst(2A) in the mammalian retina. SRIF immunoreactivity is predominantly localized to a sparse population of amacrine and displaced amacrine cells in the ganglion cell layer in several mammalian retinas including the rat, rabbit, cat, and primate. These cells, characterized by multiple processes, form a sparse network in the inner plexiform layer (IPL) in all retinal regions. Very few processes are also in the outer plexiform layer. In contrast to the predominant distribution of SRIF processes to the IPL, there is a widespread distribution of sst(2A) immunoreactivity to both the inner and outer retina in all mammalian retinas studied to date. In rabbit retina, sst(2A) immunoreactivity is predominant in rod bipolar cells and in sparse wide-field amacrine cells. In the rat retina, sst(2A) immunoreactivity is localized to several neuronal cell types-cone photoreceptors, horizontal cells, rod and cone bipolar cells, and amacrine cells. Reverse-transcriptase-polymerase chain reaction analysis found that sst(2A) mRNA is expressed in the rat retina, while sst(2B) mRNA is not detected. Finally, in the primate retina sst(2) immunoreactivity is predominant in cone photoreceptors, with additional immunostained cell bodies and processes in the inner retina. These findings indicate that SRIF may modulate several neuronal cell types in the retina, and that it has a broad influence on both scotopic and photopic visual pathways.
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Affiliation(s)
- J Johnson
- Department of Ophthalmology, UCSF, San Francisco, California, USA
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41
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Selmer I, Schindler M, Allen JP, Humphrey PP, Emson PC. Advances in understanding neuronal somatostatin receptors. REGULATORY PEPTIDES 2000; 90:1-18. [PMID: 10828487 DOI: 10.1016/s0167-0115(00)00108-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It has long been considered that somatostatin acts as a neuromodulator in the mammalian central nervous system but its precise physiological roles remain elusive. Early studies to identify somatostatin-binding sites revealed a widespread heterogeneous pattern, especially in the CNS. More recently, a family of somatostatin receptors have been identified, of which five genes (sst(1-5)) have been cloned. In this review, we discuss current data describing the localisation of the five receptor types. Recent progress in understanding their function has been made using high-affinity, selective receptor ligands and transgenic animal technology. Finally, the therapeutic potential for somatostatin receptor-selective compounds as analgesics is considered.
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Affiliation(s)
- I Selmer
- Department of Neurobiology, The Babraham Institute, Babraham Hall, CB2 4EF, Cambridge, UK.
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42
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Cui LN, Coderre E, Renaud LP. GABA(B) presynaptically modulates suprachiasmatic input to hypothalamic paraventricular magnocellular neurons. Am J Physiol Regul Integr Comp Physiol 2000; 278:R1210-6. [PMID: 10801289 DOI: 10.1152/ajpregu.2000.278.5.r1210] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study used whole cell patch clamp recordings in rat hypothalamic slice preparations to evaluate the effects of GABA(B) receptor activation on GABA(A)-mediated inhibitory postsynaptic currents (IPSCs) in paraventricular nucleus magnocellular neurons evoked by electrical stimulation in the suprachiasmatic nucleus (SCN). Baclofen induced a dose-dependent (1-10 microM) and reversible reduction in SCN-evoked IPSC amplitude (11/11 cells), blockable with 2-hydroxysaclofen (300 microM; 3/3 cells). IPSCs displayed paired-pulse depression (PPD), attenuated by both baclofen and 2-hydroxysaclofen, but neither altered resting membrane conductances or IPSC time constants of decay. Baclofen induced a significant dose-dependent (1-100 microM) reduction in frequency, but not amplitude, of spontaneous IPSCs and miniature IPSCs, reversible with 2-hydroxysaclofen pretreatment. Baclofen effects and PPD persisted in slices pretreated with pertussis toxin (PTX) and N-ethylmaleimide, implying that these GABA(B) receptors are coupled to PTX-insensitive G proteins. Responses were unaltered by barium (2 mM) or nimodipine, ruling out involvement of K(+) channels and L-type Ca(2+) channels. Thus pre- and postsynaptic GABA(B) and GABA(A) receptors participate in SCN entrainment of paraventricular neurosecretory neurons.
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Affiliation(s)
- L N Cui
- Laboratory of Neurosciences, Loeb Health Research Institute, Ottawa Hospital Civic Site; and University of Ottawa, Ottawa, Ontario, Canada K1Y 4E9
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McCool BA, Botting SK. Characterization of strychnine-sensitive glycine receptors in acutely isolated adult rat basolateral amygdala neurons. Brain Res 2000; 859:341-51. [PMID: 10719083 DOI: 10.1016/s0006-8993(00)02026-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Large concentrations of the beta-amino acid, taurine, can be found in many forebrain areas such as the basolateral amygdala, a portion of the limbic forebrain intimately associated with the regulation of fear/anxiety-like behaviors. In addition to its cytoprotective and osmoregulatory roles, taurine may also serve as an agonist at GABA(A)- and strychnine-sensitive glycine receptors. In this latter context, the present study demonstrates that application of taurine to acutely isolated neurons from the basolateral amygdala of adult rats causes significant alterations in resting membrane current, as measured by whole-cell patch clamp electrophysiology. Using standard pharmacological approaches, we find that currents gated by concentrations of taurine </=3 mM are predominantly mediated by strychnine-sensitive receptors. Furthermore, these strychnine-sensitive receptors are shown to be pharmacologically and biophysically similar to 'classic' strychnine-sensitive, chloride-conducting glycine receptors expressed in brainstem and spinal cord. While amygdala glycine receptors can be distinguished from GABA(A) receptors expressed by the same neurons, these two chloride channels are functionally expressed at comparable levels. Given that a number of clinically relevant compounds are associated with the regulation of GABA(A) receptors in this brain region, the presence of both strychnine-sensitive glycine receptors and their agonist, taurine, in the basolateral amygdala may suggest an important role for these receptors in the limbic forebrain of adult rats.
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Affiliation(s)
- B A McCool
- Department of Medical Pharmacology, Texas A&M University System Health Science Center, 368 Reynolds Building, College Station, TX, USA.
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Shapiro MS, Roche JP, Kaftan EJ, Cruzblanca H, Mackie K, Hille B. Reconstitution of muscarinic modulation of the KCNQ2/KCNQ3 K(+) channels that underlie the neuronal M current. J Neurosci 2000; 20:1710-21. [PMID: 10684873 PMCID: PMC6772928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Channels from KCNQ2 and KCNQ3 genes have been suggested to underlie the neuronal M-type K(+) current. The M current is modulated by muscarinic agonists via G-proteins and an unidentified diffusible cytoplasmic messenger. Using whole-cell clamp, we studied tsA-201 cells in which cloned KCNQ2/KCNQ3 channels were coexpressed with M(1) muscarinic receptors. Heteromeric KCNQ2/KCNQ3 currents were modulated by the muscarinic agonist oxotremorine-M (oxo-M) in a manner having all of the characteristics of modulation of native M current in sympathetic neurons. Oxo-M also produced obvious intracellular Ca(2+) transients, observed by using indo-1 fluorescence. However, modulation of the current remained strong even when Ca(2+) signals were abolished by the combined use of strong intracellular Ca(2+) buffers, an inhibitor of IP(3) receptors, and thapsigargin to deplete Ca(2+) stores. Muscarinic modulation was not blocked by staurosporine, a broad-spectrum protein kinase inhibitor, arguing against involvement of protein kinases. The modulation was not associated with a shift in the voltage dependence of channel activation. Homomeric KCNQ2 and KCNQ3 channels also expressed well and were modulated individually by oxo-M, suggesting that the motifs for modulation are present on both channel subtypes. Homomeric KCNQ2 and KCNQ3 currents were blocked, respectively, at very low and at high concentrations of tetraethylammonium ion. Finally, when KCNQ2 subunits were overexpressed by intranuclear DNA injection in sympathetic neurons, total M current was fully modulated by the endogenous neuronal muscarinic signaling mechanism. Our data further rule out Ca(2+) as the diffusible messenger. The reconstitution of muscarinic modulation of the M current that uses cloned components should facilitate the elucidation of the muscarinic signaling mechanism.
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Affiliation(s)
- M S Shapiro
- Department of Physiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Song J, Jang YY, Shin YK, Lee C, Chung S. N-Ethylmaleimide modulation of tetrodotoxin-sensitive and tetrodotoxin-resistant sodium channels in rat dorsal root ganglion neurons. Brain Res 2000; 855:267-73. [PMID: 10677599 DOI: 10.1016/s0006-8993(99)02405-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The effects of N-ethylmaleimide (NEM), an alkylating reagent to protein sulfhydryl groups, on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium channels in rat dorsal root ganglion (DRG) neurons were studied using the whole cell configuration of patch-clamp technique. When currents were evoked by step depolarizations to 0 mV from a holding potential of -80 mV NEM decreased the amplitude of TTX-S sodium current, but exerted little or no effect on that of TTX-R sodium current. The inhibitory effect of NEM on TTX-S sodium channel was mainly due to the shift of the steady-state inactivation curve in the hyperpolarizing direction. NEM did not affect the voltage-dependence of the activation of TTX-S sodium channel. The steady-state inactivation curve for TTX-R sodium channel was shifted by NEM in the hyperpolarizing direction as that for TTX-S sodium channel. NEM caused a change in the voltage-dependence of the activation of TTX-R sodium channel unlike TTX-S sodium channel. After NEM treatment, the amplitudes of TTX-R sodium currents at test voltages below -10 mV were increased, but those at more positive voltages were not affected. This was explained by the shift in the conductance-voltage curve for TTX-R sodium channels in the hyperpolarizing direction after NEM treatment.
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Affiliation(s)
- J Song
- Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuk-Suk Dong, Dong-Jak Ku, Seoul, South Korea.
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Johnson J, Wu V, Wong H, Walsh JH, Brecha NC. Somatostatin receptor subtype 2A expression in the rat retina. Neuroscience 1999; 94:675-83. [PMID: 10579559 DOI: 10.1016/s0306-4522(99)00170-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Somatostatin is mainly expressed by sparsely occurring amacrine and interplexiform cells in the retina. In this study, we characterized the expression and cellular localization of one of the somatostatin subtype (sst) receptors, sst2A, in the rat retina. The presence of sst2A receptor messenger RNA in retinal extracts was demonstrated by reverse transcription-polymerase chain reaction using specific primers to detect the sst2 receptor and its isoforms, sst2A and sst2B. Specific sst2A receptor immunoreactivity was mainly localized to the plasma membrane of several neuronal cell types. In the outer retina, immunoreactivity was localized to cone photoreceptors, horizontal cells, and rod and cone bipolar cells. Double-label experiments showed the co-localization of sst2A receptor and protein kinase C (alpha and beta), a rod bipolar cell marker, and of sst2A receptor and Calbindin-D28k, a horizontal cell marker. In the inner retina, sst2A receptor immunoreactivity occurred in tyrosine hydroxylase-positive amacrine cells; most were of medium to large size. These findings indicate that somatostatin may act at a distance, in a paracrine manner, on several cell types that express the sst2A receptor, and therefore exert a broad modulatory influence on both scotopic and photopic visual pathways.
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Affiliation(s)
- J Johnson
- Department of Neurobiology, UCLA School of Medicine, Los Angeles, CA 90095-1763, USA
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Zilberter Y, Kaiser KM, Sakmann B. Dendritic GABA release depresses excitatory transmission between layer 2/3 pyramidal and bitufted neurons in rat neocortex. Neuron 1999; 24:979-88. [PMID: 10624960 DOI: 10.1016/s0896-6273(00)81044-2] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
GABAergic, somatostatin-containing bitufted interneurons in layer 2/3 of rat neocortex are excited via glutamatergic excitatory postsynaptic potentials (EPSPs) by pyramidal neurons located in the same cortical layer. Pair recordings showed that short bursts of backpropagating dendritic action potentials (APs) reduced the amplitude of unitary EPSPs. EPSP depression was dependent on a rise in dendritic [Ca2+]. The effect was blocked by the GABA(B) receptor (GABA(B)-R) antagonist CGP55845A and was mimicked by the GABA(B)-R agonist baclofen. As presynaptic GABA(B)-Rs were activated neither by somatostatin nor by GABA released from axon collaterals of the bitufted cell, we conclude that GABA(B)-Rs were activated by a retrograde messenger, most likely GABA, released from the dendrite. Because synaptic depression was prevented by loading bitufted neurons with GDP-beta-S, it is likely to be caused by exocytotic GABA release from dendrites.
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Affiliation(s)
- Y Zilberter
- Abteilung Zellphysiologie, Max-Plank-Institut für Medizinische Forschung, Heidelberg, Federal Republic of Germany.
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Phelan KD. N-ethylmaleimide selectively blocks presynaptic GABA-B autoreceptor but not heteroreceptor-mediated inhibition in adult rat striatal slices. Brain Res 1999; 847:308-13. [PMID: 10575101 DOI: 10.1016/s0006-8993(99)02105-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Intracellular recording techniques were used in slices of adult rat striatum to compare the sensitivity of presynaptic gamma-aminobutyric acid type B (GABA-B) autoreceptor and heteroreceptor-mediated inhibition to the sulfhydryl alkylating agent, N-ethylmaleimide (NEM). NEM (100 microM) alone had no significant effect on resting potential or input resistance and did not consistently effect stimulus-evoked responses. Treatment of slices with NEM for up to 1 h, either in the presence or the absence of the GABA-B receptor-specific agonist, baclofen (BAC; 100 microM), completely blocked the BAC-induced depression of inhibitory, but not excitatory, postsynaptic potentials. This differential sensitivity to NEM alkylation suggests that in the adult rat striatum, the presynaptic GABA-B autoreceptors and heteroreceptors may exhibit distinct receptor-effector coupling mechanisms.
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Affiliation(s)
- K D Phelan
- Department of Anatomy/Slot 510, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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Acosta CG, López HS. delta opioid receptor modulation of several voltage-dependent Ca(2+) currents in rat sensory neurons. J Neurosci 1999; 19:8337-48. [PMID: 10493735 PMCID: PMC6783030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Abstract
Endogenous enkephalins and delta opiates affect sensory function and pain sensation by inhibiting synaptic transmission in sensory circuits via delta opioid receptors (DORs). DORs have long been suspected of mediating these effects by modulating voltage-dependent Ca(2+) entry in primary sensory neurons. However, not only has this hypothesis never been validated in these cells, but in fact several previous studies have only turned up negative results. By using whole-cell current recordings, we show that the delta enkephalin analog [D-Ala(2), D-Leu(5)]-enkephalin (DADLE) inhibits, via DORs, L-, N-, P-, and Q-high voltage-activated Ca(2+) channel currents in cultured rat dorsal root ganglion (DRG) neurons. The percentage of responding cells was remarkably high (75%) within a novel subpopulation of substance P-containing neurons compared with the other cells (18-35%). DADLE (1 microM) inhibited 32% of the total barium current through calcium channels (I(Ba)). A delta (naltrindole, 1 microM), but not a mu (beta-funaltrexamine, 5 microM), antagonist prevented the DADLE response, whereas a DOR-2 subtype (deltorphin-II, 100 nM), but not a DOR-1 (DPDPE, 1 microM), agonist mimicked the response. L-, N-, P-, and Q-type currents contributed, on average, 18, 48, 14, and 16% to the total I(Ba) and 19, 50, 26, and 20% to the DADLE-sensitive current, respectively. The drug-insensitive R-type current component was not affected by the agonist. This work represents the first demonstration that DORs modulate Ca(2+) entry in sensory neurons and suggests that delta opioids could affect diverse Ca(2+)-dependent processes linked to Ca(2+) influx through different high-voltage-activated channel types.
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Affiliation(s)
- C G Acosta
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, Consejo Nacional de Investigaciones Científicas y Técnicas, 5000 Córdoba, Argentina
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Abstract
Somatostatin (SST), a regulatory peptide, is produced by neuroendocrine, inflammatory, and immune cells in response to ions, nutrients, neuropeptides, neurotransmitters, thyroid and steroid hormones, growth factors, and cytokines. The peptide is released in large amounts from storage pools of secretory cells, or in small amounts from activated immune and inflammatory cells, and acts as an endogenous inhibitory regulator of the secretory and proliferative responses of target cells that are widely distributed in the brain and periphery. These actions are mediated by a family of seven transmembrane (TM) domain G-protein-coupled receptors that comprise five distinct subtypes (termed SSTR1-5) that are endoded by separate genes segregated on different chromosomes. The five receptor subtypes bind the natural SST peptides, SST-14 and SST-28, with low nanomolar affinity. Short synthetic octapeptide and hexapeptide analogs bind well to only three of the subtypes, 2, 3, and 5. Selective nonpeptide agonists with nanomolar affinity have been developed for four of the subtypes (SSTR1, 2, 3, and 4) and putative peptide antagonists for SSTR2 and SSTR5 have been identified. The ligand binding domain for SST ligands is made up of residues in TMs III-VII with a potential contribution by the second extracellular loop. SSTRs are widely expressed in many tissues, frequently as multiple subtypes that coexist in the same cell. The five receptors share common signaling pathways such as the inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G-protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K(+) channels (SSTR2, 3, 4, 5), to voltage-dependent Ca(2+) channels (SSTR1, 2), a Na(+)/H(+) exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, 2), phospholipase C (SSTR2, 5), and phospholipase A(2) (SSTR4). SSTRs block cell secretion by inhibiting intracellular cAMP and Ca(2+) and by a receptor-linked distal effect on exocytosis. Four of the receptors (SSTR1, 2, 4, and 5) induce cell cycle arrest via PTP-dependent modulation of MAPK, associated with induction of the retinoblastoma tumor suppressor protein and p21. In contrast, SSTR3 uniquely triggers PTP-dependent apoptosis accompanied by activation of p53 and the pro-apoptotic protein Bax. SSTR1, 2, 3, and 5 display acute desensitization of adenylyl cyclase coupling. Four of the subtypes (SSTR2, 3, 4, and 5) undergo rapid agonist-dependent endocytosis. SSTR1 fails to be internalized but is instead upregulated at the membrane in response to continued agonist exposure. Among the wide spectrum of SST effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2).
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Affiliation(s)
- Y C Patel
- Department of Medicine, Royal Victoria Hospital, Montreal, Quebec, H3A 1A1, Canada
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