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Sharma K, Kang KW, Seo YW, Glowatzki E, Yi E. Low-voltage Activating K + Channels in Cochlear Afferent Nerve Fiber Dendrites. Exp Neurobiol 2022; 31:243-259. [PMID: 36050224 PMCID: PMC9471414 DOI: 10.5607/en22013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/18/2022] [Accepted: 07/29/2022] [Indexed: 11/19/2022] Open
Abstract
Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.
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Affiliation(s)
- Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Young-Woo Seo
- KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea
| | - Elisabeth Glowatzki
- Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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2
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Meredith FL, Rennie KJ. Persistent and resurgent Na + currents in vestibular calyx afferents. J Neurophysiol 2020; 124:510-524. [PMID: 32667253 DOI: 10.1152/jn.00124.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Vestibular afferent neurons convey information from hair cells in the peripheral vestibular end organs to central nuclei. Primary vestibular afferent neurons can fire action potentials at high rates and afferent firing patterns vary with the position of nerve terminal endings in vestibular neuroepithelia. Terminals contact hair cells as small bouton or large calyx endings. To investigate the role of Na+ currents (INa) in firing mechanisms, we investigated biophysical properties of INa in calyx-bearing afferents. Whole cell patch-clamp recordings were made from calyx terminals in thin slices of gerbil crista at different postnatal ages: immature [postnatal day (P)5-P8, young (P13-P15), and mature (P30-P45)]. A large transient Na+ current (INaT) was completely blocked by 300 nM tetrodotoxin (TTX) in mature calyces. In addition, INaT was accompanied by much smaller persistent Na+ currents (INaP) and distinctive resurgent Na+ currents (INaR), which were also blocked by TTX. ATX-II, a toxin that slows Na+ channel inactivation, enhanced INaP in immature and mature calyces. 4,9-Anhydro-TTX (4,9-ah-TTX), which selectively blocks Nav1.6 channels, abolished the enhanced INa in mature, but not immature, calyces. Therefore, Nav1.6 channels mediate a component of INaT and INaP in mature calyces, but are minimally expressed at early postnatal days. INaR was expressed in less than one-third of calyces at P6-P8, but expression increased with development, and in mature cristae INaR was frequently found in peripheral calyces. INaR served to increase the availability of Na+ channels following brief membrane depolarizations. In current clamp, the rate and regularity of action potential firing decreased in mature peripheral calyces following 4,9-ah-TTX application. Therefore, Nav1.6 channels are upregulated during development, contribute to INaT, INaP, and INaR, and may regulate excitability by enabling higher mean discharge rates in a subpopulation of mature calyx afferents.NEW & NOTEWORTHY Action potential firing patterns differ between groups of afferent neurons innervating vestibular epithelia. We investigated the biophysical properties of Na+ currents in specialized vestibular calyx afferent terminals during postnatal development. Mature calyces express Na+ currents with transient, persistent, and resurgent components. Nav1.6 channels contribute to resurgent Na+ currents and may enhance firing in peripheral calyx afferents. Understanding Na+ channels that contribute to vestibular nerve responses has implications for developing new treatments for vestibular dysfunction.
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Affiliation(s)
- Frances L Meredith
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado
| | - Katherine J Rennie
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado.,Department of Physiology & Biophysics, University of Colorado School of Medicine, Aurora, Colorado
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Identification of Persistent and Resurgent Sodium Currents in Spiral Ganglion Neurons Cultured from the Mouse Cochlea. eNeuro 2017; 4:eN-NWR-0303-17. [PMID: 29138759 PMCID: PMC5684619 DOI: 10.1523/eneuro.0303-17.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/13/2017] [Accepted: 10/17/2017] [Indexed: 01/11/2023] Open
Abstract
In spiral ganglion neurons (SGNs), the afferent single units of the auditory nerve, high spontaneous and evoked firing rates ensure preservation of the temporal code describing the key features of incoming sound. During postnatal development, the spatiotemporal distribution of ion channel subtypes contributes to the maturation of action potential generation in SGNs, and to their ability to generate spike patterns that follow rapidly changing inputs. Here we describe tetrodotoxin (TTX)-sensitive Na+ currents in SGNs cultured from mice, whose properties may support this fast spiking behavior. A subthreshold persistent Na+ current (INaP) and a resurgent Na+ current (INaR) both emerged prior to the onset of hearing and became more prevalent as hearing matured. Navβ4 subunits, which are proposed to play a key role in mediating INaR elsewhere in the nervous system, were immunolocalized to the first heminode where spikes are generated in the auditory nerve, and to perisomatic nodes of Ranvier. ATX-II, a sea anemone toxin that slows classical Na+ channel inactivation selectively, enhanced INaP five-fold and INaR three-fold in voltage clamp recordings. In rapidly-adapting SGNs under current clamp, ATX-II increased the likelihood of firing additional action potentials. The data identify INaP and INaR as novel regulators of excitability in SGNs, and consistent with their roles in other neuronal types, we suggest that these nonclassical Na+ currents may contribute to the control of refractoriness in the auditory nerve.
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The role of negative conductances in neuronal subthreshold properties and synaptic integration. Biophys Rev 2017; 9:827-834. [PMID: 28808978 DOI: 10.1007/s12551-017-0300-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/27/2017] [Indexed: 12/28/2022] Open
Abstract
Based on passive cable theory, an increase in membrane conductance produces a decrease in the membrane time constant and input resistance. Unlike the classical leak currents, voltage-dependent currents have a nonlinear behavior which can create regions of negative conductance, despite the increase in membrane conductance (permeability). This negative conductance opposes the effects of the passive membrane conductance on the membrane input resistance and time constant, increasing their values and thereby substantially affecting the amplitude and time course of postsynaptic potentials at the voltage range of the negative conductance. This paradoxical effect has been described for three types of voltage-dependent inward currents: persistent sodium currents, L- and T-type calcium currents and ligand-gated glutamatergic N-methyl-D-aspartate currents. In this review, we describe the impact of the creation of a negative conductance region by these currents on neuronal membrane properties and synaptic integration. We also discuss recent contributions of the quasi-active cable approximation, an extension of the passive cable theory that includes voltage-dependent currents, and its effects on neuronal subthreshold properties.
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Yao C, Vanderpool KG, Delfiner M, Eddy V, Lucaci AG, Soto-Riveros C, Yasumura T, Rash JE, Pereda AE. Electrical synaptic transmission in developing zebrafish: properties and molecular composition of gap junctions at a central auditory synapse. J Neurophysiol 2014; 112:2102-13. [PMID: 25080573 PMCID: PMC4274921 DOI: 10.1152/jn.00397.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 07/29/2014] [Indexed: 11/22/2022] Open
Abstract
In contrast to the knowledge of chemical synapses, little is known regarding the properties of gap junction-mediated electrical synapses in developing zebrafish, which provide a valuable model to study neural function at the systems level. Identifiable "mixed" (electrical and chemical) auditory synaptic contacts known as "club endings" on Mauthner cells (2 large reticulospinal neurons involved in tail-flip escape responses) allow exploration of electrical transmission in fish. Here, we show that paralleling the development of auditory responses, electrical synapses at these contacts become anatomically identifiable at day 3 postfertilization, reaching a number of ∼6 between days 4 and 9. Furthermore, each terminal contains ∼18 gap junctions, representing between 2,000 and 3,000 connexon channels formed by the teleost homologs of mammalian connexin 36. Electrophysiological recordings revealed that gap junctions at each of these contacts are functional and that synaptic transmission has properties that are comparable with those of adult fish. Thus a surprisingly small number of mixed synapses are responsible for the acquisition of auditory responses by the Mauthner cells, and these are likely sufficient to support escape behaviors at early developmental stages.
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Affiliation(s)
- Cong Yao
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Kimberly G Vanderpool
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and
| | - Matthew Delfiner
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Vanessa Eddy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Alexander G Lucaci
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Carolina Soto-Riveros
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Thomas Yasumura
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and
| | - John E Rash
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York;
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Sengupta B, Laughlin SB, Niven JE. Consequences of converting graded to action potentials upon neural information coding and energy efficiency. PLoS Comput Biol 2014; 10:e1003439. [PMID: 24465197 PMCID: PMC3900385 DOI: 10.1371/journal.pcbi.1003439] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 12/02/2013] [Indexed: 11/18/2022] Open
Abstract
Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na(+) and K(+) channels, with generator potential and graded potential models lacking voltage-gated Na(+) channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na(+) channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a 'footprint' in the generator potential that obscures incoming signals. These three processes reduce information rates by ∼50% in generator potentials, to ∼3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation.
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Affiliation(s)
- Biswa Sengupta
- Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
- Centre for Neuroscience, Indian Institute of Science, Bangalore, India
| | | | - Jeremy Edward Niven
- School of Life Sciences and Centre for Computational Neuroscience and Robotics, University of Sussex, Falmer, Brighton, United Kingdom
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Rash JR, Curti S, Vanderpool KGV, Kamasawa N, Nannapaneni S, Palacios-Prado N, Flores CE, Yasumura T, O’Brien J, Lynn BD, Bukauskas F, Nagy JI, Pereda AE. Molecular and functional asymmetry at a vertebrate electrical synapse. Neuron 2013; 79:957-69. [PMID: 24012008 PMCID: PMC4020187 DOI: 10.1016/j.neuron.2013.06.037] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2013] [Indexed: 12/20/2022]
Abstract
Electrical synapses are abundant in the vertebrate brain, but their functional and molecular complexities are still poorly understood. We report here that electrical synapses between auditory afferents and goldfish Mauthner cells are constructed by apposition of hemichannels formed by two homologs of mammalian connexin 36 (Cx36) and that, while Cx35 is restricted to presynaptic hemiplaques, Cx34.7 is restricted to postsynaptic hemiplaques, forming heterotypic junctions. This molecular asymmetry is associated with rectification of electrical transmission that may act to promote cooperativity between auditory afferents. Our data suggest that, in similarity to pre- and postsynaptic sites at chemical synapses, one side in electrical synapses should not necessarily be considered the mirror image of the other. While asymmetry based on the presence of two Cx36 homologs is restricted to teleost fish, it might also be based on differences in posttranslational modifications of individual connexins or in the complement of gap junction-associated proteins.
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Affiliation(s)
- John R. Rash
- Department of Biomedical Sciences and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado
| | - Sebastian Curti
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
- Laboratorio de Neurofisiología Celular, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Kimberly G. V. Vanderpool
- Department of Biomedical Sciences and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado
| | | | - Srikant Nannapaneni
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Nicolas Palacios-Prado
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Carmen E. Flores
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Thomas Yasumura
- Department of Biomedical Sciences and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado
| | - John O’Brien
- University of Texas Health Science Center, Houston, Texas, USA
| | - Bruce D. Lynn
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Feliksas Bukauskas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - James I. Nagy
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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Curti S, Hoge G, Nagy JI, Pereda AE. Synergy between electrical coupling and membrane properties promotes strong synchronization of neurons of the mesencephalic trigeminal nucleus. J Neurosci 2012; 32:4341-59. [PMID: 22457486 PMCID: PMC3339267 DOI: 10.1523/jneurosci.6216-11.2012] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 01/31/2012] [Accepted: 02/02/2012] [Indexed: 01/06/2023] Open
Abstract
Electrical synapses are known to form networks of extensively coupled neurons in various regions of the mammalian brain. The mesencephalic trigeminal (MesV) nucleus, formed by the somata of primary afferents originating in jaw-closing muscles, constitutes one of the first examples supporting the presence of electrical synapses in the mammalian CNS; however, the properties, functional organization, and developmental emergence of electrical coupling within this structure remain unknown. By combining electrophysiological, tracer coupling, and immunochemical analysis in brain slices of rat and mouse, we found that coupling is mostly restricted to pairs or small clusters of MesV neurons. Electrical transmission is supported by connexin36 (Cx36)-containing gap junctions at somato-somatic contacts where only a small proportion of channels appear to be open (∼0.1%). In marked contrast with most brain structures, coupling among MesV neurons increases with age, such that it is absent during early development and appears at postnatal day 8. Interestingly, the development of coupling parallels the development of intrinsic membrane properties responsible for repetitive firing in these neurons. We found that, acting together, sodium and potassium conductances enhance the transfer of signals with high-frequency content via electrical synapses, leading to strong spiking synchronization of the coupled neurons. Together, our data indicate that coupling in the MesV nucleus is restricted to mostly pairs of somata between which electrical transmission is supported by a surprisingly small fraction of the channels estimated to be present, and that coupling synergically interacts with specific membrane conductances to promote synchronization of these neurons.
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Affiliation(s)
- Sebastian Curti
- Laboratorio de Neurofisiología Celular, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay.
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Meredith FL, Li GQ, Rennie KJ. Postnatal expression of an apamin-sensitive k(ca) current in vestibular calyx terminals. J Membr Biol 2011; 244:81-91. [PMID: 22057903 DOI: 10.1007/s00232-011-9400-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 10/15/2011] [Indexed: 11/25/2022]
Abstract
Afferent innervation patterns in the vestibular periphery are complex, and vestibular afferents show a large variation in their regularity of firing. Calyx fibers terminate on type I vestibular hair cells and have firing characteristics distinct from the bouton fibers that innervate type II hair cells. Whole-cell patch clamp was used to investigate ionic currents that could influence firing patterns in calyx terminals. Underlying K(Ca) conductances have been described in vestibular ganglion cells, but their presence in afferent terminals has not been investigated previously. Apamin, a selective blocker of SK-type calcium-activated K(+) channels, was tested on calyx afferent terminals isolated from gerbil semicircular canals during postnatal days 1-50. Lowering extracellular calcium or application of apamin (20-500 nM) reduced slowly activating outward currents in voltage clamp. Apamin also reduced the action potential afterhyperpolarization (AHP) in whole-cell current clamp, but only after the first two postnatal weeks. K(+) channel expression increased during the first postnatal month, and SK channels were found to contribute to the AHP, which may in turn influence discharge regularity in calyx vestibular afferents.
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Affiliation(s)
- Frances L Meredith
- Department of Otolaryngology, University of Colorado at Anschutz Medical Campus, Aurora, CO 80045, USA
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Variability of distribution of Ca(2+)/calmodulin-dependent kinase II at mixed synapses on the mauthner cell: colocalization and association with connexin 35. J Neurosci 2010; 30:9488-99. [PMID: 20631177 DOI: 10.1523/jneurosci.4466-09.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In contrast to chemical transmission, few proteins have been shown associated with gap junction-mediated electrical synapses. Mixed (electrical and glutamatergic) synaptic terminals on the teleost Mauthner cell known as "Club endings" constitute because of their unusual large size and presence of connexin 35 (Cx35), an ortholog of the widespread mammalian Cx36, a valuable model for the study of electrical transmission. Remarkably, both components of their mixed synaptic response undergo activity-dependent potentiation. Changes in electrical transmission result from interactions with colocalized glutamatergic synapses, the activity of which leads to the activation of Ca(2+)/calmodulin-dependent kinase II (CaMKII), required for the induction of changes in both forms of transmission. However, the distribution of this kinase and potential localization to electrical synapses remains undetermined. Taking advantage of the unparalleled experimental accessibility of Club endings, we explored the presence and intraterminal distribution of CaMKII within these terminals. Here we show that (1) unlike other proteins, both CaMKII labeling and distribution were highly variable between contiguous contacts, and (2) CaMKII was not restricted to the periphery of the terminals, in which glutamatergic synapses are located, but also was present at the center in which gap junctions predominate. Accordingly, double immunolabeling indicated that Cx35 and CaMKII were colocalized, and biochemical analysis showed that these proteins associate. Because CaMKII characteristically undergoes activity-dependent translocation, the observed variability of labeling likely reflects physiological differences between electrical synapses of contiguous Club endings, which remarkably coexist with differing degrees of conductance. Together, our results indicate that CaMKII should be considered a component of electrical synapses, although its association is nonobligatory and likely driven by activity.
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Functional specializations of primary auditory afferents on the Mauthner cells: interactions between membrane and synaptic properties. ACTA ACUST UNITED AC 2009; 104:203-14. [PMID: 19941953 DOI: 10.1016/j.jphysparis.2009.11.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Primary auditory afferents are usually perceived as passive, timing-preserving, lines of communication. Contrasting this view, a special class of auditory afferents to teleost Mauthner cells, a command neuron that organizes tail-flip escape responses, undergoes potentiation of their mixed (electrical and chemical) synapses in response to high frequency cellular activity. This property is likely to represent a mechanism of input sensitization as these neurons provide the Mauthner cell with essential information for the initiation of an escape response. We review here the anatomical and physiological specializations of these identifiable auditory afferents. In particular, we discuss how their membrane and synaptic properties act in concert to more efficaciously activate the Mauthner cells. The striking functional specializations of these neurons suggest that primary auditory afferents might be capable of more sophisticated contributions to auditory processing than has been generally recognized.
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