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Cifuentes F, Morales MA. Functional Implications of Neurotransmitter Segregation. Front Neural Circuits 2021; 15:738516. [PMID: 34720888 PMCID: PMC8548464 DOI: 10.3389/fncir.2021.738516] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Here, we present and discuss the characteristics and properties of neurotransmitter segregation, a subtype of neurotransmitter cotransmission. We review early evidence of segregation and discuss its properties, such as plasticity, while placing special emphasis on its probable functional implications, either in the central nervous system (CNS) or the autonomic nervous system. Neurotransmitter segregation is a process by which neurons separately route transmitters to independent and distant or to neighboring neuronal processes; it is a plastic phenomenon that changes according to synaptic transmission requirements and is regulated by target-derived signals. Distant neurotransmitter segregation in the CNS has been shown to be related to an autocrine/paracrine function of some neurotransmitters. In retinal amacrine cells, segregation of acetylcholine (ACh) and GABA, and glycine and glutamate to neighboring terminals has been related to the regulation of the firing rate of direction-selective ganglion cells. In the rat superior cervical ganglion, segregation of ACh and GABA to neighboring varicosities shows a heterogeneous regional distribution, which is correlated to a similar regional distribution in transmission strength. We propose that greater segregation of ACh and GABA produces less GABAergic inhibition, strengthening ganglionic transmission. Segregation of ACh and GABA varies in different physiopathological conditions; specifically, segregation increases in acute sympathetic hyperactivity that occurs in cold stress, does not vary in chronic hyperactivity that occurs in hypertension, and rises in early ages of normotensive and hypertensive rats. Given this, we propose that variations in the extent of transmitter segregation may contribute to the alteration of neural activity that occurs in some physiopathological conditions and with age.
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Affiliation(s)
- Fredy Cifuentes
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Miguel Angel Morales
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
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Barnerssoi M, May PJ, Horn AKE. GABAergic innervation of the ciliary ganglion in macaque monkeys - A light and electron microscopic study. J Comp Neurol 2017; 525:1517-1531. [PMID: 27864939 DOI: 10.1002/cne.24145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 10/19/2016] [Accepted: 10/23/2016] [Indexed: 11/09/2022]
Abstract
The vertebrate ciliary ganglion (CG) is a relay station in the parasympathetic pathway activating the iris sphincter and ciliary muscle to mediate pupillary constriction and lens accommodation, respectively. While the postganglionic motoneurons in the CG are cholinergic, as are their inputs, there is evidence from avian studies that GABA may also be involved. Here, we used light and electron microscopic methods to examine the GABAergic innervation of the CG in Macaca fascicularis monkeys. Immunohistochemistry for the gamma aminobutyric acid synthesizing enzyme glutamic acid decarboxylase (GAD) and choline acetyltransferase (ChAT) revealed that all CG neurons are contacted by ChAT-positive terminals. A subpopulation of 17.5% of CG neurons was associated with terminal boutons expressing GAD-immunoreactivity in addition. Double-labeling for GAD and synaptophysin confirmed that these were synaptic terminals. Electron microscopic analysis in conjunction with GABA-immunogold staining showed that (1) GAD-positive terminals mainly target dendrites and spines in the perisomatic neuropil of CG neurons; (2) GABA is restricted to a specific terminal type, which displays intermediate features lying between classically excitatory and inhibitory endings; and (3) if a CG neuron is contacted by GABA-positive terminals, virtually all perisomatic terminals supplying it show GABA immunoreactivity. The source of this GABAergic input and whether GABA contributes to a specific CG function remains to be investigated. Nevertheless, our data indicate that the innervation of the ciliary ganglion is more complex than previously thought, and that GABA may play a neuromodulatory role in the control of lens or pupil function. J. Comp. Neurol. 525:1517-1531, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Miriam Barnerssoi
- Institute of Anatomy and Cell Biology I, Ludwig-Maximilian Universität, Munich, Germany
| | - Paul J May
- Departments of Neurobiology and Anatomical Sciences, Ophthalmology, and Neurology, University of Mississippi Medical Center, Jackson, MS, 39216
| | - Anja K E Horn
- Institute of Anatomy and Cell Biology I, Ludwig-Maximilian Universität, Munich, Germany
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Malomouzh AI, Petrov KA, Nurullin LF, Nikolsky EE. Metabotropic GABAB
receptors mediate GABA inhibition of acetylcholine release in the rat neuromuscular junction. J Neurochem 2015; 135:1149-60. [DOI: 10.1111/jnc.13373] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 09/16/2015] [Accepted: 09/21/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Artem I. Malomouzh
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
| | - Konstantin A. Petrov
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- A.E. Arbuzov Institute of Organic and Physical Chemistry; Russian Academy of Sciences; Kazan Russia
| | - Leniz F. Nurullin
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- Kazan State Medical University; Kazan Russia
| | - Evgeny E. Nikolsky
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- Kazan State Medical University; Kazan Russia
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Rosa JM, Bos R, Sack GS, Fortuny C, Agarwal A, Bergles DE, Flannery JG, Feller MB. Neuron-glia signaling in developing retina mediated by neurotransmitter spillover. eLife 2015; 4. [PMID: 26274565 PMCID: PMC4566075 DOI: 10.7554/elife.09590] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 08/13/2015] [Indexed: 12/21/2022] Open
Abstract
Neuron-glia interactions play a critical role in the maturation of neural circuits; however, little is known about the pathways that mediate their communication in the developing CNS. We investigated neuron-glia signaling in the developing retina, where we demonstrate that retinal waves reliably induce calcium transients in Müller glial cells (MCs). During cholinergic waves, MC calcium transients were blocked by muscarinic acetylcholine receptor antagonists, whereas during glutamatergic waves, MC calcium transients were inhibited by ionotropic glutamate receptor antagonists, indicating that the responsiveness of MCs changes to match the neurotransmitter used to support retinal waves. Using an optical glutamate sensor we show that the decline in MC calcium transients is caused by a reduction in the amount of glutamate reaching MCs. Together, these studies indicate that neurons and MCs exhibit correlated activity during a critical period of retinal maturation that is enabled by neurotransmitter spillover from retinal synapses.
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Affiliation(s)
- Juliana M Rosa
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Rémi Bos
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Georgeann S Sack
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Cécile Fortuny
- Vision Science Graduate Program, University of California, Berkeley, Berkeley, United States
| | - Amit Agarwal
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, United States
| | - Dwight E Bergles
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, United States
| | - John G Flannery
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Marla B Feller
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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Abstract
Neurons that produce acetylcholine (ACh) are positioned to broadly influence the brain, with axonal arborizations that extend throughout the cerebral cortex, striatum, and hippocampus. While the action of these neurons has typically been attributed entirely to ACh, neurons often release more than one primary neurotransmitter. Here, we review evidence for the cotransmission of the inhibitory neurotransmitter GABA from cholinergic neurons throughout the mammalian central nervous system. Functional cotransmission of ACh and GABA has been reported in the retina and cortex, and anatomical studies suggest that GABA cotransmission is a common feature of nearly all forebrain ACh-producing neurons. Further experiments are necessary to confirm the extent of GABA cotransmission from cholinergic neurons, and the contribution of GABA needs to be considered when studying the functional impact of activity in ACh-producing neurons. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
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Affiliation(s)
- Adam J Granger
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Nicole Mulder
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Arpiar Saunders
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Bernardo L Sabatini
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA, USA.
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Katz E, Elgoyhen AB. Short-term plasticity and modulation of synaptic transmission at mammalian inhibitory cholinergic olivocochlear synapses. Front Syst Neurosci 2014; 8:224. [PMID: 25520631 PMCID: PMC4251319 DOI: 10.3389/fnsys.2014.00224] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/06/2014] [Indexed: 12/23/2022] Open
Abstract
The organ of Corti, the mammalian sensory epithelium of the inner ear, has two types of mechanoreceptor cells, inner hair cells (IHCs) and outer hair cells (OHCs). In this sensory epithelium, vibrations produced by sound waves are transformed into electrical signals. When depolarized by incoming sounds, IHCs release glutamate and activate auditory nerve fibers innervating them and OHCs, by virtue of their electromotile property, increase the amplification and fine tuning of sound signals. The medial olivocochlear (MOC) system, an efferent feedback system, inhibits OHC activity and thereby reduces the sensitivity and sharp tuning of cochlear afferent fibers. During neonatal development, IHCs fire Ca2+ action potentials which evoke glutamate release promoting activity in the immature auditory system in the absence of sensory stimuli. During this period, MOC fibers also innervate IHCs and are thought to modulate their firing rate. Both the MOC-OHC and the MOC-IHC synapses are cholinergic, fast and inhibitory and mediated by the α9α10 nicotinic cholinergic receptor (nAChR) coupled to the activation of calcium-activated potassium channels that hyperpolarize the hair cells. In this review we discuss the biophysical, functional and molecular data which demonstrate that at the synapses between MOC efferent fibers and cochlear hair cells, modulation of transmitter release as well as short term synaptic plasticity mechanisms, operating both at the presynaptic terminal and at the postsynaptic hair-cell, determine the efficacy of these synapses and shape the hair cell response pattern.
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Affiliation(s)
- Eleonora Katz
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Buenos Aires, Argentina ; Departamento de Fisiología, Biología Molecular y Celular "Prof. Héctor Maldonado", Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Buenos Aires, Argentina ; Tercera Cátedra de Farmacología, Facultad de Medicina, Universidad de Buenos Aires Buenos Aires, Argentina
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Activation of presynaptic GABA(B(1a,2)) receptors inhibits synaptic transmission at mammalian inhibitory cholinergic olivocochlear-hair cell synapses. J Neurosci 2013; 33:15477-87. [PMID: 24068816 DOI: 10.1523/jneurosci.2554-13.2013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The synapse between olivocochlear (OC) neurons and cochlear mechanosensory hair cells is cholinergic, fast, and inhibitory. The inhibitory sign of this cholinergic synapse is accounted for by the activation of Ca(2+)-permeable postsynaptic α9α10 nicotinic receptors coupled to the opening of hyperpolarizing Ca(2+)-activated small-conductance type 2 (SK2)K(+) channels. Acetylcholine (ACh) release at this synapse is supported by both P/Q- and N-type voltage-gated calcium channels (VGCCs). Although the OC synapse is cholinergic, an abundant OC GABA innervation is present along the mammalian cochlea. The role of this neurotransmitter at the OC efferent innervation, however, is for the most part unknown. We show that GABA fails to evoke fast postsynaptic inhibitory currents in apical developing inner and outer hair cells. However, electrical stimulation of OC efferent fibers activates presynaptic GABA(B(1a,2)) receptors [GABA(B(1a,2))Rs] that downregulate the amount of ACh released at the OC-hair cell synapse, by inhibiting P/Q-type VGCCs. We confirmed the expression of GABA(B)Rs at OC terminals contacting the hair cells by coimmunostaining for GFP and synaptophysin in transgenic mice expressing GABA(B1)-GFP fusion proteins. Moreover, coimmunostaining with antibodies against the GABA synthetic enzyme glutamic acid decarboxylase and synaptophysin support the idea that GABA is directly synthesized at OC terminals contacting the hair cells during development. Thus, we demonstrate for the first time a physiological role for GABA in cochlear synaptic function. In addition, our data suggest that the GABA(B1a) isoform selectively inhibits release at efferent cholinergic synapses.
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Raghu SV, Claussen J, Borst A. Neurons with GABAergic phenotype in the visual system of Drosophila. J Comp Neurol 2013; 521:252-65. [PMID: 22886821 DOI: 10.1002/cne.23208] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 03/16/2012] [Accepted: 08/03/2012] [Indexed: 12/11/2022]
Abstract
The visual system of Drosophila contains ~60,000 neurons per hemisphere that are organized in parallel, retinotopically arranged columns. The neuroanatomy of these neurons has been mapped in considerable detail at both the light and ultrastructural level. However, studies providing direct evidence for synaptic signaling and the neurotransmitter used by individual neurons are relatively sparse. Here we characterize those neurons in the Drosophila optic lobes that possibly release gamma aminobutyric acid (GABA), the major inhibitory neurotransmitter of the insect central nervous system. We identified 26 different types of neurons of the lamina, medulla, lobula, and lobula plate. Based on the previous Golgi-staining analysis (Fischbach and Dittrich [1989] Cell Tissue Res 258:441-475), the identified neurons are further classified into 11 major subgroups representing lamina monopolar (L), medulla intrinsic (Mi, Mt), bushy T (T), transmedullary (Tm), transmedullary Y (TmY), Y, lobula-complex intrinsic (Lccn), lobula columnar (Lcn), lobula plate intrinsic (Lpi), and lobula tangential (Lt) cell types. This detailed map of neurons with GABAergic phenotype will contribute to the future neurogenetic dissection of information processing circuits in the fly visual system.
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Affiliation(s)
- Shamprasad Varija Raghu
- Max-Planck-Institute of Neurobiology, Department of Systems and Computational Neurobiology, D-82152 Martinsried, Germany.
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Candidate glutamatergic neurons in the visual system of Drosophila. PLoS One 2011; 6:e19472. [PMID: 21573163 PMCID: PMC3088675 DOI: 10.1371/journal.pone.0019472] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 04/03/2011] [Indexed: 01/17/2023] Open
Abstract
The visual system of Drosophila contains approximately 60,000 neurons that are organized in parallel, retinotopically arranged columns. A large number of these neurons have been characterized in great anatomical detail. However, studies providing direct evidence for synaptic signaling and the neurotransmitter used by individual neurons are relatively sparse. Here we present a first layout of neurons in the Drosophila visual system that likely release glutamate as their major neurotransmitter. We identified 33 different types of neurons of the lamina, medulla, lobula and lobula plate. Based on the previous Golgi-staining analysis, the identified neurons are further classified into 16 major subgroups representing lamina monopolar (L), transmedullary (Tm), transmedullary Y (TmY), Y, medulla intrinsic (Mi, Mt, Pm, Dm, Mi Am), bushy T (T), translobula plate (Tlp), lobula intrinsic (Lcn, Lt, Li), lobula plate tangential (LPTCs) and lobula plate intrinsic (LPi) cell types. In addition, we found 11 cell types that were not described by the previous Golgi analysis. This classification of candidate glutamatergic neurons fosters the future neurogenetic dissection of information processing in circuits of the fly visual system.
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Li WC, Soffe SR, Roberts A. Glutamate and acetylcholine corelease at developing synapses. Proc Natl Acad Sci U S A 2004; 101:15488-93. [PMID: 15494439 PMCID: PMC524451 DOI: 10.1073/pnas.0404864101] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Most neurons release a single fast-acting low-molecular-weight transmitter at synapses to activate and open postsynaptic ion channels. We challenge this principle with evidence for corelease of the two major excitatory transmitters, glutamate and acetylcholine (ACh), from single identified neurons in the developing frog tadpole spinal cord. Whole-cell patch electrodes were used to record from single spinal neurons. When action potentials and inhibition were blocked, spontaneous miniature excitatory postsynaptic currents (mEPSCs) were recorded. These were fully blocked only by joint application of glutamate [alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and N-methyl-D-aspartate receptor (NMDAR)] and nicotinic ACh receptor (nAChR) antagonists. Fast nAChR and slow NMDAR mEPSCs were isolated pharmacologically. We then show that some mEPSCs have both the fast nAChR rise and slow NMDAR decay and conclude that some individual synaptic vesicles corelease glutamate and ACh. Whole-cell recordings from pairs of neurons were then used to identify the spinal interneurons coreleasing the two excitatory transmitters. One anatomical class of interneuron with descending axons was found to excite other spinal neurons by activating nAChR, AMPAR, and NMDAR simultaneously at its synapses. Although Jonas, Bischofberger, and Sandkuhler [Jonas, P., Bischofberger, J. & Sandkuhler, J. (1998) Science 281, 419-424] showed that the inhibitory transmitters GABA and glycine can be coreleased at spinal synapses, the Xenopus tadpole provides a case where the two main CNS excitatory transmitters are released from single vesicles, and where the presynaptic neuron coreleasing two transmitters has been identified.
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Affiliation(s)
- W-C Li
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, United Kingdom.
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YAMADA ELIZABETHS, DMITRIEVA NINA, KEYSER KENTT, LINDSTROM JONM, HERSH LOUISB, MARSHAK DAVIDW. Synaptic connections of starburst amacrine cells and localization of acetylcholine receptors in primate retinas. J Comp Neurol 2003; 461:76-90. [PMID: 12722106 PMCID: PMC3342658 DOI: 10.1002/cne.10672] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Starburst amacrine cells in the macaque retina were studied by electron microscopic immunohistochemistry. We found that these amacrine cells make a type of synapse not described previously; they are presynaptic to axon terminals of bipolar cells. We also confirmed that starburst amacrine cells are presynaptic to ganglion cell dendrites and amacrine cell processes. In order to determine the functions of these synapses, we localized acetylcholine receptors using a monoclonal antibody (mAb210) that recognizes human alpha3- and alpha5-containing nicotinic receptors and also antisera against the five known subtypes of muscarinic receptors. The majority of the mAb210-immunoreactive perikarya were amacrine cells and ganglion cells, but a subpopulation of bipolar cells was also labeled. A subset of bipolar cells and a subset of horizontal cells were labeled with antibodies to M3 muscarinic receptors. A subset of amacrine cells, including those that contain cholecystokinin, were labeled with antibodies to M2 receptors. Taken together, these results suggest that acetylcholine can modulate the activity of retinal ganglion cells by multiple pathways.
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Affiliation(s)
- ELIZABETH S. YAMADA
- Department of Neurobiology & Anatomy, University of Texas Medical School, Houston, Texas 77225
- Departamento de Fisiologia, Universidade Federal do Pará, Belém, Pará 66075-900, Brazil
| | - NINA DMITRIEVA
- Vision Sciences Research Center, University of Alabama, Birmingham, Alabama 35294
| | - KENT T. KEYSER
- Vision Sciences Research Center, University of Alabama, Birmingham, Alabama 35294
| | - JON M. LINDSTROM
- University of Pennsylvania Institute for Neurological Sciences, Philadelphia, Pennsylvania 19104
| | - LOUIS B. HERSH
- Department of Biochemistry, University of Kentucky, Lexington, Kentucky 40536
| | - DAVID W. MARSHAK
- Department of Neurobiology & Anatomy, University of Texas Medical School, Houston, Texas 77225
- Correspondence to: David W. Marshak, Department of Neurobiology & Anatomy, The University of Texas Medical School, P.O. Box 20708, Hous-ton, TX 77225.
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Sun H, Crossland WJ. Quantitative assessment of localization and colocalization of glutamate, aspartate, glycine, and GABA immunoreactivity in the chick retina. THE ANATOMICAL RECORD 2000; 260:158-79. [PMID: 10993953 DOI: 10.1002/1097-0185(20001001)260:2<158::aid-ar60>3.0.co;2-v] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We examined the posthatch chick retina for the frequency of occurrence of localization and colocalization of four amino acid transmitter candidates: glutamate (Glu), aspartate (Asp), gamma aminobutyric acid (GABA), and glycine (Gly) using postembedding methods. We support previous studies of Glu, Asp, GABA, and Gly localization in the direct and indirect functional pathways of the chick retina and extend these studies with new qualitative and quantitative observations. We found that photoreceptors show distinct cellular immunoreactivity for both Glu (Glu+) and Asp+, but not for Gly (Gly-) or GABA. Moreover, there is compartmentalization of Glu and Asp staining within the photoreceptors. All horizontal cells react strongly with Asp and Glu, about three-fourths are GABA+ and three-fourths of these are Gly+. Bipolar cells are uniformly Glu+, heterogeneously Asp+, occasionally Gly+, but GABA-. A majority of amacrine cells stain heterogeneously with all antibodies: 90% are Gly+, slightly more than half colocalize Glu, GABA, and Gly. Furthermore, amacrine cells in the outer two or three rows of cells are more likely to be stained by Gly than Glu, Asp, or GABA. Confirming previous studies, ganglion cells were mostly immunoreactive for Glu and Asp with fewer reactive for GABA and Gly. Strong and distinctly cellular immunoreactivity was found in both central and peripheral retina. Our findings show: 1) there is extensive colocalization of Glu, Asp, GABA, and Gly among most retinal neurons, including some cells that contain all four; 2) cells of the direct functional pathway tend to be labeled by Glu and Asp generally to the exclusion of GABA and Gly, while those of the indirect pathway tend to be labeled by GABA+ and/or Gly+ in addition to Glu+ and Asp+; 3) different cell body layers have distinct patterns of colocalization; and 4) there is no qualitative difference in staining patterns between peripheral and central retina.
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Affiliation(s)
- H Sun
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Caramelo OL, Santos PF, Carvalho AP, Duarte CB. Metabotropic glutamate receptors modulate [(3)H]acetylcholine release from cultured amacrine-like neurons. J Neurosci Res 1999; 58:505-14. [PMID: 10533043 DOI: 10.1002/(sici)1097-4547(19991115)58:4<505::aid-jnr4>3.0.co;2-j] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Retinal amacrine cells express metabotropic glutamate receptors (mGluRs), but their physiological role is unknown. We investigated the effect of mGluR on [(3)H]acetylcholine release ([(3)H]ACh) from cultured chick amacrine-like neurons. Activation of group III mGluR with the agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4) inhibited [(3)H]ACh release evoked by 25 mM KCl in a dose-dependent manner, and this effect was sensitive to pertussis toxin. In contrast, activation of group I or II mGluR with (S)-3, 5-dihydroxyphenylglycine (DHPG) and (2S,2'R,3'R)-2-(2', 3'-dicarboxycyclopropyl)glycine (DCG-IV), respectively, did not affect significantly [(3)H]ACh release. The effect of L-AP4 on [(3)H]ACh release was sensitive to nitrendipine, suggesting that it is, at least in part, due to inhibition of L-type Ca(2+) channels. Activation of group III mGluR also partly inhibited omega-conotoxin GVIA-sensitive Ca(2+) channels, coupled to [(3)H]ACh release. The L-AP4 did not affect the cAMP levels measured in amacrine-like neurons depolarized with 25 mM KCl or stimulated with forskolin, indicating that the effect of group III mGluR on [(3)H]ACh release is not due to inhibition of adenylyl cyclase activity. Inhibition of protein kinase A with KT-5720 was without effect on [(3)H]ACh release evoked by 25 mM KCl, further indicating that the effect of group III mGluR on [(3)H]ACh release cannot be attributed to the inhibition of the kinase. The effect of L-AP4 on [(3)H]ACh release was reversed by DHPG or by DCG-IV, and activation of group II mGluR also partially inhibited cAMP production stimulated by forskolin. Taken together, our results show that the effect of group III mGluR on [(3)H]ACh release may be due to a direct inhibition of L- and N-type Ca(2+) channels and is modulated by group I and group II mGluR.
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Affiliation(s)
- O L Caramelo
- Center for Neuroscience of Coimbra, Department of Zoology, University of Coimbra, Coimbra, Portugal
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