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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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Molecular and Cellular Mechanisms Underlying Somatostatin-Based Signaling in Two Model Neural Networks, the Retina and the Hippocampus. Int J Mol Sci 2019; 20:ijms20102506. [PMID: 31117258 PMCID: PMC6566141 DOI: 10.3390/ijms20102506] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/16/2019] [Accepted: 05/20/2019] [Indexed: 02/06/2023] Open
Abstract
Neural inhibition plays a key role in determining the specific computational tasks of different brain circuitries. This functional "braking" activity is provided by inhibitory interneurons that use different neurochemicals for signaling. One of these substances, somatostatin, is found in several neural networks, raising questions about the significance of its widespread occurrence and usage. Here, we address this issue by analyzing the somatostatinergic system in two regions of the central nervous system: the retina and the hippocampus. By comparing the available information on these structures, we identify common motifs in the action of somatostatin that may explain its involvement in such diverse circuitries. The emerging concept is that somatostatin-based signaling, through conserved molecular and cellular mechanisms, allows neural networks to operate correctly.
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Dubovy SR, Fernandez MP, Echegaray JJ, Block NL, Unoki N, Perez R, Vidaurre I, Lee RK, Nadji M, Schally AV. Expression of hypothalamic neurohormones and their receptors in the human eye. Oncotarget 2017; 8:66796-66814. [PMID: 28977997 PMCID: PMC5620137 DOI: 10.18632/oncotarget.18358] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 05/20/2017] [Indexed: 12/27/2022] Open
Abstract
Extrapituitary roles for hypothalamic neurohormones have recently become apparent and clinically relevant, based on the use of synthetic peptide analogs for the treatment of multiple conditions including cancers, pulmonary edema and myocardial infarction. In the eye, it has been suggested that some of these hormones and their receptors may be present in the ciliary body, iris, trabecular meshwork and retina, but their physiological role has yet to be elucidated. Our study intends to comprehensively demonstrate the expression of some hypothalamic neuroendocrine hormones and their receptors within different retinal and extraretinal structures of the human eye. Immunofluorescence, Western blot analysis, and RT-PCR were used to evaluate the qualitative and quantitative expression of Luteinizing Hormone Releasing Hormone (LHRH), Growth Hormone Releasing Hormone (GHRH), Thyrotropin Releasing Hormone (TRH), Gastrin Releasing Peptide (GRP) and Somatostatin as well as their respective receptors (LHRH-R, GHRH-R, TRH-R, GRP-R, SST-R1) in cadaveric human eye tissue and in paraffinized human eye tissue sections. The hypothalamic hormones LHRH, GHRH, TRH, GRP and Somatostatin and their respective receptors (LHRH-R, GHRH-R, TRH-R, GRPR/BB2 and SST-R1), were expressed in the conjunctiva, cornea, trabecular meshwork, ciliary body, lens, retina, and optic nerve.
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Affiliation(s)
- Sander R Dubovy
- Florida Lions Ocular Pathology Laboratory, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA.,Department of Pathology, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Maria P Fernandez
- Florida Lions Ocular Pathology Laboratory, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Jose J Echegaray
- Florida Lions Ocular Pathology Laboratory, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA.,Department of Ophthalmology, University of Puerto Rico School of Medicine, San Juan, PR, USA
| | - Norman L Block
- Department of Pathology, University of Miami, Miller School of Medicine, Miami, Florida, USA.,Divisions of Hematology/Oncology, Endocrinology, Department of Medicine, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Noriyuki Unoki
- Florida Lions Ocular Pathology Laboratory, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Roberto Perez
- Miami Veterans Affairs Medical Center, Miami, Florida, USA.,Divisions of Hematology/Oncology, Endocrinology, Department of Medicine, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | | | - Richard K Lee
- Florida Lions Ocular Pathology Laboratory, Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Mehrdad Nadji
- Department of Pathology, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Andrew V Schally
- Miami Veterans Affairs Medical Center, Miami, Florida, USA.,Department of Pathology, University of Miami, Miller School of Medicine, Miami, Florida, USA.,Divisions of Hematology/Oncology, Endocrinology, Department of Medicine, University of Miami, Miller School of Medicine, Miami, Florida, USA
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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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5
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Parallel Inhibition of Dopamine Amacrine Cells and Intrinsically Photosensitive Retinal Ganglion Cells in a Non-Image-Forming Visual Circuit of the Mouse Retina. J Neurosci 2016; 35:15955-70. [PMID: 26631476 DOI: 10.1523/jneurosci.3382-15.2015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
An inner retinal microcircuit composed of dopamine (DA)-containing amacrine cells and melanopsin-containing, intrinsically photosensitive retinal ganglion cells (M1 ipRGCs) process information about the duration and intensity of light exposures, mediating light adaptation, circadian entrainment, pupillary reflexes, and other aspects of non-image-forming vision. The neural interaction is reciprocal: M1 ipRGCs excite DA amacrine cells, and these, in turn, feed inhibition back onto M1 ipRGCs. We found that the neuropeptide somatostatin [somatotropin release inhibiting factor (SRIF)] also inhibits the intrinsic light response of M1 ipRGCs and postulated that, to tune the bidirectional interaction of M1 ipRGCs and DA amacrine cells, SRIF amacrine cells would provide inhibitory modulation to both cell types. SRIF amacrine cells, DA amacrine cells, and M1 ipRGCs form numerous contacts. DA amacrine cells and M1 ipRGCs express the SRIF receptor subtypes sst(2A) and sst4 respectively. SRIF modulation of the microcircuit was investigated with targeted patch-clamp recordings of DA amacrine cells in TH-RFP mice and M1 ipRGCs in OPN4-EGFP mice. SRIF increases K(+) currents, decreases Ca(2+) currents, and inhibits spike activity in both cell types, actions reproduced by the selective sst(2A) agonist L-054,264 (N-[(1R)-2-[[[(1S*,3R*)-3-(aminomethyl)cyclohexyl]methyl]amino]-1-(1H-indol-3-ylmethyl)-2-oxoethyl]spiro[1H-indene-1,4'-piperidine]-1'-carboxamide) in DA amacrine cells and the selective sst4 agonist L-803,087 (N(2)-[4-(5,7-difluoro-2-phenyl-1H-indol-3-yl)-1-oxobutyl]-L-arginine methyl ester trifluoroacetate) in M1 ipRGCs. These parallel actions of SRIF may serve to counteract the disinhibition of M1 ipRGCs caused by SRIF inhibition of DA amacrine cells. This allows the actions of SRIF on DA amacrine cells to proceed with adjusting retinal DA levels without destabilizing light responses by M1 ipRGCs, which project to non-image-forming targets in the brain.
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6
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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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7
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Gábriel R. Neuropeptides and diabetic retinopathy. Br J Clin Pharmacol 2013; 75:1189-201. [PMID: 23043302 DOI: 10.1111/bcp.12003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 10/02/2012] [Indexed: 12/21/2022] Open
Abstract
Diabetic retinopathy, a common complication of diabetes, develops in 75% of patients with type 1 and 50% of patients with type 2 diabetes, progressing to legal blindness in about 5%. In the recent years, considerable efforts have been put into finding treatments for this condition. It has been discovered that peptidergic mechanisms (neuropeptides and their analogues, activating a diverse array of signal transduction pathways through their multiple receptors) are potentially important for consideration in drug development strategies. A considerable amount of knowledge has been accumulated over the last three decades on human retinal neuropeptides and those elements in the pathomechanisms of diabetic retinopathy which might be related to peptidergic signal transduction. Here, human retinal neuropeptides and their receptors are reviewed, along with the theories relevant to the pathogenesis of diabetic retinopathy both in humans and in experimental models. By collating this information, the curative potential of certain neupeptides and their analogues/antagonists can also be discussed, along with the existing clinical treatments of diabetic retinopathy. The most promising peptidergic pathways for which treatment strategies may be developed at present are stimulation of the somatostatin-related pathway and the pituitary adenylyl cyclase-activating polypeptide-related pathway or inhibition of angiotensinergic mechanisms. These approaches may result in the inhibition of vascular endothelial growth factor production and neuronal apoptosis; therefore, both the optical quality of the image and the processing capability of the neural circuit in the retina may be saved.
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Affiliation(s)
- Robert Gábriel
- Department of Experimental Zoology and Neurobiology, University of Pécs, H-7621, Pécs, Hungary.
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8
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Protective role of somatostatin receptor 2 against retinal degeneration in response to hypoxia. Naunyn Schmiedebergs Arch Pharmacol 2012; 385:481-94. [DOI: 10.1007/s00210-012-0735-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 01/25/2012] [Indexed: 12/20/2022]
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9
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Wu XH, Deng QQ, Jiang SX, Yang XL, Zhong YM. Distribution of somatostatin receptor 5 in mouse and bullfrog retinas. Peptides 2012; 33:291-7. [PMID: 22244811 DOI: 10.1016/j.peptides.2011.12.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 12/30/2011] [Accepted: 12/30/2011] [Indexed: 01/21/2023]
Abstract
Somatostatin (SRIF), as a neuroactive peptide in the CNS, may act as a neuromodulator through activation of five specific receptor subtypes (sst(1)-sst(5)). In this work we conducted a comparative study of the expression of sst(5) in mouse and bullfrog retinas by immunofluorescence double labeling. Basically, the expression profiles of sst(5) in the retinas of the two species were similar. That is, in the inner retina sst(5) was localized to dopaminergic and cholinergic amacrine cells, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) respectively, and cells in the ganglion cell layer, whereas in the outer retina immunostaining for sst(5) was observed in horizontal cells. However, a more widespread, abundant distribution of labeling for sst(5), as compared to mouse retina, was seen in bullfrog retina: strong labeling for sst(5) was diffusely distributed in both outer and inner plexiform layers (OPL and IPL) in the bullfrog retina, but the labeling was only observed in the IPL of the mouse retina. In addition, bullfrog photoreceptors, both rods and cones, but not mouse ones, were labeled by sst(5). In combination with the experiments showing that SRIF-immunoreactivity was mainly found in the inner retina, our results suggest that SRIF, released from SRIF-containing cells in the inner retina, may play a neuromodulatory role in both outer and inner retina mediated by volume transmission via sst(5) in bullfrog retina, while the SRIF action may be largely restricted to the mouse inner retina.
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Affiliation(s)
- Xiao-Hua Wu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
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10
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The retinal pigment epithelium: something more than a constituent of the blood-retinal barrier--implications for the pathogenesis of diabetic retinopathy. J Biomed Biotechnol 2010; 2010:190724. [PMID: 20182540 PMCID: PMC2825554 DOI: 10.1155/2010/190724] [Citation(s) in RCA: 305] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 09/28/2009] [Accepted: 11/16/2009] [Indexed: 12/27/2022] Open
Abstract
The retinal pigment epithelium (RPE) is an specialized epithelium lying in the interface between the neural retina and the choriocapillaris where it forms the outer blood-retinal barrier (BRB). The main functions of the RPE are the following: (1) transport of nutrients, ions, and water, (2) absorption of light and protection against photooxidation, (3) reisomerization of all-trans-retinal into 11-cis-retinal, which is crucial for the visual cycle, (4) phagocytosis of shed photoreceptor membranes, and (5) secretion of essential factors for the structural integrity of the retina. An overview of these functions will be given. Most of the research on the physiopathology of diabetic retinopathy has been focused on the impairment of the neuroretina and the breakdown of the inner BRB. By contrast, the effects of diabetes on the RPE and in particular on its secretory activity have received less attention. In this regard, new therapeutic strategies addressed to modulating RPE impairment are warranted.
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11
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Somatostatin analogues as therapeutics in retinal disease. Pharmacol Ther 2009; 122:324-33. [DOI: 10.1016/j.pharmthera.2009.03.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 03/24/2009] [Indexed: 12/30/2022]
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12
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Ke JB, Zhong YM. Expression of somatostatin receptor subtype 5 in rat retinal amacrine cells. Neuroscience 2007; 144:1025-32. [PMID: 17156933 DOI: 10.1016/j.neuroscience.2006.10.047] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Revised: 10/27/2006] [Accepted: 10/27/2006] [Indexed: 01/01/2023]
Abstract
Somatostatin (SRIF), as a neuroactive peptide in the CNS, exerts its actions via five subtypes of specific receptors (ssts). In this work, the localization of sst(5) was studied immunocytochemically in rat retinal amacrine cells (ACs). Labeling for sst(5) was diffusely distributed throughout the full thickness of the inner plexiform layer (IPL) and formed two distinct fluorescence bands in the distal part of the IPL. Double labeling experiments showed that sst(5) was expressed in GABAergic ACs. It was further shown that labeling for sst(5) was observed in both dopaminergic and cholinergic ACs, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), respectively. The immunostaining appeared mainly on the cell membranes and somatodendritic compartments of these ACs. For the cholinergic ACs, weak sst(5)-immunoreactivity was also observed in the processes terminating in the IPL. In contrast, no sst(5)-immunoreactivity was found in glycinergic AII ACs, stained by parvalbumin (PV). Furthermore, labeling for SRIF was co-localized with sst(5) in both dopaminergic and cholinergic ACs. These results suggest that sst(5) may serve as an autoreceptor or conventional receptor in retinal ACs.
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Affiliation(s)
- J-B Ke
- Institute of Neurobiology and Institutes of Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, PR China
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Ghosh S, Choritz L, Geibel J, Coca-Prados M. Somatostatin modulates PI3K-Akt, eNOS and NHE activity in the ciliary epithelium. Mol Cell Endocrinol 2006; 253:63-75. [PMID: 16764985 DOI: 10.1016/j.mce.2006.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2006] [Revised: 04/10/2006] [Accepted: 05/02/2006] [Indexed: 12/20/2022]
Abstract
Somatostatin (SST) is a biologically active peptide produced in neuroendocrine cells. In the present study, we provide evidence of pro-SST and SST receptor (SSTR1 and 2A) mRNA expression in ocular ciliary epithelium (CE). SST or SST-like immunoreactivity was detected by radioimmunoassay in tissue extract from ciliary processes and in aqueous humor. The distinct immunolabeling of CE with SST and proprotein convertases PC1 and PC2 antibodies suggested a tissue and cell-specific processing of pro-SST. SST (10(-8) to 10(-4)M) added exogenously to the CE, elicited the following effects: (i) a dose-dependent attenuation of Na+/H+-exchanger (NHE) activity; (ii) up to a two-fold increase phosphorylation of p-Akt-Ser473 and of p-eNOS-Ser617, and (iii) lack of response on intracellular cyclic GMP production. LY294002, a PI3K-inhibitor, blocked SST-induced p-Akt-Ser473 and partially p-eNOS-Ser617, however, it did not reverse SST-induced NHE attenuation. Collectively, these results suggested involvement of SST in multiple intracellular signaling pathways in the CE.
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Affiliation(s)
- Sikha Ghosh
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06510, USA
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Bezerra Y, Fuselier JA, Peyman GA, Oner H, Drouant G, Coy DH. STUDY OF INHIBITORY EFFECTS OF AN ANTIANGIOGENIC SOMATOSTATIN-CAMPTOTHECIN CONJUGATE ON LASER-INDUCED CHOROIDAL NEOVASCULARIZATION IN RATS. Retina 2005; 25:345-54. [PMID: 15805913 DOI: 10.1097/00006982-200504000-00015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE To evaluate the ocular toxicity and efficacy of intravitreal camptothecin-somatostatin conjugate (JF-10-81), a somatostatin type 2 receptor-directed, antiangiogenic compound. METHODS Part 1: New Zealand albino rabbits (except for controls) were injected intravitreally with conjugate at various concentrations. Preoperative and postoperative ocular examinations and electroretinography were performed until animals were killed for histology. Part 2: Long-Evans pigmented rats had choroidal neovascularization (CNV) induced by argon laser. One eye per animal was injected with concentration 10M (safe dose), whereas the other eyes were controls and received 30 microL of sterile water at different time intervals after laser application. Fluorescein angiography was performed at various time points to evaluate the lesions and confirm presence of CNV. Animals were euthanized. The eyes were immediately enucleated and prepared for histologic examination. RESULTS Part 1: No clinical changes were seen in groups receiving 10(-8)M, 10(-7)M, 10(-6)M, and 10(-5) M of conjugate. Electroretinography showed decreasing b-wave amplitude in groups receiving 10(-4) M and 10(-3) M; cataracts also developed in these eyes. Part 2: Fluorescein angiography revealed that intravitreal injection of somatostatin conjugate JF-10-81 favorably affected the development of CNV when the treatment was performed at least 1 week after the laser application. These results were statistically significant. Histologic analysis results of eyes treated 2 weeks after laser application also showed significant benefit. CONCLUSIONS Part 1: Camptothecin-somatostatin conjugate injected intravitreally appeared safe at concentrations of 10(-5)M or less. Part 2: Conjugate JF-10-81 at a concentration of 10(-5)M administered intravitreally 1 to 3 weeks after laser demonstrated statistically significant efficacy in the treatment of choroidal neovascularization.
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Affiliation(s)
- Yanno Bezerra
- Department of Ophthalmology, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2699, USA
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15
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Bigiani A, Petrucci C, Ghiaroni V, Dal Monte M, Cozzi A, Kreienkamp HJ, Richter D, Bagnoli P. Functional correlates of somatostatin receptor 2 overexpression in the retina of mice with genetic deletion of somatostatin receptor 1. Brain Res 2005; 1025:177-85. [PMID: 15464758 DOI: 10.1016/j.brainres.2004.07.083] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2004] [Indexed: 01/26/2023]
Abstract
Somatostatin-14 (SRIF) and its receptors (sst(1-5)) are found in the mammalian retina. However, scarce information is available on the role of the somatostatinergic system in retinal physiology. We have recently used gene-knockout technology to gain insights into the function of sst(1) and sst(2) receptors in the mouse retina. The sst(1) receptor localizes to SRIF-containing amacrine cells, whereas the sst(2) receptor localizes to several retinal cell populations including rod bipolar cells (RBCs). Molecular data indicate that, in retinas with deletion of the sst(1) receptor (sst(1) KO), sst(2) receptors become overexpressed in concomitance with an increased level of retinal SRIF. To test whether this up-regulation of sst(2) receptors correlates with altered sst(2) receptor physiology, we studied the effect of sst(2) receptor activation on potassium current (I(K)) in isolated RBCs and glutamate release in retina explants. Both I(K) and glutamate release are known to be negatively modulated by sst(2) receptors in the mammalian retina. We used octreotide, a SRIF analogue, to activate selectively sst(2) receptors. Patch-clamp recordings from isolated RBCs indicated that the sst(2) receptor-mediated inhibition of I(K) was significantly larger in sst(1) KO than in control retinas. In addition, HPLC measurements of glutamate release in sst(1) KO retinal explants demonstrated that the sst(2) receptor-mediated inhibition of K(+)-evoked glutamate release was also significantly larger than in control retinas. As a whole, these findings indicate that the overexpression of sst(2) receptors in sst(1) KO retinas can be correlated to an enhanced function of sst(2) receptors. The level of expression of sst(2) receptors may therefore represent a key step in the regulation of sst(2) receptor-mediated responses, at least in the retina.
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Affiliation(s)
- Albertino Bigiani
- Dipartimento di Scienze Biomediche, Sezione di Fisiologia, Università di Modena e Reggio Emilia via Campi 287, 41100 Modena, Italy.
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16
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D'Angelo I, Brecha NC. Y2 receptor expression and inhibition of voltage-dependent Ca2+ influx into rod bipolar cell terminals. Neuroscience 2004; 125:1039-49. [PMID: 15120863 DOI: 10.1016/j.neuroscience.2003.10.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2003] [Indexed: 11/21/2022]
Abstract
Neuropeptide Y (NPY) is a potent inhibitory neuropeptide expressed by amacrine cells in the rat retina. NPY modulates the release of multiple neurotransmitters in mammalian retina, yet the mechanisms mediating this regulation are not well defined. To further understand the action of NPY in the retina, Y receptor coupling to voltage-dependent Ca(2+) channels was investigated using Ca(2+) imaging with fura-2 AM to measure [Ca(2+)](i) increases in rod bipolar cell terminals. Y receptor expression was studied in rat retinal tissue with reverse transcription-polymerase chain reaction (RT-PCR). NPY inhibited the depolarization-evoked Ca(2+) influx into rod bipolar cell axon terminals and caused a dose-dependent reduction and an average maximal inhibition of 72% at 1 microM, which was reversed upon washout. K(+)-evoked Ca(2+) increases were also inhibited by the selective Y2 receptor agonists, C2-NPY and NPY(13-36), at concentrations of 1 microM, but not by the selective Y1 receptor agonist, [Leu(31)Pro(34)]NPY, selective Y4 receptor agonist, rPP, or the selective Y5 receptor agonist, [d-Trp32]-NPY. Y receptor expression was determined using RT-PCR for all known Y receptor subtypes. Y2 receptor mRNA, as well as Y1, Y4, and Y5 receptor mRNAs, are present in the rat retina. Like the rod bipolar cell, other studies in central neurons have shown that the Y2 receptor is expressed predominantly as a presynaptic receptor and that it modulates transmitter release. Together, these findings suggest that NPY activates presynaptic Y2 receptors to inhibit voltage-dependent Ca(2+) influx into rod bipolar cell terminals, and establishes one mechanism by which NPY may reduce l-glutamate release from the rod bipolar cell synapse.
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Affiliation(s)
- I D'Angelo
- Department of Neurobiology, Box 951763, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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17
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Dal Monte M, Petrucci C, Vasilaki A, Cervia D, Grouselle D, Epelbaum J, Kreienkamp HJ, Richter D, Hoyer D, Bagnoli P. Genetic deletion of somatostatin receptor 1 alters somatostatinergic transmission in the mouse retina. Neuropharmacology 2004; 45:1080-92. [PMID: 14614951 DOI: 10.1016/s0028-3908(03)00296-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In the mammalian retina, sparse amacrine cells contain somatostatin-14 (SRIF) which acts at multiple levels of neuronal circuitry through distinct SRIF receptors (sst(1-5)). Among them, the sst1 receptor has been localised to SRIF-containing amacrine cells in the rat and rabbit retina. Little is known about sst1 receptor localisation and function in the mouse retina. We have addressed this question in the retina of mice with deletion of sst1 receptors (sst1 KO mice). In the retina of wild type (WT) mice, sst1 receptors are localised to SRIF-containing amacrine cells, whereas in the retina of sst1 KO mice, sst1 receptors are absent. sst1 receptor loss causes a significant increase in retinal levels of SRIF, whereas it does not affect SRIF messenger RNA indicating that sst1 receptors play a role in limiting retinal SRIF at the post-transcriptional level. As another consequence of sst1 receptor loss, levels of expression of sst2 receptors are significantly higher than in control retinas. Together, these findings provide the first demonstration of prominent compensatory regulation in the mouse retina as a consequence of a distinct SRIF receptor deletion. The fact that in the absence of the sst1 receptor, retinal SRIF increases in concomitance with an increase in sst2 receptors suggests that SRIF may regulate sst2 receptor expression and that this regulatory process is controlled upstream by the sst1 receptor. This finding can be important in the design of drugs affecting SRIF function, not only in the retina, but also elsewhere in the brain.
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Affiliation(s)
- Massimo Dal Monte
- Dipartimento di Fisiologia e Biochimica, Università di Pisa, via San Zeno 31, 56127 Pisa, Italy
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18
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Casini G, Dal Monte M, Petrucci C, Gambellini G, Grouselle D, Allen JP, Kreienkamp HJ, Richter D, Epelbaum J, Bagnoli P. Altered morphology of rod bipolar cell axonal terminals in the retinas of mice carrying genetic deletion of somatostatin subtype receptor 1 or 2. Eur J Neurosci 2004; 19:43-54. [PMID: 14750962 DOI: 10.1111/j.1460-9568.2004.03081.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Somatostatin (SRIF), similar to other neuropeptides, is likely to influence the morpho-functional characteristics of neurons. We studied possible morphological alterations of mouse retinal neurons following genetic deletion of SRIF subtype receptor 1 [sst1 knockout (KO)] or 2 (sst2 KO). In sst1 KO retinas, axonal terminals of rod bipolar cells (RBCs), identified with protein kinase C immunoreactivity, were 25% larger than in controls. In contrast, in sst2 KO retinas, RBC axonal terminals were significantly smaller (-14%). No major ultrastructural differences were observed between control and KO RBCs. In sst2 KO retinas, SRIF levels decreased by about 35%, while both sst1 receptor mRNA and protein increased by about 170% and 100%, respectively. This compares to previous results reporting an increase of both retinal SRIF and sst2 receptors following sst1 receptor deletion. Together, these findings suggest that, on the one hand, sst1 receptor deletion induces over-expression of sst2 receptors, and vice versa; on the other hand, that an imbalance in sst1 and sst2 receptor expression and/or changes in the levels of retinal SRIF induced by sst1 or sst2 receptor deletion are responsible for the morphological changes in RBC axonal terminals. Similar alterations of RBC terminals were observed in KO retinas at 2 weeks of age (eye opening). In addition, reverse transcription-polymerase chain reaction analysis of the expression of sst2 and sst1 receptors in developing sst1 and sst2 KO retinas, respectively, demonstrated that these receptors are up-regulated at or near eye opening. These findings suggest that the integrity of the somatostatinergic system during development is necessary for proper RBC maturation.
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Affiliation(s)
- Giovanni Casini
- Dipartimento di Scienze Ambientali, Università della Tuscia, 01100 Viterbo, Italy.
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Papadaki T, Tsilimbaris M, Thermos K, Karavellas M, Samonakis D, Papapdakis A, Linardakis M, Kouromalis E, Pallikaris I. The Role of Lanreotide in the Treatment of Choroidal Neovascularization Secondary to Age-Related Macular Degeneration. Retina 2003; 23:800-7. [PMID: 14707831 DOI: 10.1097/00006982-200312000-00010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate the role of somatostatin in the treatment of subfoveal choroidal neovascularization (CNV). METHODS Twenty eyes of 20 patients with CNV were included in the study. Patients were randomly allocated to treatment with lanreotide (10 eyes) or placebo (10 eyes). Patients received one intramuscular injection of lanreotide or placebo every 15 days for a total of 6 months. Follow-up lasted for 6 months for the control group and 12 months for the study group. The changes in visual acuity and fluorescein angiography at 6 months were compared between the two groups. In addition, the changes in the same parameters within the study group, from 6 to 12 months, were studied. RESULTS From baseline to 6 months, the mean visual acuity and surface area of hyperfluorescence remained stable in the study group, while the intensity of hyperfluorescence decreased. After discontinuation of treatment, deterioration of all three parameters was noted in the study group. Statistical analysis, however, failed to reveal any significant difference from baseline. CONCLUSIONS During treatment with lanreotide, a trend for stabilization of visual acuity and intensity of hyperfluorescence was documented in the study group, but it did not reach statistically significant levels. Further randomized, controlled clinical trials with larger samples and longer duration of treatment and follow-up are warranted to evaluate the role of lanreotide in the treatment of age-related CNV.
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Affiliation(s)
- Thekla Papadaki
- Department of Ophthalmology, University of Crete Medical School, Heraklion, Crete, Greece
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Abstract
The peptide somatostatin is one of many neuroactive agents that influence retinal physiology. It is synthesized primarily in a subclass of amacrine cells and believed to function as a neurotransmitter, neuromodulator or trophic factor. The cloning of the somatostatin receptors (sst1-5) in the early nineties provided the appropriate tools for the study of ssts in many tissues, including the retina. In this review, emphasis is given to recent studies that have provided significant information on the functional role of somatostatin in retinal circuitry and the retinal pigment epithelium. The important role of somatostatin in retinal disease therapeutics is also discussed.
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Affiliation(s)
- Kyriaki Thermos
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Laboratory of Pharmacology, Heraclion, Crete 71 110, Greece.
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21
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Grigoryan EN, Vasilaki A, Mastrodimou N, Thermos K. Somatostatin receptor immunoreactivity in the eye of the adult newt (Pleurodeles waltlii Michan). Neurosci Lett 2003; 337:143-6. [PMID: 12536044 DOI: 10.1016/s0304-3940(02)01326-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The neuropeptide somatostatin is found in the retina of many species, yet its role in the visual process remains to be elucidated. The aim of the present study was to examine the expression and cellular localization of somatostatin receptor subtypes (sst; sst(2A), sst(2B) and sst(3)) in the eye of the adult newt Pleurodeles waltlii using immunohistochemistry. sst(2A) immunoreactivity was observed in bipolar cells, in the inner segments of cone photoreceptors, as well as in the region corresponding to connecting cilia of rods. sst(2B) immunoreactivity was not detected. sst(3) immunostaining was localized most intensely in the inner segments of cones, and in cilia of rods. These results suggest that somatostatin acting via sst(2A) and sst(3) receptors may play an important role in retinal physiology of the lower vertebrates.
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Affiliation(s)
- Eleonora N Grigoryan
- Institute of Developmental Biology, Russian Academy of Sciences, Moscow 117808, Russia
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22
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D'Angelo I, Oh SJ, Chun MH, Brecha NC. Localization of neuropeptide Y1 receptor immunoreactivity in the rat retina and the synaptic connectivity of Y1 immunoreactive cells. J Comp Neurol 2002; 454:373-82. [PMID: 12455004 PMCID: PMC3696015 DOI: 10.1002/cne.10423] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Neuropeptide Y (NPY), an inhibitory neuropeptide expressed by a moderately dense population of wide-field amacrine cells in the rat retina, acts through multiple (Y1-y6) G-protein-coupled receptors. This study determined the cellular localization of Y1 receptors and the synaptic connectivity of Y1 processes in the inner plexiform layer (IPL) of the rat retina. Specific Y1 immunoreactivity was localized to horizontal cell bodies in the distal inner nuclear layer and their processes in the outer plexiform layer. Immunoreactivity was also prominent in cell processes located in strata 2 and 4, and puncta in strata 4 and 5 of the IPL. Double-label immunohistochemical experiments with calbindin, a horizontal cell marker, confirmed Y1 immunostaining in all horizontal cells. Double-label immunohistochemical experiments, using antibodies to choline acetyltransferase and vesicular acetylcholine transporter to label cholinergic amacrine cell processes, demonstrated that Y1 immunoreactivity in strata 2 and 4 of the IPL was localized to cholinergic amacrine cell processes. Electron microscopic studies of the inner retina showed that Y1-immunostained amacrine cell processes and puncta received synaptic inputs from unlabeled amacrine cell processes (65.2%) and bipolar cell axon terminals (34.8%). Y1-immunoreactive amacrine cell processes most frequently formed synaptic outputs onto unlabeled amacrine cell processes (34.0%) and ganglion cell dendrites (54.1%). NPY immunoreactivity in the rat retina is distributed primarily to strata 1 and 5 of the IPL, and the present findings, thus, suggest that NPY acts in a paracrine manner on Y1 receptors to influence both horizontal and amacrine cells.
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Affiliation(s)
- Iona D'Angelo
- Department of Neurobiology, UCLA & VAGLAHS, Los Angeles, California 90095, USA.
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Simó R, Lecube A, Sararols L, García-Arumí J, Segura RM, Casamitjana R, Hernández C. Deficit of somatostatin-like immunoreactivity in the vitreous fluid of diabetic patients: possible role in the development of proliferative diabetic retinopathy. Diabetes Care 2002; 25:2282-6. [PMID: 12453974 DOI: 10.2337/diacare.25.12.2282] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To evaluate the vitreous levels of somatostatin-like immunoreactivity (SLI) in patients with proliferative diabetic retinopathy (PDR). RESEARCH DESIGN AND METHODS A total of 14 diabetic patients with PDR, in whom a vitrectomy was performed, were included in the study. Sixteen nondiabetic patients, with other conditions requiring vitrectomy, served as a control group. Both venous blood and vitreous samples were collected at the time of vitreoretinal surgery. Patients in whom intravitreous hemoglobin was detectable were excluded. In addition, a correction for plasma levels of SLI and intravitreal proteins was performed. SLI was measured by radioimmunoassay and vitreous hemoglobin by spectrophotometry. RESULTS SLI in the vitreous fluid was significantly lower in diabetic patients than in the control group (68 +/- 18.7 vs. 193.6 +/- 30.8 pg/ml, P < 0.01). The vitreous SLI-to-plasma SLI ratio was strikingly higher in nondiabetic subjects than in diabetic patients with PDR (5.3 [1.2-71.1] vs. 0.6 [0.03-4.1], P < 0.01). After correcting for total vitreous protein concentration, SLI (pg/mg of proteins) remained significantly higher in nondiabetic control subjects than in diabetic patients with PDR (186 [51-463] vs. 7.5 [0.8-82], P < 0.0001). Remarkably, intravitreous levels of SLI were higher than those obtained in plasma in nondiabetic control subjects (193.6 +/- 30.8 vs. 43.5 +/- 10.7 pg/ml, P < 0.0001). Finally, a lack of relationship between plasma and vitreous levels of SLI was observed in both diabetic patients with PDR and nondiabetic control subjects. CONCLUSIONS The significantly higher SLI in the vitreous fluid than in plasma detected in nondiabetic control subjects supports the concept that somatostatin plays a relevant role in retinal homeostasis. In addition, the intravitreous deficit of SLI observed in diabetic patients with PDR suggests that it might contribute to the process of retinal neovascularization.
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Affiliation(s)
- Rafael Simó
- Diabetes Unit, Division of Endocrinology, Hospital General Universitari Vall d'Hebron, Barcelona, Spain.
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Cristiani R, Petrucci C, Dal Monte M, Bagnoli P. Somatostatin (SRIF) and SRIF receptors in the mouse retina. Brain Res 2002; 936:1-14. [PMID: 11988224 DOI: 10.1016/s0006-8993(02)02450-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the retina, somatostatin (SRIF) acts as a neuromodulator by interacting with specific SRIF subtype (sst) receptors. The aim of this study was to detect mRNAs for sst(1-5) receptors by semiquantitative RT-PCR and to determine the cellular localization of either SRIF or individual SRIF receptor immunoreactivities. Size, density and absolute number of immunolabeled somata were measured using computer-assisted image analysis. With RT-PCR we found that all five sst receptor mRNAs were expressed, with highest levels of sst(2) and sst(4) receptors. SRIF immunolabeling was localized to sparse-occurring amacrine cells in the inner nuclear layer (INL) and to displaced amacrine cells in the ganglion cell layer (GCL). sst(2A) receptors were localized to protein kinase- (PKC) immunoreactive (IR) rod bipolar cells, calbindin- (CaBP-) IR horizontal cells, tyrosine hydroxylase- (TH-) IR amacrine cells and glycinergic amacrine cells. None of the sst(2A)-IR amacrine cells were found to express parvalbumin (PV) immunoreactivity. sst(4) receptor immunolabeling was localized to CaBP-IR and CaBP-non-IR cells in the GCL that originated long process bundles in the GC axon layer. These cells were not observed after optic nerve transection and they were therefore interpreted as ganglion cells. Quantitative analysis showed that all of the PKC-IR rod bipolar cells, CaBP-IR horizontal cells, and TH-IR amacrine cells and 5% of the glycinergic amacrine cells expressed sst(2A) receptors. In addition, 4-6% of the putative ganglion cells expressed sst(4) receptors. The localization of SRIF to sparse-occurring retinal neurons, together with the widespread expression of sst(2A) and sst(4) receptors suggests that SRIF acts at multiple levels of retinal circuitry. These results provide a database for investigations of the functional retinal networks in mice with genetic alterations of somatostatinergic transmission.
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Affiliation(s)
- Rosella Cristiani
- Dipartimento di Fisiologia e Biochimica 'G.Moruzzi', Università degli Studi di Pisa, Via S. Zeno, 31, 56127, Pisa, Italy
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